Rear diff - checking lsd function.

[wobbly]

I noticed today that with one wheel in the air, other on the ground, and the handbrake off/ gearbox in N, the wheel in the air will not rotate.

If the truck had an open diff the I would expect the wheel to spin, my 95 has a lsd so is this a sign that the lsd is working?

I've read that the lsd is good for 50,000miles, but the truck is on 100,000.

How else can I check it?

Pete

 

[J66P]

do a similiar excercise but jack the rear wheels up and do the same, if in good order they will both turn the same way and you wont be able to hold one without the other turning

 

[wobbly]

Its the spinning in the same direction is the key I guess.

Cheers

Pete

 

[ModelMakerMan]

Another test is to jack one wheel up and try to drive off the jack. If the wheel in the air just spins the LSD is fubar.

 

[BobMurphy]

I don't have a Limited-Slip Differential (LSD), but from the little I know I would have thought that it will only work when the difference in rotational speed of the wheels exceeds some reasonably-high threshold.

Otherwise, how does the car corner without scrubbing the tyres ??

I would have thought that it should be possible to turn one wheel by hand while the other was on the ground (providing the transmission is in neutral and the propshaft can turn).

The centre diff in the transfer box has to be open too, or it will be trying to turn the front wheels - is the Transfer lever in 'H' ??

What you have doesn't sound right to me (but I have no experience of these things ).

Bob.

 

[J66P]

afraid not the higher the torque the better the grab basically, cornering isnt an issue because its low torque, if you were to nail it into a bend then it would try and lock up, on the jack it will grab sufficent for you to tell if its working at all. I have had plenty to do with them being previously a Jeep owner with an LSD fitted that are renowned for wearing out

 

[BobMurphy]

afraid not the higher the torque the better the grab basically, cornering isnt an issue because its low torque, if you were to nail it into a bend then it would try and lock up, on the jack it will grab sufficent for you to tell if its working at all.

Interesting . . Thanks for that. I'll have to look for an exploded diagram as I'm curious as to how it works now .

Bob.

 

[J66P]

basically a wet clutch

 

[Roger Fairclough]

The wear on a LSD is similar to your brakes. The more you use them-----. Consequently, if you drive lots of straight (relatively) roads, such as M/ways, the LSD discs don't rotate as much, and don't wear out as fast. If you live in Milton Keynes, with all it's roundabouts---I think that's the place---your LSD will wear out faster. Generally, after 50,000 miles it's past it's sell by date and after 100,000 miles it's FUBAR.

The LSD works by restricting the ability of the diff. to spin out. A normal diff. takes the line of least resistance. By lifting a wheel, you stop it's grip on the ground and all the power to that axle is directed to that wheel. The wheel still on the ground is deprived of any power and the axle is dead. A cross axle situation will see both axles dead and you cease to move. The LSD can partly control this spin out by applying an amount of grip to reduce it. The problem is this grip is related to the spring pressure on the LSD plates. The more pressure, the greater the grip but this also means that in normal bend turning, you can provoke stability problems as the LSD doesn't want to allow the wheels to turn at the different speeds necessary to turn.

Once the LSD is FUBAR, the cost of repairing it is just to high to warrant it. You would be better off to fit a Detroit Trutrac.

Roger

 

[wobbly]

I am going to order some new garage equipment from Machine Mart tomorrow, should be delivered Wedenesday, so I can do the job (again) on Thursday, can check wheel rotation etc when the whole back end is up safely.

I didnt alter the centre diff, so its in H4 as per normal on road use.

Roger - the tru-trac.....is that a replacement lsd, or is it a locking diff with switch, air line etc.

Cheers

Pete

 

[Cptsideways]

I'm assuming these are the regular Toyota clutch pack type? in which case they do not do much even when new, max torque they offer is about 75ftlb to nil if well used. If you want it to work repack the clutch packs with some extra plates & or shim it. 100+ ftlb is then possible.

 

[Roger Fairclough]

I am going to order some new garage equipment from Machine Mart tomorrow, should be delivered Wedenesday, so I can do the job (again) on Thursday, can check wheel rotation etc when the whole back end is up safely.

I didnt alter the centre diff, so its in H4 as per normal on road use.

Roger - the tru-trac.....is that a replacement lsd, or is it a locking diff with switch, air line etc.

Cheers

Pete

Pete

Machine Mart are expensive. Before you order anything from them, let us know what you are after, and what you think you need them for.

The Trutrac is a self contained semi locking diff. No wires, air or bowden cable and no specific LSD oil. In normal road work it is benign and quiet. It comes into it's own with it's ability to control the back end. Normal hard cornering, especially with mud tyres on a wet road, that would normally result in the inner, less loaded wheel, breaking away is easily controlled. Hard use wont wear it out. Off-road the diff. can transmit 75-80% of available power. In use it is subtle and it is only later you realise how good it is.

The unit replaces the standard Toyota LSD.

Roger

 

[Roger Fairclough]

I'm assuming these are the regular Toyota clutch pack type? in which case they do not do much even when new, max torque they offer is about 75ftlb to nil if well used. If you want it to work repack the clutch packs with some extra plates & or shim it. 100+ ftlb is then possible.

The more you shim an LSD diff. the more violent the operation will be. It will attempt to grip beyond it's normal limits and will then "let-go" quickly. This can create wayward handling charateristics. Plus there's the problem of not knowing how much to shim it by.

Roger

 

[Cptsideways]

I'm assuming these are the regular Toyota clutch pack type? in which case they do not do much even when new, max torque they offer is about 75ftlb to nil if well used. If you want it to work repack the clutch packs with some extra plates & or shim it. 100+ ftlb is then possible.

The more you shim an LSD diff. the more violent the operation will be. It will attempt to grip beyond it's normal limits and will then "let-go" quickly. This can create wayward handling charateristics. Plus there's the problem of not knowing how much to shim it by.

Roger

They are easy enough to shim up & test with a torque wrench & 100ftlb's you would hardly if ever notice on the road.

 

[Roger Fairclough]

Sorry Captain, but if you are trying to go from 75 to 100lbs/ft, I don't see the real advantage.

Roger

 

[BobMurphy]

Roger - the tru-trac.....is that a replacement lsd, or is it a locking diff with switch, air line etc.

If you can find a quiet corner (and an ice pack for your head) have a look here:

http://en.wikipedia.org/wiki/Limited-slip_differential

It mentions the Truetrac, which is a "Geared, torque-sensitive mechanical limited-slip differential" .

Eaton Detroit make the 'truetrac' - which is an LSD, and the 'locker' which is a full-on auto-locking diff locker (don't use it in the front ).

As ever . . Its a whole new can of worms .

Bob.

 

[wobbly]

Am going to see if I can raise the back end high enough with my existing jack/stands to get the tyres back on, see what happenns when I spin the wheel, would be surprised at 100,000 miles that it is working though.

Cheers

Pete

 

[wobbly]

Machine Mart are expensive. Before you order anything from them, let us know what you are after, and what you think you need them for.


Hi roger,

I've posted the list on the diy servicing section.

Cheers

Pete