Offroad-Express

been offerd lsd out of a terrano for me safari 1991 grandroad lwb. wondering how to sort out if it is compatible b4 stripping me frond diff , as need to keep it on the road at pressent any help greatly appreciated

Pull an axle out of the Terran and count the inner axle splines.

Or if its already out of the vehicle, check that:

Crown Wheel Diameter: 255mm

Crown Wheel to Carrier : 9 bolts

Axle splines: 31

Crown wheel Teeth: 37

Pinion Teeth: 9

If all that matches up on the Terrano diff, then it will/should go in.

If memory serves me correct then I think you may be wasting your time. I thought only the mq/mk patrols were compatible with terranos.
Al

Should be able to fit a Terrano LSD, as long as you get the right one. There are a lot of guys in oz starting to do this, although there is still a lot of debate as to whether or not its a good idea.


Dave

Well, i don't see why it would be a bad idea. Its that personal preference thing again. Oh, and the fact that they pay big $$$$ for the diff head in question, so the $$$ becomes comparible to that of an auto locker, and the auto locker gives you more traction at the end of the day.

Over here thats not an issue, second hand diffs from terranos are every where.

If its a WD21 Terrano or Navara, then the diff will go in. Its an R50 or anything else, it won't fit.

The reason why we know this works is that the same auto locker fits both the front of a GQ and the open rear of a Terrano. Therefore they are the same diff head. If the Terrano had an LSD in the rear instead of the open diff, then that LSD would fit the front of the GQ.

I read somewhere that the reason they are unsure if it is a good idea or not it there unpredictability as it can come on when you dont want it to and all of a sudden you loose your steering or it throws you in a direction you dont want to go, but that would be no different than an auto locker.
This is the main reason it puts me off ruinning an auto locker in the front of mine.

But unless you do alot of high range 4wd stuff, it doesn't seem to be a problem i have found.

DieselBoy wrote:But unless you do alot of high range 4wd stuff, it doesn't seem to be a problem i have found.

Good to know, have you got your working properly now?

The unpredicitibilty of an LSD up front could also take a toll on your CV's, reversing up hills, wheels turned, LSD tightens, bang there goes your CV but if you drive to suit that set up and know about it then it shouldnt be a problem.

doddzee wrote:

DieselBoy wrote:But unless you do alot of high range 4wd stuff, it doesn't seem to be a problem i have found.

Good to know, have you got your working properly now?

The unpredicitibilty of an LSD up front could also take a toll on your CV's, reversing up hills, wheels turned, LSD tightens, bang there goes your CV but if you drive to suit that set up and know about it then it shouldnt be a problem.

Urrrrm, not treading on your toes doddzee, but how does that last comment work??



Clutch-Type Limited Slip
The clutch-type LSD is probably the most common version of the limited slip differential.

This type of LSD has all of the same components as an open differential, but it adds a spring pack and a set of clutches.

If one wheel wants to spin faster than the other, it must first overpower the clutch. The stiffness of the springs combined with the friction of the clutch determine how much torque it takes to overpower it.

In a situation in which one drive wheel is on the ice and the other one has good traction: With this limited slip differential, even though the wheel on the ice is not able to transmit much torque to the ground, the other wheel will still get the torque it needs to move. The torque supplied to the wheel not on the ice is equal to the amount of torque it takes to overpower the clutches. The result is that you can move forward, although still not with the full power of your.

Lsd's can be set up to have a high preload, but they will still allow one wheel to spin freely in the right situation.

Basically, an LSD is always working, it does not lock up, in fact its quite the opposite. The clutch pack will slip and alow one wheel to stop and the other to spin way way way before the torque would blow a CV.

I dont know alot about LSD's so i may have just made a comment that was wrong

DieselBoy wrote:When a situation arises, say you are crosing a rut and one of the wheels comes off the ground, the preload in the clutch pack is not enough to drive that wheel which is still on the ground, so it spins the wheel that is in the air as it would with an open diff.

So if this is the case then putting an LSD in seems to be a waste of time as this is where you need traction the most. But that suituation i commented on would apply to an Auto locker.

Yeah, but the LSD is still providing a small amount of torque to the wheel in contact with the ground and some times its enough. Depends on how tight the clutch pack is.

As for the auto locker. Well, almost........

An auto locker opperates similar to an LSD in some ways, in that it is always locked providing drive to both wheels at all times.

It only ever alows the wheels to rotate in dependantly of one another when cornering on a hard surface.

The wheels are always locked together, and then when you come to turn a corner, it allows the out side wheel to rotate faster than the inside wheel.

It never allows one wheel to spin slower than the other.

