An Archive for Fanatics of Land Rovers

An Archive for Fanatics of Land Rovers










Land Rover Diff Conversion - Differential Locker

KAM Diff Locker | Detroit Tru Track Differential Locker | ARB Air Locker

Land Rover Centre Diff Lock

The diff lock (as used in coil sprung Land Rovers ) functions as follows.

This unit is a centre diff lock, which means that it operates BETWEEN axles. This is opposed to diff locks that operate on the individual front and rear axles and can be retro fitted to Land Rover Differentials.

A permanent 4x4 vehicle (Coil sprung Land Rover i.e. Defender Rover/RR) supplies driving torque to both axles equally in hard surfaces. Due to the differing route followed by the front and rear axles during a corner, the system uses a centre differential. This centre diff prevents "wind-up" on hard surfaces i.e. it lets the axles turn at differing speed.

When you get into a situation where less traction is available or one wheel (any wheel) is in the air the vehicle will loose traction entirely and stop moving. All power is "escaping" from the airborne wheel, this is the centre diff doing it's job as per normal operation.

In order to get past this, a centre diff lock has been designed in to the diff: When the centre diff is locked the diff effectively no longer exists i.e. the front and rear axles are locked together and driving power is now sent equally and unconditionally to BOTH axles.
The net effect of the centre diff being locked is that power is available to both axles and as such, at least one wheel on each axle must spin for the vehicle to loose traction.

Vehicles with selectable 2x4 and 4x4 like Leaf sprung Land Rovers, do not have a centre diff lock because the do not have a centre diff at all. When the vehicle is in 2wd only the rear axle is driven while the front is disabled. When 4wd is engaged, the front and rear axles are locked together and power is again sent equally and unconditionally to both axles, therefore you can see that a Defender or Range Rover with centre diff locked is identical to a Leaf Sprung Land Rover on 4wd.

So, where do I lock the centre diff and where do I unlock it ?

If you are going off tar where there is a possibility of loosing traction, engage the centre diff lock. i.e. Up and down hills, mud, ice, snow, uneven surfaces.

Do not use any diff lock on tarred / concrete surfaces or any similar high traction surface, the difference in front to rear axle speeds will cause extreme torque build-up in the transmission to such an extent that transmission components will wear excessively and/or snap. This build-up is called "wind-up", Even a little hard surface driving in diff lock will cause the diff lock to not dis-engage due to transmission tension


KAM Diff Locker

The KAM Diff Lock is electrically controlled via a heavy duty solenoid located inside the diff pan. A cable runs from the solenoid to the an illuminated rocker switch in the cab that engages the diff lock. The solenoid itself is a dual coil type, electronically controlled and protected by an integral solid state commander module.

A short 45 amp burst of power activates the solenoid which then preloads a spring. The spring then forces the sliding dog along a newly patented locking tube witch locks the sliding dog on to the carrier. The diff locker is now engaged and give continues drive to both wheels. A constant 0.5 amp draw holds the solenoid in a locked state. This new tube design means that you can use your original shaft or shaft that have been purchased previously. If you do bead a shaft then the diff locker will still work

We have improved the KAM diff locker system so that you can now add LSD Shaft CV,s and Crown wheel and pinion in stages to the base diff locker unit depending on your off road and competition requirements. You can use your standard or existing shafts or up grade to KAM proven range of parts. Lock up time of is 0.4 seconds. until the driver switches it off 100% Lock to the axle Doubles your Traction off Road Heavy Duty 4 Pin Carrier Use Any 24 Spline Half Shaft 8mm Aluminium Diff Guard as std Add LSD to locker Solenoid Activated 12v or 24v


KAM diff locks in a Defender 90 Td5
KAM Diff Lockers from LandyOnline


Detroit TruTrack Torque Biasing Diffs

I've got trutrac (torsen) torque biasing diffs front and rear on my 2 Door Range Rover.

The reasons for this are that I kept smashing normal diff centers, and that I got good prices on the trutracs as opposed to ARBs or anything else.

I fitted one to the front first, and then to the rear.  I avoided an auto locker at the rear as I was [it would seem unjustifiably] worried about the self locking thing.

