Repairs to BMW 850 Differential Oil Seal & Centre Bearing

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This afternoon was taken up repairing a differential oil leak on a BMW 850 CSi – as it was a lovely day we know it was going to be hot one in the workshop!

However, not to worry when you know that someone else is going to have to sweat as well given that this job is definitely something that needs additional help to remove the full exhaust system – always a bit of concern here as these original systems have been in place for a few years and need to be taken down with real care avoiding any cracking or bending.

Needless to say, this German lady of the road will almost definitely need new support brackets.

Once the exhaust was removed it was easy to see the propshaft and centre bearing heat shields etc.  Now out with the marker pen (as when removing any thing from the prop, mark-ups are needed to record the alignment as this piece of kit has to go back exactly as she came off).

Prop removed but then time to split the shaft by removing the 17mm nut in the middle of the shaft – as ever super tight (and a good job i had those extra Weekabix for breakfast)! Time to pull off the centre bearing again watching how this one comes off (time of the marker pen again) ensuring the spacer ring goes back in.  Pressed on the new bearing (ensured she is the correct way round)  – re joined the ends of the shaft – again ensured all your markings align up.

Propshaft ready to back in to car. Before any further work of course, its time for tea and biscuits!!

Ok –  refreshed!

We then had to clean the diff off which had very bad diff oil and heavy grease all over the place. A simple tip that we learnt years ago (and which can save hours of anguish) is to ensuring the open end of the diff is covered from any flying rubbish the during clean off!

Time now for some super efficiency and as if by magic the draw opens and low and behold, a spare gasket appears for the shaft – these ‘little chaps’ have habit of tearing and hence we have to keep a stock of these ordered up from BMW.

After the Ali Bongo show it was time for a bit of physical labour again – the hub had to be removed from the diff. As it was on a splined shaft, the old marker pen was out again as was something to tap this hub off as she was tight – all whilst taking care not to damage anything.  With the hub off, out with the tight seal whilst avoiding any internal damage to the diff case with the extraction tools – sometimes it makes we wonder if the job description should be ‘surgical skills needed for man with Popeye forearms’.

Finished everything off by refitting new seal, pressing in with a soft hammer and a little grease smeared on  the outside of the seal case.

Then simple reassemble the whole lot back on to the car.

Another BMW 850 CSi back on the road and time for another challenge.

Latest Blog September 15th 2009

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