Front diff housing side covers

[poly_cab_hafs]

Folks

I am in the process of restoring an old (1964) running gear that I have.

I need to replace the side covers on the front differential casing as both sides are damaged (due to the swing arms being allowed to travel past their limits at some point).

I have spare side covers so that part is not a problem.

I was wondering if anyone had experience of conducting the shim calculations that are described in the repair manual. The shims are required to ensure precise location of the crown wheel in the diff housing against the pinion etc.

The question is really how critical these calculations are. The diff that came out of the housing is in good condition as are the bearings. These are already shimmed for the old housing covers. To do this properly (against the difficult to understand instructions!) will require pulling the bearings of the diff etc.

I suspect the risk of incorrect shimming is damage to the side covers or excessive wear of bearings in the pinion etc.

I do not have a platform for this running gear and it may never see a platform. So may never turn a wheel. And if it does it won’t exactly be doing 10k miles per year..

With that in mind I’m inclined to chance trying new side covers onto the diff with the old shims/bearings etc.

Any thoughts?

[AustHaflinger]

I have dismantled my front diff and replaced some bearings - but reassembled it using all the same components so all settings remained the same - so I am not much help and I suspect there is not too many on here who have done this as well.

I have to agree with you that the manual is a horror and is almost impossible to use.

Good luck

Garry

[heinkeljb]

Not having taken my front diff apart (yet), I can't give you any definitive methods to deal with the issue, but I think what I would do is this:-

Take one of the old side covers and measure the distance from the surface which bolts to the front diff casing to the surface of the bearing which goes in to the diff casing.

Now do the same for your new side cover. Take the same measurement. Depending on if it is the same or different will tell you if you need to change the shims or not. If the distance on the new side cover is bigger than the old side cover by more than 1mm, then you will need a thinner shim by how ever much the difference is. Shims only come in 1mm thicknesses so you have to err on the side of too loose i.e. when the cover is bolted up, the bearing and shim must not be pressing on the differential harder because the shim is 1mm too thick.

If the distance is smaller then you need thicker / more shims so the side cover is holding the differential in the correct position in the Front diff housing as the old side covers did.

You now have to do the same for the other side. - The aim at the end of the day is to keep the diff in the same place with in the diff housing as it was when using the old side covers. New side cover might be machined with a different depth for the bearings from your old side covers.

Obviously if shims only come in 1mm thicknesses then you have to err on the sloppy side or the diff will bind up when it gets hot.

Hope this helps,

John

[poly_cab_hafs]

Thanks Guys

I do intend to measure the relative distance between the mating surface and the bearing face. I have a number of diff housing covers so I wanted to choose those most similar to the current broken covers in terms of size.

The broader issue is that the repair manual works to very precise measurements - in some cases 2 decimal places (mm) which is very difficult to achieve for me in reality. The shim sizes are actually rounded up to 0.1 mm increments in the repair manual and not 1mm.

I think this is, more generally, the issue I have with the repair manual. The reasonably difficult to follow text coupled with levels of tolerance that are desired.

[heinkeljb]

My apologies, didn’t look properly at the measurement sizes. The ideas involved are correct, but as you say .1 is very small. You really need a micrometer to use to do the measurements, but if you can get hold of one it shouldn’t be anymore difficult. I think the biggest issue would be getting a micrometer that measures depth.

John

[poly_cab_hafs]

John

The tail of a vernier calliper will do my job!

I will report back if I burst any diff housings for being 0.1 mm out!

d