Differential Preload

[JackIIA]

I'd appreciate some feedback on preload on a Rover type differentials. Mainly, how much preload is about right.

My assumption has been that you should be able to spin the pumpkin and it would turn at least 3 times or so on it's own for proper preload.

I've got two different diffs, both of which won't spin at ALL on their own. When I installed one in the truck, I could only turn the front wheels with a large screwdriver between the lugs. The fact that my newly sourced diff has the same situation, led me to question if this is a rover thing. I doubt it, but thought I'd throw it out there.

Also, anyone know the correct preload by the book? I didn't see it in the manual. Just said to use a scale and measure.

[KevinNY]

Pinion preload has to be measured on the bench, not by spinning a wheel. A bunch of other factors are involved in spinning a wheel, least of which is pinion pre load.

[JackIIA]

Pinion preload has to be measured on the bench, not by spinning a wheel. A bunch of other factors are involved in spinning a wheel, least of which is pinion pre load.


That may well be, but as a sanity check, you SHOULD be able to spin the carrier and get a sense of whether you've got the wrong shimming in there. Maybe not with exactness, but with some general sense.

This thing doesn't 'coast' on it's own after pulling your hand away. Nada. That's the second one I've pulled that is like that (not worked on by me).

It simply doesn't sound right to me, and I can't see it being different from cars, but perhaps that is the case. (?)

[bkreutz]

One of the quick checks I've used over the 40 years I was a mechanic was to pull the axles and propshaft, then I want about 15 inch pounds at the pinion nut. Trying to tell with the axles, driveshaft, wheels, brakes, and all the other things in place is putting too many variables into the mix (as was mentioned)

[I Leak Oil]

JackIIa, the method you're using really isn't any indicator of proper diff setup. Not on a rover or any other vehicle. As has been mentioned a couple times now there's just too many other vehicle systems that contribute to how much the wheel spins. The way to setup and check the preloads are in the book.

If your wheel isn't spinning on it's own then it's most likely a combination of the drag from the wheel bearings, brakes, diff., axle u-joints. It really has nothing to do with checking diff bearing preloads though.

[JackIIA]

My bad for not being clear. Neither diff is IN the vehicle. I pulled the first after the issues with difficulty turning the front wheels - to confirm where the problem lay. So there is no drag apart from the bearings and shims of the diff itself.

The 15 inch lb pound suggestion is a good one, thanks. ILO - the write up for differential rebuilding in the manual leaves a lot to be desired, at least for me. I've reviewed Yukon's pamphlet - much better, but of course, it's not written for these differentials. I'd much rather just drop in a good used one rather than rebuild it.

[KevinNY]

Ok that clears it up. As far as I've seen with diffs, they WON'T freewheel. They would be way to loose if they did.

[Donnie]

I'd appreciate some feedback on preload on a Rover type differentials. Mainly, how much preload is about right.

My assumption has been that you should be able to spin the pumpkin and it would turn at least 3 times or so on it's own for proper preload.

I've got two different diffs, both of which won't spin at ALL on their own. When I installed one in the truck, I could only turn the front wheels with a large screwdriver between the lugs. The fact that my newly sourced diff has the same situation, led me to question if this is a rover thing. I doubt it, but thought I'd throw it out there.

Also, anyone know the correct preload by the book? I didn't see it in the manual. Just said to use a scale and measure.
Jack, there are several factor's to consider when setting up a rear; there is carrier brng. preload, pinion bearing preload, back lash, that is the clearance between the ring & pinion, heel & toe, that is the contact area where the 2 gears mesh---------carrier moves sideways & the pinion moves fore & aft to alter these adjustments, you can have correct brng. preload, but be off on your contact. this will cause the rear to sing either on the pull or on the coast. either red lead or prussion blue is needed for this set up. The pinion brng preload that was mentioned before is ok, just wanting to let U know that there is a lot more to be concerned with for a good job..........donnie

[I Leak Oil]

Ok that clears it up. As far as I've seen with diffs, they WON'T freewheel. They would be way to loose if they did.

That's correct, they will not freewheel.
So, taking a step back...check it on the bench and re-evalute it. Perhaps there's nothing wrong with either diff. Hopfully....

[JackIIA]

Absolutely. I will give it a check with gear marker. I wouldn't have even thought about the issue with 'no spin' had it not been for the fact that when fully assembled, the front drums were a bear to turn and the rear were spinning just fine.

If the gear pattern turns out OK, does that mean it couldn't be the differential (assuming I don't hear alot of bearing noise)?

Will report back. Donnie - your comments highlight why I don't want to work on it!

Thanks guys.