What to make of this....... Diff bearing housings
Turbo Mini Forums

Today I have been fitting a Minispares cross pin diff into a gearbox that has recently been rebuilt by Mr X. The gearbox has only done a couple of thousand miles since.

On removing the diff housing ( housing with studs, type box) there were gaskets between the castings but no jointing compound what so ever. As far as i have been lead to believe, boxes with studs retaining the diff have gaskets between and boxes with bolts do not. Funny thing. Looking at the diff bearing housings there is the start of wear and an ever so slight ridge. Out of curiosity i torqued up the diff housing without the diff or gaskets, measured the roundness of the hole to find it almost perfic round and 0.05mm bigger than the bearing. Gaskets between this would cause ovality of roughly 0.03mm. I felt that for whatever reason, the box had been rebuilt with the gaskets where as originaly it did not have gaskets, this increase in ovality/ clearance of the diff bearing housings caused the diff to vibrate around causing wear on the housings???????.................

One thing that was certain about this box, was, it never held oil, it poured out the bottom as fast as you could pour it in the top. Output shaft seals were not fitted fully home, one was skew, none of the gaskets have jointing compound and the primary gear seal, was, again, skew. All this from some one selling gearbox rebuild services, LMFAO.

I took the decision to not fit the gaskets, Have i done the right thing?

Also when shimming the new diff, the side cover gaskets were slightly thicker than what the book said, taking this into concideration, to get the correct pre load i ended up using two 0.5mm shims, a total shim thickness of 1mm, Does this sound about right???????...........

Your opinions please

so many things to do

Edited by Sprocket on 21st Apr, 2007.

Ive never heard of not fitting gaskets before.
What does the gasket measure when compressed?
Paul

I seriously doubt it!

i have to admit out of everything i've measured before i've never measured the diff bearing housings, only checked that they are a matched pair (and only then if suspected not a pair). From memory the housing should be smaller than the bearing aswell and would appear to have always been the case when i've stripped down boxes.

regarding the side pre-load, i've had to use a heavey shim myself several times as the aftermarket gaskets are a joke. I tend to use minispares gasket sets now which are better than a lot of the others although still heavier than std when measured, the spare ones i got from monkeysport where a joke, infact they are still on the workshop floor.

I've seen the future and tbh its Pie

I am pretty sure the studs vs bolts is NOT a hard/fast rule.

On a pre A-series box (which always had studs) these are all gasketed.

If it's an A+ box on bolts, it's always no-gasket.


If it's an A+ with studs, you need to get out the measuring stick and check if it's a yes or a no...

from what i gather you do have to be carefull as most boxes weas lined bored for the diff with gasket fitted and some was not,

easiest way for preload is to fit diff both side plates minus shimms and then measure gap and add 1 thour for the toatl shim thickness.

but be carefull as the newer type rivited vearings need to be treated as pre a+ and need at least 2 thou pre load as the are the same design as the old style bearings.

on the gasket front it can be very hit and miss personaly i always fit gaskets unless they was none in when i pulled it apart, but i always check for movemnet and clearance.

those cheap gasket are mainly a nightmare for the idler endfloat as you need a hasget thickness of 31 thou but a lot of cheeper gaskets are 35-36 thou

always looking for them bigger bunches of bannanas

use bearing fit to the housings to stop the outer race of the diff bearings from moving

Works a treat or use medium or high strength stud lock locktight

turbo dave and turbo hogster have it.

on the boxes i do i generally fit gaskets if it originally had them, dont if not. - i do measure the tunnel though to be sure all is round and on size...

usually you do find some marks in the tunnels where the outer race has been sitting..

ttfn,
Dave

Edited by icklemini on 5th May, 2007.