Frequently Asked Questions

How do I know what model my Jeep® is?
Please visit our Jeep Identifier page to find out what Jeep® model you own.

Rich running Weber K551(K5534) carburetor . How do I lean the fuel mixture to remedy this problem?
The manufacturer states in the installation instructions that the fuel pressure at the carburetor inlet can not exceed (3.5 pounds). It is recommended that if you’re fuel delivery system is producing pressures above this mount a fuel regulator should be installed before the inlet. Pressure should be set at or around (3 pounds). It is also possible to swap out the main jet (size 65) with the secondary jet (size 47.5) to reduce the amount of fuel being delivered without affecting the overall performance of the carburetor. The carburetors are delivered from the manufacture preset to run rich. This is to reduce the likely hood of burning a piston due to a lean fuel mixture.

My 2.5L plastic valve cover bolt holes do not line up with the cylinder head. What should I do?
Do to the thermal dynamic nature of plastics the covers might have some natural deflection when they are released from the mold. When installing the 4cly valve cover you want to start the two front and two rear bolt holes first (finger start only. Do Not Tighten). This might require some force to be applied to help return the plastic to its original molded shape. After the front two and rear two bolts have been lined up and started the remainder bolt holes should align without any difficulty. Proceed with factory spec torque setting and pattern sequence. Please note that the replacement cover is supplied with a rubberized formed gasket attached to the cover. No additional gasket material is required. The replacement cover has been designed to work on two types of 2.5L heads that were supplied by Jeep®. The cover’s bolt hole openings might be larger than your original do to this variation from Jeep®.

Do the Dana Spicer axles that are for ABS applications come with the toothed sensor ring installed?
All Dana Spicer axles that are listed for use in ABS equipped Jeep® come with the toothed sensor rings already installed. They are part of the complete axle assembly when ordered using the correct part number.

What is the correct torque setting for the aluminum valve cover?
When installing the replacement aluminum valve covers for the 258 6 cylinder and the AMC V8’s you should follow the factory spec settings, and tighten in the correct sequence. It is important to note that the bolts should not be tightened past 55 INCH LBS. DO NOT TIGHTEN WITH A FOOT LBS TORQUE WRENCH as this will cause the aluminum covers to possible crack at the mounting holes. Resist the temptation to over tighten the gasket material. It can be squeezed out if too tight and allow for a possible leak. The original 6cly plastic valve cover calls for 28 in/lbs of torque to be applied but it will be OK to torque the new cover to 55 in/lbs.

How do I attach the Jeep® Nerf Bars to my vehicle?
Position Nerf bars to frame, front to back and parallel with the side and bottom of body. Mark holes with a center punch and drill (8 each side) 5/16” holes. Secure with self tapping bolts, supplied. It is advised to use two people when marking the positioning of the bars to frame for drilling.

There are no rear holes in the frame of my Jeep® to mount the Universal Rear Tow Hooks.
How do I mount them?
The rear universal mounted Jeep® tow hooks can be mounted on any flat surface of the frame on any vehicle using the supplied hardware. Once a location has been found, use the hooks as templates and drill two 1/2" holes in the frame (any existing holes in the frame can be used). Be sure to check for wires, fuel lines behind the frame before drilling. Torque supplied bolts to 65 ft/lbs.

The rear 7” extended fender flares I purchased for my CJ/YJ (Wrangler) do not match the existing mounting holes.
Did I get the wrong kit?
The CJ’s and YJ wrangler 7” fender flare kits both use the modern TJ rear flare. This rear extended flare allows for more room for taller and wider tires. A slight amount of trimming will be necessary to provide for a proper fit. A cardboard pattern, per the installation instructions, should be place on your Jeep® to mark were you will need to cut. When positioned correctly only the rear half of the wheel opening will need to be enlarged. If instructions are not available please contact the retailer you purchased your kit for a new copy.

I purchased a new spider gear set for my Dana 35 Trac-Lock, but the gears do not match my old set. Did I get the correct part?
The Dana 35 side gears and spider gears for the Trac-Lock are no longer machine cut. The machine cut gears are discontinued and are no longer being sold. The new design incorporates cast gears with a different tooth count than the older machined parts. If you are replacing any of these gears a complete new set will need to be ordered as they do not interchange.

What body parts from a CJ7 can I use as replacements for my CJ8?
A large number of CJ7 body parts are interchangeable with the longer wheelbase CJ8. All body panels forward of the firewall are the same including the windshield frame, and dashboard plate. After the firewall the front floor panel is also the same for both Jeep®, but this is were the similarities end. From the rear step-up back the bed of the CJ8 is 10” longer overall and has its own vehicle specific body panels. Please contact us for additional guidance or specific part numbers.

How do I know if I have an “L” flat head engine 4cly or the later “F” head over head valve 4cly engine in my vintage Jeep®?
The quickest way to determine what engine you have will be to look at the following items. “L” flat head engine will have the plugs and plug wires pointing straight up on top of the head. “F” head over head valve engine will have a metal valve cover and the plugs and wires will be pointing out at an angle on the driver’s side of the head. It is very important to know what engine you have before placing an order for parts. Your Jeep® might have had an engine replaced over the years that might not match your year’s specifications.

