Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) Replacing diff oil seal

Hi
I am a relatively new owner. I have a 1986, 4/4, 4 seater, which I have had for just under a year. It’s in pretty good condition, one previous owner and only done around 28000 miles. Due to COVID restrictions I haven’t had much chance to get out and talk to other owners.
As such I am after a bit of advice.
There is an oil leak which appears to be coming from the oil seal in the diff.
Is replacing the seal a job that I should tackle, and are there any tips or things to look out for?
Alternatively, should I steer clear of it?

Depends where the leak is. Is it on the flange between the backplate & the diff casing then that is relatively easy with liquid gasket or a new gasket.
If on the drive shaft that is much harder. I am sure experts will come along and help soon but here is a guide.

GoMog diff info

From my experience, its pretty straightforward albeit with limited access to do the job but you need to be aware of a few things

1.) I've never actually seen a torque figure for the diff flange nut, so ended up marking up the nut and working out the torque setting. Turned out it was something in the region of 146 ft lb, I think. There's a crush spacer used to set the crown wheel and pinion mesh, so this figure is crucial!

2.) There's 3 types of oil seal so make sure you get the right one, from memory, one at 6 quid, one at 12 quid and one at 40 quid!

3.) Its very unlikely the old seal will come out as one! Be prepared to take it out in bits!

4.) Finally, check the breather hole on the rear axle tube, its a small 3mm hole which easily gets filled up with muck and causes the axle to pressurise

Arwyn

Which begs the question, how do you determine which type of lip seal is fitted is to the pinion shaft of your Salisbury Diff.? To ensure that everything is at hand before you start the strip down

I've done three MGB diffs, all Salisbury. In each case, there was only one seal available, although this was years ago. Probably best to get the old one out for examination first.
As Arwyn said, a collapsible spacer sets the pinion position, and if you over tighten beyond that point, it should either be replaced, or I do know one case where it was removed and de-collapsed, then reused. But this is hassle.
The ones I did, I marked the nut and flange, counted the turns off. Changed the oil seal. Counted the turns back and tightened until the marks aligned.
The second one was little more than finger tight to be honest , just nipped up from that. A bit of Loctite to make sure, but it was fine.

So where does the 146 ft/lbs come in ?

For seals, I would suggest contacting the Bellingers at JB Sports Engineering

I marked the nut and the pinion shaft with aligning marks using a straight edge and TCT scriber and it took 146 ft lb to move the marks out of alignment.

Arwyn

Does that mean I do not need to use a torque wrench, just mark the pinion shaft and nut positionally, count turns made in removing the nut and replace to the same values ?

Thats how I did it. There was a lot of correspondence at the time on the MGCC grapevine after a few V8s had the roll pin collapse, and destroy the diff, so it was headline news for a while.