Pinion oil seal

[Baldwin]

My local garage did an MOT on my car and suggested the pinion oil seal be replaced. It's true that the car does mark its territory beneath the axel/prop shaft, but how serious does it have to be before it's changed? How good are modern remanufactured seals? Any recommendations for suppliers. The garage owner is an older mechanic and has a small number of customers with classics.

[mowogg]

They harden with age and stop being effective. I would get it replaced

[les]

We all have different ideas of what is serious. Depending on how much of an oil leak you can tolerate, will determine when to replace things.

[svenedin]

The only way you can tell if it's "serious" is to have some idea of how much the seal is leaking. You would have to note the mileage and then check how much oil its takes to top the diff back up. It's a common place for a leak. I allowed mine to leak for a while but then I got ESM to change it. Actually I watched them do it and good grief there's a lot of torque needed to do the job. I was glad I decided against trying to do it myself. Seals are readily available from the usual suppliers. Sometimes a Speedi-sleeve is also needed.

Stephen

[myoldjalopy]

Yes, Stephen is correct. Check the rate of oil loss. You don't want to have to be topping up the oil frequently. That's a bore. And if the diff starts to run low on oil it will become increasingly noisy, and if too much is lost damage will occur....

[oliver90owner]

First of all, check that the axle breather is clear - oil will pass a seal as the casing warms and if the pressure in the casing becomes positive.

Sometimes a fresh seal line on the shaft can be ‘arranged’, avoiding the cost of a speedi-sleeve.

The cost of oil top-ups can soon exceed the cost of a simple oil seal.

[Andmurph]

Stephen is right about the torque required to undo the pinion nut. I changed the seal on the pickup last April and had to make a tool to hold the flange still whilst using a breaker bar in a four foot cut down scaffold pole to turn the nut. All most unpleasant with the car on stands. From memory the new seal was a couple of pounds from ESM and has worked well so far.

[svenedin]

Here's the seal: https://www.morrisminorspares.com/rear- ... 71-p831254

This is the sleeve: https://www.morrisminorspares.com/rear- ... r-p1238342

My car didn't need the sleeve for this but it has needed a sleeve for the rear wheel hub oil seal on one side due to axle wear on the seal running surface.

Definitely check the axle breather as Oliver suggested. Also make sure the leak really is coming from the pinion oil seal. My diff has a tendency to leak from the drain plug (fixed by wrapping the thread with plumber's PTFE tape).

Stephen

[philthehill]

The above comments appear to make replacing the pinion seal easy but it is not that straightforward.
If you have a collapsible spacer fitted between the pinion bearings and you end up compressing the spacer further you could end up over pre-loading the bearings which will lead to their failure.
If you have a solid spacer between the pinion bearings then there are no worries but you will not know what spacer you have unless you strip out the pinion.
My advice is - if you are not confident or sure what to do get someone (i.e. the garage owner mentioned above) who is experienced in the job to replace the seal.
Phil

[mike1864]

I keep a tray under the diff to monitor any leaks. Does this make sense?
When I upgraded my SII to a modern power train (50 years ago!), I discovered that the new diffs don't have a filler hole in the side. Instead I was supposed to use the filler hole in the axle housing; which of course the SII's rear axle didn't have. So I have to fill via the top vent hole. Level checking can only be done by draining, measuring and re-filling.

[MMT1968]

I read in the workshop manual that the nut at the diffs entrance flange must be torqued to 140 ft lbs. Is that correct? Seems quite a lot to me.

Chris

[svenedin]

I read in the workshop manual that the nut at the diffs entrance flange must be torqued to 140 ft lbs. Is that correct? Seems quite a lot to me.

Chris

Yes it is a lot and that is why it is difficult to do at home which is why I left this job to a Minor specialist garage.

Stephen

[MMT1968]

140 ft lbs means 190Nm, puh! I thought about torqueing the nut to 125 ft lbs first and see how the diff does. If not good I can torque it a bit more to 140 ft lbs. In that case I can safe the crush spacer on the first hand and do not need to dismantle the diff again to install a new crush spacer.

Chris

[philthehill]

If you do the pinion nut to less than 140 ft lbs then the pinion bearings can more easily be forced apart leading to a noisy diff. When the pinion turns the crown wheel the pinion is pushed away from the crown wheel so opening up the distance between the two taper bearings. The pinion nut is tightened to the 140 ft lbs to eliminate any possible increase in distance between the bearings which leads to a loss of bearing pre-load.

[MMT1968]

Phil,

Thanks for that description. I will torque the nut to 140 ft lbs and follow your recomendation and hope it works.

Chris

[don58van]

Hi Chris

Please let us know how you did it and how it went. I have the same job coming up soon and I am sure others will too.

Don

[Michiel]

IMG_20200515_110642.jpg (989.84 KiB) Viewed 43021 times

Photo is upside down. No idea why . One way to loosen the pinion nut. The bar bolted to the flange is a tie bar but I saw also a piece of angle bar with a hole drilled in it being used. The end of the pipe rests on top of the leaf spring. Use a pipe on your T-bar also. It is not as tight as you should think.

[MMT1968]

My nut was about to come loose with a little more power than I could provide with my fingers. That was the sign for damaged bearings. To tighten it I made a pair of angeled steel drilled to measure and bolted to the workbench. That worked well enough.

Chris

[MMT1968]

@Don,

As you asked for an Update:

Differential refurbished, follow up.

After removing the diff from the axle I removed the nut at the entrance flange first. That was easy as I had bolted two pieces of angeled steel to the flange and clamped these to the workbench. The flange, nut and pinion shaft were marked first. The nut came off easily. Then the pinion shaft was removed and the inner rings of the inner and outer bearing were knocked out with a punch.
After cleaning all surfaces in the differential casing the new outer parts of the inner and outer pinion bearing were pressed in. The inner part of the inner pinion bearing was pulled off with a bearing puller without problems. The new part was heated on a small cooking plate and slided smooth and perfect in place on the pinion shaft.
The two ball bearings holding the differential cage were pulled off with a bearing puller and the shims securely stored an marked which side they came from. The new bearings were heated also and put back into position.Then the diff was finished and mounted to the axle again.
All the measurements I took prior to dismantling the diff were identical after the rebuild.

All in all I must say: it’s a much easier job than I expected before if one does the job in patience and precision.

Chris

[philthehill]

Well done.