I’m installing the slip yoke eliminator kit onto my 231 transfer case and have found that the replacement main shaft is larger than my old unit. I can not reinstall the roller bearing back onto the shaft; did I get the wrong kit?
The slip yoke eliminator kit you have purchased has several improvements made to the unit including the main shaft that make it stronger than the parts you are replacing. The kit comes with the thicker main shaft that does away with the roller needle bearings all together. These parts will not be needed as stated in the installation instructions.

The replacement speedometer I purchased is not working correctly, why?
It is recommended that you purchase a new speedometer cable when you purchase a new speedometer. This item is often overlooked and what is thought to be an issue with the replacement speedometer may in fact be related to the cable. After installing the new speedometer double check all connections to the rear of the gauge and the cables attachment point at the transfer case. A bad cable will often produce a jumping effect or even a no read situation.

My new temp and or fuel gauge is not working correctly, why?
It is very important to install these items carefully and take the time needed to make sure that the wiring has been done correctly. If, after reading and connecting the gauges correctly per the installation instructions, you are still having problems than you might want to look at the following possibilities. If the gauge does not register than inspect the ground at the tank or the engine grounding strap (repair if needed). If the gauges work than repair or replace these grounding wires. If you are getting either a full or hot reading all the time than disconnect the sending unit wire at the tank or engine. If the gauge wire drops to empty or cold than replace the sending unit. If the gauge needles remain at full or hot than the gauge or sending wire has shorted. Check sending wire first for continuity issues. Due to the nature of this problem and the many different causes that might give faulty readings it is the installer’s responsibility to check all possible reasons before assuming a bad gauge is at fault. If you are still unable to correct your problem please contact the retailer you purchased the product from for further assistance. Here are the temperature gauge and fuel gauge calibration information for later CJ models with gauges inside of speedometer. TEMP = Cold (130-73 ohms) Beginning of band (171-36 ohms) Top of band (242-13 ohms) HOT (270-9 ohms) FUEL = Empty (73 ohms) 1/2 full (23 ohms) Full (10 ohms)

What is the ring tooth count for the GM 350 conversion flywheel (manual) that Omix sells (part number 16912.10)?
The flywheel we sell for the GM 350 conversion has a ring gear tooth count of 168. The flywheel is applicable for years 72-86. We do not stock a flywheel with a tooth count of 153.

What rear axle assembly do I have in my Jeep®?
Due to the length of production of the Jeep®, and the number of modifications that might have been made to any Jeep® over the years this question is a little harder to answer than most. The Dana-44 (flanged axle) was used for some 1986 CJ-7’s, and recently in some 1997-present TJ Wranglers. The AMC-20 (tapered axle) was used from 1976-1986 in CJ-5’s, and CJ-7’s. The Dana-35 (flanged axle) was used from 1987 to present in both Jeep® Wrangler models.

Can I use the T150 bell housing that Live Offroad sells with a T18 transmission?
Can I just drill and tap new holes?
The swap is possible but not without some modification work. The T150 bell housing can be used with some alteration if used with a Jeep® sourced T18 transmission. Alterations will include but not limited to drilling and tapping new lower mounting bolt holes for everything to line up correctly. It is important to note that further modifications will be needed if a Ford T18 is used, and it is quite possible that major reworking of the bell housing would be needed. Another problem to solve would be the need for a low profile bolt located just behind the clutch fork. If this bolt is not the correct size major problems with the fork not seating correctly on the pivot ball can accrue. As you can see there are a lot of variables involved with this type of switch and therefore Live Off Road does not note or promote the cross use of this bell housing for a T18 application. We will only be able to support and warranty the part for its original application and use.

What material are your fender flares made of, and do they have UV protection?
All of our fender flares are made of a plastic material called TPR (Thermoplastic rubber) and are UV protected. This is the same material that most front plastic bumpers are made of for good impact resistance.

Can I use any AMC V8 flywheel on any AMC V8 motor, and for any year?
The AMC V8's share a great number of parts between the different models (290,304,343,360,390, and 401's) but some items are motor specific. The flywheels are externally balanced for each motor and should not be swapped between motor sizes. OMIX sells the flywheels for the 1971 and up AMC 360 V8 (16912.08) and the 1971 and up 401 V8 (16912.09) These flywheels will not fit any motors produced before 1971 (different crank flange design) and should not be used on the smaller 304 V8.

My new OMIX Jeep® seats will not bolt to my stock CJ seat riser. Why?
The replacement OMIX Jeep® seats have been designed to work with a number of Jeep® mounting applications, but some additional hardware may be needed. If your OE CJ seat risers did not come with factory installed seat sliders these seats will not bolt directly to your frames. For proper fitment additional seat risers will need to be purchased and installed.

What gauge steel is used in the construction of your Jeep® body tubes?
Two gauges of steel are used in the construction of the reproduction body tubes. (18) Gauge steel is used in the front and rear flooring, all mounting brackets, top cowl assemble, and wheel housings. (16) Gauge steel is used for all side body panels and rear tail panels.

Can the bolt space pattern be changed on the Wheel Spacer Kit I purchased?
(15201.02, .03, .04, .05)
All bolt patterns are fixed and CANNOT be changed.

