diff

cdavie2002

cdavie2002

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Differential seals & bearings

Looking for a supplier for the bearings/seals for the diff. I'm in the UK.

1975 csi

I'm not sure if it needs sent away to to fully reconditioned or not. Initial plan was to remove side cover and visually inspect internals, then replace bearings and seals and flush out plenty of oil.

It rotates in both directions with ease.

I also want to media blast and paint the casing, I wanted to know how easy it is to remove the internal parts to allow me to refurbish the casing without having to worry about the internal parts.

Also want to check the specs regarding torque for outputs and preload for drive.

Any help/advice greatly appreciated.

Thanks
Chris
 
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Supplier (at least for seals): BMW. Probably bearings as well. Otherwise, take bearing out, measure or read prints, these are pretty standard size bearings so regular bearing suppliers should be able to help. Go for quality (e.g. SKF)

I´ve had it apart. Easy to take apart. Side bearings are relatively easy to replace. Front bearing is as well, but if you do, you have to set the preload afterwards and probably set the position as well.

If it´s noisy, have a professional do it.
If it´s not noisy and not leaking: Change the oil and be done. These diffs are very robust. Paint it on the outside if you must (brush will do), but blasting is really a waste and I would not risk taking a good diff apart just to clean it up to a degree it didn´t even have from factory (and you´ll only see it when lying under the car...). Stock these relied on the thickness of the casting for rust protection. They had a rusty outside even before they went on the car. There are definitely more worthy areas of rust protection on the E9
If it´s not noisy but leaking at the sides: change the seals. Easy to do. Put thread-Locker/sealant on the threads of the side bolts (the driveshaft bolts). They tend to leak through those as well
If it´s not noisy but leaking through the front seal: mark the nut position relative to the input shaft, take nut off, replace seal, nut back on, thighten exactly back to marked position. With a little luck you will not have disturbed the preload and will be fine.

Preload specs and everthing else: In the blue books. You should get these anyway. Everybody with an E3/9 should have them.
 
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Hi, thanks for prompt reply.

There are no noises, so i think Iv decided just to replace the seals and bearings while diff is off the car.

I have marked up length of exposed thread, i will however procure the 'Blue books' from somewhere and check for preload settings & torque for side flanges. I dont just want to rely on the current adjustments, as they might be incorrect....

Can i ask you to clarify for me what you mean by 'set the position' of the front bearing?

Kind Regards
Chris
 
The preload setting is only for the bearings to match to each other. To get the crownwheel and pinion to mesh just right you have to set the tolerances with something like shims (distance rings) I believe. If you change the bearings and the new bearings have slightly different tolerances the pinion and crownwheel may just move as much as to start becoming noisy. Then you have to fumble around with prussian blue and several itterations of adjustments and shimming.
Seriously: it´s easy to have the best intentions and end up with a noisy diff. There´s an art to getting them just right so they mesh perfectly and make no noise (it may even sing despite everything set up just so...).
This is the one case where "while it´s off the car" or "while I´m in there" is NOT the right attitude. change the seals if you must. Don´t touch the bearings and preload if you can avoid it. If a bearing is not worn, does not grumble, there is nothing to be gained from replacing it but much to be lost.
Forget about exposed length of thread. Much to imprecise. At least go for marking on nut and flange.
but really: leave it alone. Chances are way too high that you´ll end up with shiny and noisy instead of rusty but perfect. brush the rust off and paint it with hammerite. Or just leave it rusty if you can...

get the blue books. The diff section is like 30 pages. Ten of which are just about how to adjust pinion and crownwheel. Rethink your plans. Not because of the work involved, that´s just work. but because of the risk of never getting to a satisfactory result
 
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