A few opinions from me;

On a permanent 4WD vehicle, a trutrac on the front *does* very definitely and for the worse affect the handling of the vehicle on tarmac.  You get torque steer dependent on the amount of gas you give it and the degree of turn on the wheel, and the direction of torque steer reverses if you reverse the power flow through the transmission.  The front tyres must be close on identically worn in order to prevent pulling.  The suspension bushes must be in excellent condition.  The effect is very annoying but you get used to it.

The trutrac on the rear is undetectable in on-road driving. When the thing engages or disengages is not an issue as it is permanently engaged...  it is the degree of engagement that makes a difference, and it behaves very predictably.  No nasty habits.

I used to occasionally spin a wheel when pulling away around corners on wet tar, and be able to get wheel spin at the lights if I was really going for it.  I can't do that any more, and I have really been trying (for testing purposes of course...).

Stability and drive on dirt roads is much better than with open diffs.  Less tendency to drift and almost as stable with the centre diff unlocked as with the centre diff locked [dirt road aficionados with Range Rovers should understand what I mean].  With centre diff locked it is incredibly stable when compared to an open diff vehicle.

Tight corners taken at speed under power are a joy, and the tendency for the front end to wander if the corner is corrugated is reduced.  I fully understand why rally drivers prefer these.

Off the road it is still fun to be able to get stuck with one wheel of each axle in the air.  If you don't get a wheel off the ground, it is *very* difficult to get just one wheel of an axle spinning.  This is particularly noticeable when ascending loose slopes; other vehicles get halfway up, sit and spin opposite wheels.  Rangie climbs the slope with all 4 wheels scrabbling.  Descending slopes is also more pleasurable - I've often experienced a few meters of mad slide when descending under engine braking alone and losing traction on a front and rear wheel, easily mopped up with the brakes, but it doesn't try to break away in the first place with the trutracs installed.

The torque biasing on a trutrac appears far greater in reverse than forward.  This is why the fronts and rears are not interchangeable, and why my car likes to reverse out of obstacles even when it looks totally hopeless.

You can pull the vehicle through an obstacle with only one wheel on the ground by using compensation braking. Maybe that should be compensation breaking.  I'm up to 4 half shafts and 2 cv joints, broken, due to operator error.  You can stand on the brakes and give it lots of foot in 1st or reverse low range but something is going to break.  Namely half shafts and CV joints.  The trutracs will put the torque where it is needed but only until something self destructs.  Those CV joints are very, very strong.

Trutracs are *not* diff locks.  I haven't managed to break any transmission bits when not using the brakes yet.

Following on from that, I can testify that trutracs are very strong things.  I've sat spinning wheels and generally giving them abuse that would have finished off a normal diff in short order.  I've had them out a few times (replacing half shafts...) and there is no sign of wear, metal pieces or anything else.  I would reckon on shearing
the pinion off before breaking one.

The best bit.  Sand.  This is where they really perform.  It's not a lock, so it doesn't affect your directional abilities, but it gives all four wheels power most of the time whilst allowing them to find their own speed.  It doesn't mean you can go up dunes any easier, but it makes the whole experience a lot more controlled and there aren't usually any rooster-tails as you get stuck - all 4 wheels just dig and go down like a diff locked vehicle.  The effect is so good that you don't really notice anything, but you get a sense of how much more easily everything seems to be happening.

- Andy Grafton


ARB Air Locker

ARB Air Locker functions with a button on the dash.

The system is powered by a pump which has a small air tank and a pressure switch. You can "enable the
system" by fitting a switch in the main power line to the pump, when you go off-road, you can switch it on, the pump will run for a short while and charge the tank. The pressure switch will keep the tank full.

When you hit the button, a solenoid opens and sends the air charge to the diff housing which contains the main locking mechanism, locking the diff instantly.
When you hit the button again it releases the solenoid and the pressure line to the diff is discharged to the atmosphere.
I find the ARB's great. The front one can create some interesting moments and makes your steering wheel useless if on a hard surface.
Note that a "hard surface" is in fact a steep hill with serious holes in where you must go straight up, you must dis engage the front locker before reaching the top if you want to turn the moment you reach the top.

Like they say :"Jy ry jouself bang met 'n ARB locker"
You can get yourself into such deep ^*#^% it is unbelievable...

-Brian Cotton


LandyOnline KAM Diff Lockers

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