Does the heavy duty crossover steering kit (18050.82 and 18050.83) have replaceable tie rod ends?
All tie rod ends in this kit are replaceable. 18043.10 7/8" Tie Rod End Left hand thread 18043.26 7/8" Tie Rod End Right Hand Thread,18043.27 Tie Rod End with Drag Link Connection TJ-XJ Left hand threads, 18043.28 Tie Rod End with Drag Link Connection YJ Left hand thread. Part number 18043.10 is a stock part that can be found at most auto parts stores. It is used on 1991-2001 XJ (Cherokees) as the tie rods end link. Cross reference Jeep® part number (52005739).

How do I wire the dome light in the new sound bar I just purchased? The green wire gets wired to a switch,for example the door jamb switch. The red wire goes to a constant power source at the fuse panel. The black wire goes to a common ground. Note: There is no separate wiring harness for dome light wiring.

I have just purchased a new clutch kit for my Jeep. Why does the new clutch disc fit so loose on the splines of the input shaft?
Over time the input shaft can be worn down by the back and forth movement of the clutch disc on the input shaft. If your new clutch disc has an excessively loose fit, it is recommended that you replace the worn input shaft for proper clutch operation.

Article Source:
OMIX-ADA. Frequently Asked Questions. 2007-2008. http://www.omix-ada.com/faq.asp 23 Jan. 2009.

Jeep Off Roading
Be Prepared For Anything When You Go Off Roading

Off roading is an adrenaline rush like no other, except jeep off roading in snow. However, when off roading it is important to plan well and think of safety first, as with any extreme sport, injuries are always a possibility. With winter off roading, one has to take into account the severe cold temperatures and possibility of being stranded in such conditions. If hurt and stranded, this could be fatal.

When planning an off roading winter adventure there are some precautionary things to keep in mind and bring along. Recovery gear is essential in any off roading adventure, but even more so important with winter conditions. Make sure you have packed tow hooks, snatch straps, and winches. These will be your lifeline if stuck in 6 feet of snow. Snow shovels are also important to bring. When stuck in snow, sometimes it can be as easy a digging the snow away from around the tires, frame and axel for relief.

Make sure you know what you are driving into before charging in. It is easier to maneuver and get on top of packed or wet heavy snow then deep dry snow. Therefore, when facing 6 feet of dry snow, it is wise to reconsider unless your intent is to see how deep you can bury your jeep. Pay attention to the terrain around the trail as you go in and the weather. If it gets warm and snow begins to melt and get slushy, make sure your exit route is suitable for those conditions.

Have you ever heard the saying 'spinning your wheels in place gets you no where'? Well in jeep off roading, that saying could not be truer. When spinning your wheels you are digging your jeep in deeper then it already was. Let up on the throttle, try to back up turning wheel to find new track, if all else fails pull out the shovel or other recovery gear.

Make sure your jeep is equipped with tires to handle the snow. Wide flexible tires work well under snow off roading conditions. Bring along a mobile air tank for re-airing your tires. When off roading in snow, lowering the air pressure in your tires helps with surface contact. Keep all unnecessary stuff at home or off the trail. Keep your jeep as light as possible to stay on top off the snow. Dependent upon conditions you may even want to remove your hardtop.

Locking differentials are an advantage on snow. The ability to turn them on and off according to terrain needs will help in keeping your tires from spinning, or jeep from sliding down a hill. Make sure your coolant system is up for the challenge. Jeep off roading in snow is hard on an engines coolant system, especially if breaking new ground. Periodically check to make sure the radiator does not become packed with snow and coolant level is appropriate for temperatures of off roading location.

Make sure to dress appropriately for weather conditions. Bring along a sleeping bag, extra water, and some food. Always inform someone outside of your group what trails you intend on hitting and your expect arrival time home. Go jeep off roading with others for safety.

By following these simple tips, you can have an exciting time jeep off roading in the winter at exotic places such as Iceland, the Antarctica, Colorado, Maine, Canada, or Alaska. The locations are limitless for great times off roading in the snow.

Article Source:
Wendy Pan. “Jeep Off Roading - Be Prepared For Anything When You Go Off Roading.”
http://ezinearticles.com/?Jeep-Off-Roading---Be-Prepared-For-Anything-When-You-Go-Off-Roading&id=1629423 23 Jan. 2009.

Off Road Checklist

There is nothing worse than planning a great trip, getting out on the trail and finding out that you aren't prepared. Use the list below (I've arranged them in what I belive to be order of importance) to help pack your Jeep before heading out:

1. 1.) Tow hooks and strap
   On the trail, if you happen to get stuck, there's no good way to get you out without tow hooks and a strap. I have factory hooks installed on my front bumper, and have a hook that slides into my receiver hitch for the back.
2. 2.) Fire extinguisher
   No one wants to see their rig burn to the ground when a simple fire extinguisher would have prevented it.
3. 3.) Hi-Lift Jack
   The normal Jack that comes with your Jeep is fine for changing flats on the highway, but a Hi-Lift jack will allow you to do so much more. A Hi-Lift can help change tires and un-stick you when you are deep in a rut. Some newer jacks can even help you winch your truck.
4. 4.) First aid kit
5. 5.) Shovel
   Often, your Jeep will get stuck in a rut or hole. With a shovel, you'll be able to eith dig your truck out, or you will be able to move dirt / rocks so as to give your tires more bite.
6. 6.) Air pressure gauge and air compressor
   It is common to air down the tires in you Jeep when offroading (I like 17psi myself). An air gauge will allow you to run the correct pressure. One mistake that most people make is airing down without a good way to air back up, they end up running on the highway with only 15 psi, trying to get to the local gas station - not a safe situation.
7. 7.) Jumper Cables
   It's just too hard to push start a Jeep when you are stuck in a rut.
8. 8.) CB Radio
   I'm a big fan of CB radios, especially when it comes to offroading. It makes communicating with your buddies a breeze.
9. 9.) Motor Oil
   Extra motor oil can be helpful on the trail.