So in your scenario of reversing up a slippery hill, the locker will be locked the whole time regardless of whether you have full lock on or not. If you were reversing up a hill with good traction, it would alow the out side wheel to over run the inside wheel, but as you had good traction, there would be no wheel spin so no sudden locking.

To unlock, the locker needs the out side wheel to be driven faster than the inside wheel by the ground. If the ground is slippery, then the outside wheel will not be driven with enough torque to make the locker dissengage.

So no sudden locking under load unless the lockers knackered

what i find hard to understand is how it doesnt unlock when you have one wheel off the ground but does if you are going round a corner on hard ground. i thought that when there was little torque appiled to them they would ratchet and would lock up when there is torque applied??
can any1 explain?

cheers Pete

Heheh, this is going way of topic, but may help nuts figure out if a LSD is what he really wants


This is getting bloody tricky to explain. Much easier with a locker unit and a diff head sitting in front of you

The locker consists of two halves.

Each half consists or a side gear and a coupler which go together to form a dog clutch. Spring loaded pins are incorporated to allow the dog clutch to release and ratchet.

The two halves of the locker replace the side gears and spider gears.

The shaft the spider gears worked on goes between the two halves of the locker.

With the locker in the carrier, and the shaft through the locker, and drive was to be applied to the crown wheel the whole assembly would rotate in the same direction.

When the diff and locker is in the vehicle, its easier to think of the axle shaft and the half of the locker on that axle's side as being one unit, and the same on the other side. The drive to the axles through the locker is provided by the pin which is fixed to the carrier and separates the two halves of the locker.

There is a specific amount of play in the fit between the halves of the locker and the pin fixed in the carrier. This is to allow clearance for the locker to operate correctly.

The recess in the halves of the locker are shaped so that the pin through the carrier goes very very slightly over centre when drive is applied to the carrier.

So what happens, is that when drive is transmitted to the crown wheel, the crown wheel and carrier (remember the pin is fixed in the carrier) rotate, which takes up the play between the halves of the locker, forcing the dog clutches in each half of the locker, to lock tightly together, providing drive to the wheels on both sides.

To anytime the carrier is being driven by the crownwheel and pinion, the locker is locked up. (confused??)

When you corner, the wheel on the outside is driven by the road, faster than the whole assembly in the carrier. The half of the locker on that side is driven by the road into the position where it is aligned with the pin in the carrier again and the load holding the dog clutch tightly together is released. (remember the dog clutch was locked together by the driven carrier pin forcing the two halves of the locker apart due to the shaped recess in the locker)

When the load is released on the dog clutch, the wheel on that side (the outside wheel of a corner) it is allowed to turn faster than the inside wheel. This results in the ratcheting sound.

As the vehicle straightens up, the out side wheel stops being driven by the road faster than the carrier assembly and that half of the locker starts to be driven by the carrier pin again, causing the pin to ride up and go over centre again and lock the Dog Clutch together again tightly.

If no drive was being applied to the crownwheel and carrier, the halves of the locker would not be locked together as the carrier pin is not being driver to seperate them. You would be able to spin 1 wheel by hand.

As soon as drive is applied the pin goes over center again and the dog clutches on the two halves of the locker are locked tightly together again.

You gotta have one in front of you to see what I'm talking about!!!!!!!!!!

thanks that prittymuch makes sense. what happend under engine breaking? seems the ground is turning the wheels? ir going down a hill? my assumption is still locked as there would be pressure from the engine sitll just like when going in reverse?

Cheers pete

Yep, forgot to put that in.

Engine braking, where both wheels are being driven by the road makes the locker inside the carrier try to go faster than the carrier and locks its self up on the carrier pin again, forcing the dog clutches to lock together tightly.

Basically everything hinges around that carrier pin and the forces opperating on it, depending on what is driving and being driven.

Its such a super simple system, but so hard to describe!!!!!!

With an auto locker none of the wheels can go slower than the drive.

That is, one wheel can be at drive speed but the other wheel must be at drive speed or faster.

When cornering, you normally think that the inside wheel goes slower than the outside wheel which it does but it's the same speed as the drive though.

With an auto locker the inside wheel remains at driven speed but the outside wheel is permitted to go faster than the inside wheel. It cannot go slower.

This is how traction is maintained, both wheels must be moving at the same or greater speed than drive. The allowance for a wheel to go faster permits turning etc.

There is an affect on steering but I don't think it's big. Those with auto lockers here will no doubt post their thoughts.

Matt.

thanx for all the input guys ... .... sounds like its worth a shot so will have to find out if its the right lsd to match me front diff b4 i go any further will let ya know how i get on thanx heaps