Diff choice for turbo conversions

[AG205]

I know plenty of people on here have done turbo conversions or are running high bhp NA engines in their E30s but what diffs are you using?

Can anyone tell me how much torque a standard 325 Sport LSD can take because I would have thought that if you are running anywhere near 200-250Nm (or above) it would just poo itself and let go?

Has anyone tried using medium or large casing diffs, E34 or E36 or even a diff from another manufacturer (cosworth 2wd)?

Cheers

Andy

[FormerMember]

E30 typ188 diff can take +500hp / Nm easily. Of course you can break everything but with sensible use it's surprisingly durable.

Driveshafts usually break sooner than the diff itself.

[AG205]

Bloody hell. I was told by some BMW 'expert' that I'd need a large case (220) diff if I was after any real power. Wasn't too chuffed with this advice as fitting one would presumably mean remanufacturing the back end, probably custom driveshafts, fuel tank/spare wheel well clearance problems, subframe redesign etc etc . Not fun unless you're after huge bhp.

I was thinking about going for a medium case E36 M3 LSD as there would be more chance of fitting it under the E30 without major surgery to anything but the subframe.

Are you using an E30 LSD with the V8?

[Gunni]

Just use what you have and get a different ratio if you really need.

I had a 3,73 with a 260 325i box and 400hp on tap, it felt totally fine although cut short at 6500rpm@~150mph. But not really a reason to go much faster then that anyway in that case.

[e21Jason]

Medium case e36 is the same internals as a medium case e30 only upgrade is the large case
also big power will also effect every thing in the drive train so sometimes it's cheaper to break halfshafts rather than diffs

[AG205]

Nice one that's really good news.

Should save me a bit of work.

Cheers.

[FormerMember]

Are you using an E30 LSD with the V8?

Yes, i bought brand new typ188 3.07 diff from BMW. It should be fine, but i'm afraid my driveshafts will break. Gotta buy new ones as soon as i can spare some money..

[AG205]

A new diff must have been rather pricey. What sort of torque are you running then if the driveshafts are near there limit?

I'm hoping to use the internals incl. LSD from a E36 M3 3.0 3.15:1 and stick em into my 325i sport LSD. Do you reckon it'd be easy enough to do a DIY swap? I have stripped one of these diffs down before and there's really nothing to them as far as I can see and if the internals are all a direct swap the only difficult bit should be getting the backlash right? Am I right or is this a bit optimistic?

Andy

[Gunni]

BMW E30 axles don´t let go unless you launch of the line with 26inch slicks.
People drive fine with stock ones on the street with well over 700nm

[FormerMember]

Swapping the internals is not hard thing to do, but you need to know what you're doing to get the tolerances right = quiet and durable diff.

BMW E30 axles don´t let go unless you launch of the line with 26inch slicks.
People drive fine with stock ones on the street with well over 700nm

The axles itself are fine but the CV-joints break too easily in hard driving.

[Gunni]

I have not seen that happen, even people doing 7k launches off the line running 26inch slicks.
Reaching very nice 12.04sec 1/4 times.

And pulling 0.7sec 60fet times. This is the most torque that can get through the CV joints.
As you have the torque at 7k at full boost * gear ratio * diff ratio

[AG205]

I've been quoted £150 (+VAT) for swapping the diff internals over which didn't sound too bad but if I can find a guide on how to set a diff up properly I'll probably try it myself. Only thing is it's an expensive mistake if I cock it up.

Also been told that if I put the 3.73:1 E30 internals into the E36 casing (+LSD) it might be worth selling as E36 M3 owners are after high ratio diffs as an upgrade. Don't know if anyone else might know if this is true or not?