Article Source:
OffroadJeeps.com. “Offroad Checklist.” http://www.offroadjeeps.com/offroad-checklist.html 23 Jan. 2009

Off-Roading Tips
Emergency Supplies

Assemble the following items in a storage container to keep on-board. Be sure to tie down and secure all items in your vehicle. Loose tools and spare parts can become dangerous projectiles if the vehicle stops suddenly or encounters large bumps along the way. While chances are slim that you'd actually need them, you should pack enough food and camping equipment to be able to stay alive and relatively comfortable for several days in adverse conditions. Other items to include:

• a good hydraulic jack (and a piece of thick plywood for a jack base)
• first aid kit (suntan lotion, insect spray, burn ointment, ace bandage, iodine, bandages)
• packable foods - Army surplus stores carry them
• compass (or GPS if you can afford one)
• regional guidebooks to help you located off-road trails
• flashlight or lantern (check the batteries before you go)
• waterproof matches
• pocketknife
• blanket
• shovel
• towrope
• 2 boards (about 2-feet long)
• aerial or road flares
• duct tape
• electrical tape
• tarp or ground cover
• at least 1 gallon of water per person
• mobile phone (but remember that mobiles have limited coverage)
• maps, trail guides
• fire extinguisher
• air compressor (aerosol "fix-a-flat" works well in a pinch)
• 2 gallons of water for the radiator (not antifreeze).
• 1 gallon of engine oil
• 2-quarts 80/90w gear oil for diff's and transfer
• 5 gallons of spare gas/diesel
• 1-pint brake fluid & funnel for all fluids
• an axe
• if you'll be riding in dunes, take along a flag so people can see you
• washer fluid
• garbage bags
• towels, rags
• bungee cords
• snow chains with tensions (correct sizes with rubber or spring straps, not cable-chains!)
• 2 D-ring shackles
• a recovery strap
• tow hooks properly mounted to your 4x4
• gloves
• basic tool kit
• spark-plug socket
• jump leads
• tire pressure gauge
• some key spare parts
• 8000-lbs winch and winch kit
• appropriate manuals for your vehicle for quick repairs
• rain suit
• spare warm clothing (even in summer; temperatures fall dramatically after dark)

When the fun is over and done, the work has yet to begun. You need to take care of your vehicle so it will take care of you on your next off-road adventure. Some important things to do:

When returning to the road, first disengage the diff lock (if applied). Then stop and take the time to check your vehicle for any minor damage. Check for cuts to the tires, bent steering rods and debris that might have become lodged in the underside of the vehicle. Check for body damage that will rub against tires or be a hazard to others, and remove mud stuck to the wheels (which causes tire imbalance).

After you return home, service your 4x4. Fluids and filters need to be changed more often when you drive on rough terrain. Transmissions, transfer gearboxes, differentials, hubs and brakes can be contaminated with mud and water. These parts need to be cleaned and serviced when used under such conditions.
Article Source:
Jim Walczak. “Off Roading Tips.” Emergency Supplies. http://4wheeldrive.about.com/cs/offroadingtips/a/aa020401f.htm 23 Jan. 2009

Off-Road 4x4 Glossary

ABS. Anti-lock braking system; prevents wheels locking under maximum braking. Works on the principle of braking a wheel until it just begins to skid (this is the point where braking efficiency would drop off dramatically) and then releasing the brake pressure and re-applying the brakes. Wheel speed sensors identify the skid point and trigger a release in brake pressure. The cycle is repeated many times a second -with appropriate 'cobblestone' feed-back on the brake pedal to indicate you are in ABS mode. See also 'Cadence braking'.

Approach angle. In side-view, the angle between the ground and a line, ahead of the vehicle, joining the periphery of the front wheel and (typically) the front bumper or other low component. It represents the size or steepness of a slope or obstacle that can be approached or climbed without striking bodywork.

Articulation. The ability of one axle to move - left wheel up, right wheel down or vice versa - relative to the chassis or its fellow axle. It is a measure of the ease with which wheels can stay in contact with the ground - and thus retain traction - on very 'twisty' off-road terrain.

Articulation angle, longitudinal. See 'Longitudinal articulation angle', wheels run within rigid casings without joints to allow vertical hinging as with independent suspension. In an off-road vehicle rigid axles have the advantage of maintaining maximum under-axle ground clearance at all times and always keeping the tire tread flat on the ground.

Bridle. A rope or cable attached to two points - typically the right and left chassis members - of a vehicle and converging to a point of attachment for a tow rope.

