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Discussion Starter #1
I feel like my car is fighting me at the moment...every time I finish a job, something else fails within days.

I’ve just had some bushes replaced and there’s been a faint metallic rotating sound since. I thought/hoped that it was caused by a brake disc rubbing on a dust shield, but the noise suddenly got a lot worse today with a graunching at low speed. I’ve had the car up in the air and spinning the wheels, it seems that the noise is coming from the diff!

This is quite frustrating - but I’m determined to not let the car defeat me.

So I might as well take the opportunity to change over to a 750/850 diff, but I’m struggling to find any information on European/UK specific diffs and compatibility.

I can get hold of a diff from an e38 M73 at a reasonable price and known good quality part. Would this be a straight swap?

I also tried accessing the e31 workshop manual this evening - to see what the procedure is for refitting the diff - and the link which I usually go to now takes me to BMW tech info and is asking me to pay. Does anyone have a working link to this?
 

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Discussion Starter #4
I’ve sourced a 3.45:1 diff from an e32, hopefully this will be compatible given that it’s from an e32.

I don’t do motorway driving in my 8er, so not too fussed about high revs or MPG.

I can’t find much online about this having been done this side of the pond - but I need a solution promptly and can’t wait around for an e32 750 to crop up.
 

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Those E32 750 3.15 diffs are like hens teeth. I would love to do the diff swap at some point if I get a hold of one.
 

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Discussion Starter #6
Yes, that certainly seems to be the case.

I’m not fussed about having an LSD, but I would like the car to feel a bit less hesitant/overweight when moving away. I know that the 3.15 diff achieves that and that people still report only small increases in engine revs at cruising speed. I don’t do much motorway driving at all, so I’m not overly concerned about mine becoming excessive.

That said, I did have a look at a gearing calculator earlier and the results weren’t much different even with a 3.45 final drive.

I’ll report back here either way.
 

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Discussion Starter #8
I just thought I’d update this thread for posterity.

The diff swap was completed - a piece of cake! I managed to get a 3.45 diff from an e32 735i. I put my old back case on it, swapped over the front bracket and replaced the oil seals and gasket.

Had my first drive this morning and it’s a great improvement, and very cost effective. Total cost was just £340 including seals etc.

It really has made a great improvement to how the car feels at low speed - it just feels lighter and less hesitant when moving away. Wish I’d done it ages ago!

I’d recommend this to anyone, given the additional cost and rarity of the 3.15 diff.
 
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