e34 medium case diff

[fredbloke]

Would a e34 medium case diff work with my m52 conversion. I have a zf gearbox cheers[/i]

[DanThe]

It wont bolt on if its from a 525i

[fredbloke]

Ahh fair enough. Worth asking theres one up at the scrap yard going cheap.

[DanThe]

If its cheap and an LSD it would be worth paying Gareth on here to swap it over into an E30 case

[fredbloke]

ok cheers. man il have parts going off everywhere

[gareth]

E34 LSD's seem to get a very easy life, not seen a badly worn one yet so if you find the ratio and spec you need in a E34 casing then swapping into a E30 casing makes a lot of sense

Always happy to do this for you

[DanThe]

The slipper I fitted to my E34 was not very good at all, spun a wheel on grass quite a few times

[gareth]

Drifting on someone's lawn? bloody hooligan

[Brianmoooore]

Question for gareth, or anyone else in the know. Can all 188 crown wheel and pinion sets be rebuilt into an E30 case? Are all crown wheels drilled the same, and do all pinion shafts have the same diameters, length and splines?

[gareth]

Pretty much, yes with a few exceptions that can usually be worked around

anything 3.07:1 and higher (lower number...) has a different thickness on the crownwheel. As pinion is a larger diameter, BMW moved the mounting face for the crownwheel across to make room.

Anything 3.15:1 and lower (higher number) is the same as E30 diffs.

So a 2.93:1 diff can have a 3.64:1 ratio fitted but it needs a spacer and longer bolts to be made up and fitted between the crownwheel and diff spool. a 3.64:1 diff cannot however have a 2.93:1 ratio fitted without machining the mounting flange down so thin it'll fall apart.

Some E36 diffs have 14mm bolts instead of the 12mm that's most common. This is less of a problem as it's either a case of opening the clearance holes out on the spool or sleeving them to suit the smaller bolts.

Oh and LSD spools and open spools share the same dimensions so easy enough to find donor ratios for LSD's.

One last thing is, older (E30, E28 etc) diffs have a larger trigger wheel for the speedo sender whereas later E36 etc diffs have a smaller one. So long as the trigger wheel matches the backplate, it's all ok, they are a press-fit on the spool.

BMW are great for keeping things the same! I've build diffs with a E36 M3 (3 litre) spool, E34 525ix cw&p, E30 casing, E28 bbackplate. Or how about a E46 M3 diff with cw&p from an E32 and LSD spool from a E36 M3 evo?

The only thing that cannot ever be swapped around is different case sizes. all parts have to be from the same case size, regardless of what model it's for.

Oh and E46 stuff (apart from M3) is where BMW changed their standard sizes so these are no use to us.


What are you thinking of building up Brian?

[Brianmoooore]

Just filling a gap in my knowledge, so as not to give incorrect advice to members who suddenly find they need a numerically lower diff. after fitting a M5x and gearbox to their cars.
Still the same pinion shaft dimensions and fittings then, whether the rear prop joint is a CV or UJ?

[DanThe]

CV and UJ input flanges are different but it doesnt alter the pinion, they can be changed round, although the pinion preload needs to be reset afterwards.

[gareth]

What he said

It's all very very standardised and logical. Very German