Cadence braking. A method of manual braking with the foot brake to simulate the action of ABS brakes - see above. Very effective in slippery conditions where brake locking has occurred or might otherwise occur, the driver applies the footbrake in a series of very rapid jabs at the pedal taking the wheels up to the point of brake locking and then releasing them before the inevitable fall-off in braking efficiency takes place. Effects improved braking in any extremely slippery conditions such as ice, snow, wet mud, or rain.

Capstan winch. A winch, generally mounted on or just behind the front bumper, usually run from an engagable extension to the engine crankshaft. The active component is usually a slowly revolving drum, about 15 cm in diameter, round which a rope may be wound to effect a winching operation. Has the advantage of being powered by the engine at idling speed and being a very low-stress unit that may be used all day without overheating or high electrical load.

Castor (or caster) angle. When the front wheels are moved right or left to steer the vehicle they each move about a steering axis. The aft inclination of this steering axis from the vertical (when viewed from the side) - about in the case of most Land Rovers - is the angle. Like casters on a tea trolley or office chair, this puts the ground contact point of the wheels the pivot axis and the result is a self-centering action tending to keep the front wheels pointing forward when in forward motion. Note that in deep sand with a 'bow wave' build-up of sand ahead of the wheels the effective ground contact point moves ahead of the steering axis and can give the effect of negative castor with runaway' steering. The same thing happens when vehicle is travelling in reverse - the ground contact point being 'ahead' of the steering axis and again tending to make the front wheels 'run away' to full lock, failed climbing of steep off-road inclines.

Castor action. Tendency of front wheels to self-centre when the steering wheel is released with the vehicle going forward. NB Opposite action takes place when in reverse - see Castor angle above. Castor action is a basic ingredient of steering feel.

Centre differential. A differential gear device installed at the point where the transfer box splits engine power between the front and rear axles via the front and rear propeller shafts. Working in the same way as the conventional rear axle differential on a two-wheel drive car, it allows differential rotation of front and rear shafts to accommodate the small rotational differences encountered in normal running, going round sharp corners etc. Such a device is essential in a vehicle having - for use on-road as well as off-road - full-time or permanent 4x4. Vehicles fitted with part-time or selectable 4x4 are not fitted with centre differentials and thus cannot be used in four wheel drive on hard roads.

Continuous rolling contact. Description of a wheel in steady rolling contact with the ground without slip, wheel-spin or slide (as with locked brakes). Should be the aim at all times both on and off road.

Cross ply tire. Tire in which the sidewall reinforcement plies run diagonally from the bead towards the tread - each layer of textile at a different angle to its adjacent layer. Generally superseded by radial-ply tires whose thinner, more flexible sidewalls and braced tread yield better grip and lower rolling resistance. Because of thicker, multi-ply sidewalls, not so prone to sidewall damage as radials and can have low-cost applications when operating continuously on rock. However, reduced pressures in soft going can, due to the thick sidewalls, cause overheating and possibly de-lamination of the tire.

Co-ordinated tow. When recovering a stuck vehicle, the process by which the engine power of both the tug and the stuck vehicle are co-ordinated - usually by a signal from an external marshaller - and the clutches of both vehicles are engaged at the same time to enhance the chance of a first-time recovery.

Corrugations. Deformation of an unsurfaced track taking the form of transverse, close-pitch undulations - ie at right angles to the direction of the track. Sometimes referred to as 'washboard'.

Coupled brakes. Brake system installed with certain large trailers whereby the trailer brakes are applied at the same time as are the brakes of the towing vehicle. Vehicles must be specifically modified to operate this system - with appropriate trailers.

Departure angle. In side view, the angle between the ground and a line, aft of the vehicle, joining the periphery of the rear wheel and (typically) the rear chassis member or other low component. It represents the size or steepness of a slope or obstacle that can be approached or climbed in reverse without striking bodywork.

Diagonal suspension. A manifestation occurring off-road when a vehicle is, for example, diagonally crossing a small but well-defined ridge. When the ridge is so severe that, say, the right front wheel and the rear left wheels are on full 'bump' (ie fully up in the wheel arches) and the other wheels are hanging down to the full extent of wheel travel, the vehicle may be described as being diagonally suspended or on diagonal suspension. Some also refer to this state as being 'cross-axled'.

Diagonal wheel-spin. The wheel-spin that can take place on the fully extended wheels in a condition of diagonal suspension as described above. However, a vehicle need not be in a totally diagonal suspension condition for diagonal wheel-spin to take place; minor off-loading of diagonally opposed wheels or the presence of slippery ground under these wheels can provoke the condition. Can also occur crossing ditches diagonally.

Diff-lock. See first 'Centre differential' above. Locking of the centre differential, activated by moving the transfer gearbox lever to the left and confirmed by illumination of the 'DIFF-LOCK' indicator light, puts the differential function on hold. Where traction conditions or grip are different front and rear there would be a tendency for the centre differential to permit the front wheels, say, to spin ineffectively while they are on wet clay and cause the rear wheels, on grippier ground, to stop rotating. The diff-lock locks the centre differential, thus locking front and rear prop shafts together, ensuring they revolve at the same speed and enhancing traction. Diff-lock is usually engaged for difficult off-road conditions but should never remain engaged on hard grippy roads.

