Morris Minor Owners Club

Well done.

I'm about to swap a 4.22:1 diff for a 3.9, as well. I've no idea whether the oil seal is good or not, but assuming I have to change it, and I use a new crush washer.....what if I reach the 11-13 in-lb setting before the nut is torqued to 140 ft-lb?

Watch the video on page 1 right to the end, they explain the crush washer and how to torque it up. The 140 ft/lbs is an ish but the 11-13 in/lbs are more important. I know that its 45 mins long but its worth it.

Ok, here is my home made in-lb torque tester:-
It's a bit Heath Robinson, but it should do. It's a piece of aluminium angle, with two holes drilled for the diff flange bolts. I have measured 12" from the diff centre of rotation, and a 1lb (or 454g if you prefer to use sensible units) weight will sit on the angle at that point.
Testing it on my spare 3.9:1 diff shows that the pre-load is way too low, as it rotates under the weight of the angle alone! So is it worth replacing the crush washer, and getting the pre-approval load right?
The video below shows that there is about 1/8" backlash in the diff at the flange edge.

https://youtu.be/ZFAzgzuIpD8

Cheers N

The crush washer is located between the two pinion bearings and there is no reason to touch it or replace it when replacing the pinion seal.

To replace a crush washer you have to completely strip the diff for access to the crush washer.

Just remove the pinion flange replace the seal and refit the pinion flange and tighten to 140lbf ft.

If it has been already tightened to 140lbf ft it will not impact on the crush washer (if fitted).

Before removing the pinion flange feel what the resistance to turning of the flange is. Of course the scientific way is to hang a weight on the end of a foot bar bolted to the pinion flange (one foot length from the centre of the pinion shaft) and see what the resistance to turning is.
Your aim should be to replicate the turning resistance (before undoing the pinion nut) when torqueing the pinion nut but not exceeding the 140lbf ft.
Setting the pinion nut to 140lbf ft may improve the turning resistance of the pinion. The pinion resistance to turning/preload should really be done with the crown wheel removed or you will get a false reading as you are not only trying to turn the pinion but also the crown wheel.
If a crush washer is fitted it is a matter of balancing the two factors i.e. torque of the pinion nut against the pinion preload.

So.... Is the crush washer not automatically fitted?
What about the pre-load? The pinion moves under the weight of the angle alone-doesn't that mean the pre-load is too low?

No - it cannot be assumed that a crush washer is fitted it may be a solid spacer.
The pre-load does indeed appear to be low but unless you are prepared to dismantle the diff and fit a new crush washer I would just torque the pinion nut to 140lbf ft and see where you are with the preload.

Ok. Is there no way of telling without dismantling? And should I still test the pre-load as i torque it up, to make sure it doesn't exceed the current pre-load?

There is no clear way of telling as to whether you have a crush or solid spacer without dismantling.

A crush spacer would if you continue to tighten the pinion nut compress beyond the correct preload but if that happens the diff needs to be dismantled and a new crush spacer fitted. You can go up to the preload but once past it you have to start again with a new crush spacer

Yes - balance the torque loading against the preload but do not exceed the 140lbf ft.

Ok thanks. I was under the impression that you have to reset the pre-load when replacing the oil seal.

Do you have to reset the pre-load when replacing the differential bearings? Do you have to go through all the procedure detailed in the BMC workshop manual, involving the dual test indicator?

Cheers N

It is not always necessary to reset the pinion bearing preload when replacing the pinion seal.

If you replace the pinion bearings you have to go through the whole procedure as outlined in the BMC wksp manual.

If you try to short cut the process you will in all probability end up with a very noisy diff.

OK, I’ve now watched the video on p1 all the way through. I have a couple more questions 

1-If a solid spacer is fitted, instead of a crush washer, does the flange nut still need torqueing to 140lbft? Does the pre-load still need to be measured?

2-What if the pre-load is reached when the torque is below 140, say 110 or 115lbft? Is that ok?

3-From reading the BMC workshop manual, AIUI, the diff cage & crown wheel can be removed, cleaned and pinions etc replaced, as long as the bearings are not changed, and everything goes back in the exact same order as it was assembled. Is this right?

My replacement diff is full of crud, and I’d like to give it a clean. I also think there’s a little too much play in the diff pinions, as there was in the video, so I may replace them if necessary.

Cheers N

1.

If a solid spacer is fitted you can torque to 140lbf ft. The factory applied preload should not be effected. If you have worn pinion bearings the preload may then be not factory spec. You have to take your chance and see what happens.

2.

What is required depends upon the amount of reduced torque to attain the correct preload. Just try the torque setting specified and see what happens.

3.

The diff crown wheel and bearings can be removed and refitted without upsetting the crown wheel to pinion settings. The sun and planet (diff pinions) gears can be removed and replace but follow the manual instructions and settings closely.

Thanks Phil. The manual kind of explains, but leaves tantalising gaps in knowledge!

As I'm now going to overhaul my 3.9:1 diff and fit it in place of the 4.22:1, I'm going to start a new thread covering the process, rather than clog this one up.
Cheers N

Declan_Burns wrote: ↑Fri Feb 22, 2019 11:16 am I did like their idea to use the shims on the outside of the carrier rather than between the bearings and the carrier.

Has anyone found these shims in the UK?

I'm sure they'd post them.

ndevans wrote: ↑Tue Sep 17, 2019 10:05 am I'm sure they'd post them.

Oh they will, but I'd rather support a UK seller if possible. Once I know the dims it wouldn't be too difficult to source something I guess.

I guess the inside dimension is the inner race dia, and the outside is the outer race dia + something. It's the something that isn't known, but it could presumably be deduced somehow.

ndevans wrote: ↑Tue Sep 17, 2019 3:09 pm I guess the inside dimension is the inner race discuss, and the outside is the outer race dia + something. It's the something that isn't known, but it could presumably be deduced somehow.

It’s just a matter of measuring the bearing. If I had one I’d do it. I better order a couple