Technical 1948 Fiat Topolino Rear Differential

[1948Topolino]

Hey Guys, I need some help regarding the rear differential pinion shims on a 1948 Fiat Topolino. The shims are are external and have no oil seal prior to the shims.

What is the proceedure to seal then up and stop from leaking. There are 4 shims and the are split in 1/2.

Thanks in advance.

 

[bugsymike]

Sounds like a nice project.
I assume these shims control the depth of the pinion into the crown wheel teeth as I can't see exactly from the picture.
In the exploded picture of the diff what is the object just after the bearing with the letter H on it (presumably for dimensions of the bearing) just prior to what looks like a gasket for the flange?
By the way does that end flange have a return drain hole to allow splashes of oil to return back towards the bearings and gears.
I assume there is no obvious provision for a end seal in that last flange?
I know on some very early machines a "reverse scroll" was used to encourage oil to be wound back , also like in some marine sterntube use, a sort of asbestos rope to seal that pressure could be tightened as it wore to maintain a seal.
If nothing satisfactory can be found , would it be possible to use a modern design bearing with a seal built in on the end facing outwards?

 

[1948Topolino]

Yes, the shims set the pinion depth. The "H" is a seal but it is after the shims, so oil leaks out at the shims. The shims are placed at the front of the differential case, between the case and the center section housing. Yes there is a drain hole as you described.

So is sealer used between the shim 1/2s and the shims are a friction seal? It was done that way prior but not working as it leaks.

 

[bugsymike]

Yes, the shims set the pinion depth. The "H" is a seal but it is after the shims, so oil leaks out at the shims. The shims are placed at the front of the differential case, between the case and the center section housing. Yes there is a drain hole as you described.

So is sealer used between the shim 1/2s and the shims are a friction seal? It was done that way prior but not working as it leaks.

The diagram isn't very clear, to me it appears the the bearing in front of the diff housing goes in first then you drop down to the next picture of a spacer tube then a shim? Then the bearing with the H in front of it , then the seal, gasket and flange?
Or am I missing something?
It doesn't seem logical to expect oil not to leak past the shims.
Does the seal run against the inner end of the three bolt drive shaft flange, in which case providing it is in good order then you would only have to worry about oil leaking past the single nut holding the drive flange in place.
So does oil leak from behind the flange or through the lock nut area?