Differential casing. Not to be confused with the centre differential, each axle, of course, has a normal cross-axle differential at the point where the propeller shaft from the transfer gearbox meets the axle. The size of the crown wheel and pinion plus differential demands a bulge in the axle casing - referred to as the diff casing. It has special significance in off-road vehicles because it is the lowest point of the axle and thus the point of least ground clearance -

Discontinuity of rolling contact. Generic term for wheel-spin and wheel slide - as on locked brakes. See 'Continuous rolling contact' above.

EAS - electronic air suspension. Introduced in the 1993 model year on certain Range Rover models further to enhance standards of road noise insulation, ride and handling, the system substitutes air bags and a live-line pneumatic system, (ie an electrically driven compressor, air pressure reservoir and associated controls) for the steel coil springs used on the rest of the Land Rover model range. Logic- controlled by an electronic control unit, height sensors and driver controls, the system maintains front and rear self-levelling in the five height modes listed below. These notes show the versatility of the system and the purpose for which it was designed. However, for the casual driver, new to the vehicle, no prior knowledge or expertise is required; FAS will cycle automatically through appropriate modes according to prior programming. The driver need not even know EAS is fitted. On engine start-up EAS assumes the last selected ride height.

Electronic traction control - ETC. ETC is a standard/optional feature, available only on ABS-equipped Range Rovers. It inhibits wheel-spin by applying brake to a spinning rear wheel and thus enhances traction on ice, snow or in severe off-road conditions. It utilises ABS sensors for wheel speed determination and brakes the spinning wheel to, through the axle differential, apply torque to the stationary wheel. Like ABS. it is especially effective in maintaining control when one side of the vehicle is on a more slippery surface than the other - a so-called 'split-p surface. A dashboard light illuminates when the system is operating. The function is inhibited above 50 kph, a speed above which unintentional wheel spin is unlikely to occur.

Engine braking. Vehicle retardation derived from engaging a low gear and taking your foot off the throttle.

Emergency flotation (pressure). Very low tire pressure (about 60% of normal road pressures), always associated with a low maximum permitted speed (20 kph or 12 mph) used for traversing or recovery from very soft ground. Such low pressures cause extreme tire sidewall flexing - hence the speed limitation.

Emergency soft. Another name for emergency flotation tire pressure - see above.

Fatigue life. Number of specified load reversals at which a metal component will fail. In the context of this book see fatigue life of nylon snatch-towing ropes -'Recovery - snatch-towing'.

Flotation. Characteristic of a vehicle, by reason of large softly inflated tires, not to sink on soft going such as mud or sand.

Four-wheel drive (4x4). Vehicle transmission system in which engine power is applied to all four wheels. The term 4x4 (four by four) has the specific connotation that it is a four (wheeled vehicle driven) by four (wheels).

Full-time 4x4. A transmission system on a four-wheeled vehicle in which all four wheels are driven by the engine all the time. (As opposed to a vehicle that is normally in two-wheel drive with four-wheel drive selected by a separate lever when required.)

Geometric limitations. A term coined for this book to describe the limitations and extent of approach and departure angles, ramp angle, steering lock, articulation and - an even newer term - longitudinal articulation angle.

Ground clearance. Space between the ground and a given mechanical part of the vehicle. Usually, when quoted for a vehicle, taken as the least for any component on the vehicle - the space under the differential casing. But note difference between under-axle and underbelly clearance.

Ground stress. Term coined for this book to indicate how much strength is being asked of a particular piece of ground in terms of flotation or lateral shear to accommodate traction, braking or acceleration.

Heel and toe wear. Jargon for the uneven front to rear wear on individual blocks of a bold off-road tire tread when used on roads.

High box. Status of the transmission when the two-speed transfer gearbox lever is in the high ratio position - for normal, on-road, day-to-day use.

High ratio. Term to describe the transmission when the transfer gearbox lever is in the high position - high box above.

Hi-lift jack. Versatile lever-operated mechanical bumper jack capable of a lift of a metre or more.

Hi-lo lever. Term sometimes used to describe the transfer gearbox lever. High Load suspension. An option on the Defender 90 enabling payload to be raised by about 150 kg.

Kerb weight. Unladen weight, ie empty vehicle plus full fuel plus 75 kg driver.

KERR. Kinetic Energy Recovery Rope. Descriptive term coined to describe specially specified nylon ropes capable of stretching during snatch tow.

GVW. Gross vehicle weight - the maximum permitted laden weight of a vehicle including payload, fuel and driver.

Kinetic energy. Energy of motion, proportional to the total weight of the vehicle and the square of its speed. Thus if a vehicle's weight doubles its KE also goes up two times; but if its speed doubles its KE increases by two squared, ie four times. See 'Recovery - snatch-towing'

Laden. Vehicle carrying some or full payload. See also GVW above concerning loading to maximum permitted weight.

Levelled suspension. A means of eliminating the 'squat' of the rear suspension under load by a hydraulic self-levelling unit between the chassis and the centre of the rear axle.

