Pinion oil seal

[MMT1968]

It’s much easier to change the seal if the diff is on the bench. The main problem is to tighten the nut correctly and have the correct preload on the pinion bearings afterwards again.
The nut must be tightened a bit more than it was before, about a quarter of a turn, but that will increase the pressure on the crush spacer thus giving more preload on the bearings.
To my opinion it’s an amateur‘s way just to mark nut, pinion shaft and flange and tighten the nut to these marks again. The only way to do it right is to change the crush spacer also as long as there is no non colapsable spacer installed. That is a good opportunity to inspect the pinion bearings also.

Chris

[don58van]

Hi Chris

Thanks for your report. I really don't want to pull the pinion out. I have read up on the process of setting the preload and it scared me. To me, it is a complex and mysterious job with critical tolerances. As such, and despite your success, I feel sure I would mess it up. I will see how I go with the crappy amateurs' way.

Thanks again
Don

[philthehill]

Chris
I agree with your comments but for just changing the seal the amateur's way is perfectly acceptable.
So long as the nut is done to no more than 140 lb ft then the crush spacer will not be compressed more than it was.
The hope is always that a solid spacer between the pinion bearings has been fitted.
Phil

[Michiel]

Chris, I'm puzzled. As is often mentioned in his forum and due to new ball bearings having different measurements, you need special measuring equipment and engineers blue marking compound whenever the crownwheel is disturbed?

Could you plaese tell us which measurements did you take and where you bought the four bearings?

[MMT1968]

I dismatled the diff because I wanted to install a LSD and to solve the leaking seal at the entrance. The parts needed were purchased at ESM.
I measured the back lash prior dismantling as described in several tutorials. After removing the ball bearings at the diff cage I measured the thickness of the shims on each side and noted which came from which side. Luckily a friend owns a work shop so I had all the tools at hand.
Changing the diff was plug and play and I used the same shims. The back lash was the same like before and the paint marks on the crown wheel were ok.
So maybe I was just lucky that there were no further issues but I had bought a second crush spacer and a set of shims just in case.
The nut was torqued to 140 ft lbs and I have to run in the LSD now.

Chris