Longitudinal articulation coefficient (CLA) single number that conveys the off-road, 'twisty ground' potential of an off-road vehicle. A given max wheel movement enhances this capability more on a short wheelbase than on a long wheelbase vehicle. (CLA) is a non-dimensional parameter, provisionally coined, (higher values mean better articulation) that takes account of both wheel movement and wheelbase; it relates to the angle between the ground and a line joining the front and rear hubs (or tyre periphery) when one wheel is on full bump and the other fully.

Low box. Status of the transmission when the transfer gearbox lever is in the low position - for difficult off-road conditions demanding greater traction or low speed control.

Low ratio. Term to describe the transmission when transfer gearbox lever is in the low position.

Marshalling. ('Marshaller' derived from ground-crew who marshal aircraft on airport aprons.) In the context of off-road operations, taken to mean the detailed direction of a vehicle by a marshaller outside the vehicle who is able to see all four wheels and also the difficult ground being traversed. Marshalling should be undertaken when there is the danger of damaging tyre sidewalls or the underside of the vehicle on rocks or other obstacles.

M+S tyres. Mud and snow tyres. A generic term for 4x4 tyres with a road-oriented, not especially bold, tread pattern suitable for mild snow and mud conditions.

Mud tyres. Bold, open-tread tyres optimised for mud with disadvantages on hard roads.

Multi-purpose tyre. Combination / compromise between on-road and mud tyres.

NATO towing hook. Large, robust, four-bolt attachment towing pintle with top-closure and, usually, 3600 rotational capability about the longitudinal axis originally specified for NATO 7.5 tonne military vehicles. Suitable for off-road towing albeit, due to the fact that a trailer towing eye will not be a close fit over the hook, it generates quite a bit of 'goods train' fore and aft banging.

Nose load. Trailers should be nose heavy; the nose-load is the amount of nose-heaviness (sometimes called trailer preponderance') measured at the tow-hitch and must be considered part of the towing vehicle's payload.

On-foot recce. Inspecting a difficult off-road obstacle on foot before committing your vehicle to it.

Overrun brakes. Trailer brakes activated by the tendency of the trailer to overtake -or overrun - the towing vehicle when the vehicle brakes or slows down.

Over-torque. Used in this book to convey the concept of applying too much torque (or power) to the wheels so that they break their grip with the ground and spin. Radial ply tyre. A type of tyre construction in which sidewall structural plies run radially out towards the tread instead of criss-cross diagonally. With their thinner, more flexible sidewalls, radial tyres have lower rolling resistance than cross-ply tyres (yielding better fuel consumption) as well as giving longer tread life. They can accommodate the use of low inflation pressures without overheating, due to their flexible sidewalls, but are sometimes more prone to sidewall damage when operating in rocky or stony conditions. Because radial tyres invariably also have a braced tread area of great dimensional stability, they 'track-lay' the tread (like a bulldozer), do not suffer from 'tread shuffle' and so achieve more traction in limiting off-road conditions.

Ramp angle. A measure of vehicle under-belly clearance or the ability to drive over a sharp ridge or ramp without touching the underside of the vehicle on the obstacle. The ramp angle is the angle measured from the lowest part of the chassis at mid-wheelbase down to the periphery of front and rear wheels. Obviously a short wheelbase vehicle with large wheels will have the smallest ramp angle and best under-belly clearance.

Ramp breakover angle. The fuller title of 'Ramp angle' above.

Range change. Term sometimes used for the transfer gearbox lever.

Reduced inflation. Lowering tyre pressures to increase flotation in soft ground conditions such as mud or soft sand.

Sand ladders. A pair of aluminium ladders, about 170 cm long, specially made with rungs closer than normal, to lay beneath the vehicle wheels in soft sand to give grip and flotation.

Sand tracks. Generic name sometimes given to any item fulfilling the role of a sand ladder. May be PSP (pierced steel planking).

Sand channels. Term often interchangeable with sand tracks, channels were used for this purpose. Can include articulated sand planks.

Sand tyres. Term often used to mean desert tyre - implying an ability to cope with desert rock and stones as well as sand. These tyres are characterised by tread blocks of a gentle, shouldered profile with no bold, right-angled edges such as a mud tyre would have. Radial construction is far more suited to the low inflation pressures sometimes used in sand. Despite their appearance, 'balloon' tyres with circumferential groove treads are considerably less effective in sand than a radial such as the Michelin XS.

Salt flat. Salt marsh of very unreliable consistency and bearing strength found in desert regions and characterised by a top crust of varying thickness and strength with soft salt mud of great depth beneath it.

Selectable four-wheel drive. A four-wheeled vehicle which proceeds normally in two-wheel drive but on which, by means of a lever control, four-wheel drive may be selected. It is important to remember that such vehicles in four-wheel drive do not have the benefit of a centre differential.

Self centring. The characteristic of front (steered) wheels to resume the straight-ahead position due to castor angle (See 'Castor angle') when the steering wheel is released. This characteristic can be utilised to enhance safety when driving in deep wheel ruts on slippery ground.

Sidewall. The external 'walls' of a tyre between the tread and the bead or wheel rim. This area is particularly vulnerable on radial ply tyres to damage in off-road operations from oblique rubbing contact with side-swiping sharp rocks. Driver awareness is essential.

Sidewall awareness. Awareness by sensitive drivers of the susceptibility to damage of the tyre sidewall. An attribute worth developing.

Sidewall deflection. Outward movement of the tyre sidewall in the region of the ground contact patch due to low inflation pressures or hitting a sharp bump with excess speed. It is important not to run tyres at less than recommended inflation pressures for given maximum speeds and loads since by doing so you will exceed the manufacturer's specified limits for sidewall deflection and thus cause overheating and serious damage to the tyre.

Shock loading. In the context of this book, taken to mean the arrest of mechanical motion in an excessively abrupt way or the application of sharp load reversals in a such a way as to risk structural failure. For example, the application of the handbrake whilst the vehicle is in motion can cause unacceptable shock loading of the rear axle half-shafts. Engaging diff-lock whilst one or more wheel is spinning could also result in severe and damaging shock load to the transmission.

Small gear lever. Don't be embarrassed if you can't remember the name for the transfer gear lever..!

Snatch tow. A method of recovering a stuck vehicle in which the towing vehicle is in motion before taking up the slack in the tow rope. Use only using special-purpose stretch ropes and specified procedures for this.

Steering lock. The extent to which the steering wheel may be moved to the right or left. Thus 'full lock' implies movement of the steering wheel as far as it will go right or left.

Stretch limit (KERR ropes). The extent to which a kinetic energy recovery rope will stretch before it is in danger of breaking. A gnide for the Marlow Ropes Recovaline is 40% stretch; this limit should NEVER be approached.

Traction. In the context of this book the concept of achieving grip between the wheels and the ground without slip, skid or sinkage.

Traction Control. See 'Electronic Traction Control, ETC'.

Traction controls. Here taken to mean the lever controlling the transfer gearbox and centre differential lock.

Tractive effort. The amount of 'pull' exerted by a vehicle as a result of traction.

Trailer preponderance. Sometimes used to denote down-load on the vehicle towing hitch.

Transfer box. Originally the name implied the transfer of power from the main gearbox to the front axle as well as the rear axle on a four-wheel drive vehicle. In all Land Rover products a two-speed transfer box is fitted so it has the additional role of permitting power from the gearbox to go to the axles at normal 1:1 gearing (high ratio) or geared down by nearly 2:1 (low ratio).

Transfer Gear Lever. The small gear lever in the cab next to the main gear lever. It controls whether the transmission is in 'high ratio' or 'low ratio' in the transfer box. The same lever also controls the engagement of the diff lock - see above -except in the Range Rover where a viscous coupling fulfils this requirement automatically.

Transmission brake. The handbrake on all Land Rovers operates by gripping the rear propeller shaft at the point where it leaves the transfer gearbox and is thus called a transmission brake. It should be used as a parking brake only and should never be operated whilst the vehicle is in motion except in emergency.

Transmission wind-up. Read first 'Centre differential',. A 4x4 with no centre differential or one driven with the centre diff locked (ie in both cases the front and rear propeller shafts locked together) is unable to accommodate the small differences in distance normally travelled by the front wheels compared to the rear wheels. The diff-lock ensures both propeller shafts rotate exactly the same amount despite the small differences in distance actually travelled. This results in some wheel slip and skid which, on loose ground, can take place without any harm. On hard roads, however, the superior wheel grip makes it difficult for the wheels to slip much and in the process of trying to do so considerable torsional stress builds up in the transmission. This is known as transmission wind-up and can sometimes exert so much stress that the diff-lock gears will not disengage when so selected. You will also sense very heavy steering. If this occurs due to your forgetting to de-select diff-lock on hard ground (or at any other time) and the diff lock will not disengage, the solution is to reverse the vehicle some distance until the diff-lock warning light extinguishes.

Unladen. Vehicle carrying fuel, driver but no payload or other load - see 'Kerb' above.

Viscous coupling unit (VCU). A unit fitted as standard to all Range Rovers across the centre differential (not instead of it) automatically to effect locking of the differential when a significant speed difference between front and rear propeller shafts is sensed. Conceptually it comprises a cylinder attached to the rear prop shaft into which an extension of the front prop shaft is introduced. Discs are attached alternately to the front prop shaft and the inside of the cylinder so that they interleave very closely within the cylinder. The cylinder is sealed at both ends and is filled with a special silicone fluid which has the characteristic of markedly increasing its viscosity when stirred. Thus when one prop shaft rotates relative to the other one - the situation of front (or rear) axle wheel-spin - the fluid increases its viscosity enough to lock the shafts together. When relative rotation ceases the viscosity changes back to its original value and the shafts are unlocked. The viscous coupling unit (VCU) has the advantage of being automatic on both engagement and disengagement and its action is gradual and without shock-loading to the transmission.

Wading plugs. Oil drain holes are provided in the bottom of the clutch housing (and the camshaft drive-belt housing on Tdi and 2.5D engines) to preclude the possibility of the clutch or cam belts becoming contaminated in the event of oil leaks from the adjacent bearings. Wading plugs should be fitted to block these holes when driving through water over 30 cm deep and subsequently removed.

Article Source:
Wood Park Off-Road. Off-Road 4x4 Glossary. 2009. http://www.woodpark-offroad.com/off-road-4x4_glossary.php 23. Jan