Which diff?

[kdevitt]

Working through an M60 swap into a narrow body Z3 - need to start figuring out the diff to use (running a 420g as well)

The 188 is the easiest option in terms of fitment (would need to use E30 325i half shafts) but is a 188 up to the task?

210 from an E24 / E28 was also suggested- but it’s a bit more custom and potential headache in future if needing to replace bits.

Bearing in mind I’m getting old and won’t be driving like a hooligan - is the 188 the sensible option or one I’ll regret??

[flybynite]

Working through an M60 swap into a narrow body Z3 - need to start figuring out the diff to use (running a 420g as well)
The 188 is the easiest option in terms of fitment (would need to use E30 325i half shafts) but is a 188 up to the task?
210 from an E24 / E28 was also suggested- but it’s a bit more custom and potential headache in future if needing to replace bits.
Bearing in mind I’m getting old and won’t be driving like a hooligan - is the 188 the sensible option or one I’ll regret??

B30 or B40? They used a 188 on the Z3M with the S50B32. The problem wasn't the diff but more so the boot floor pulling apart.

My gut feeling would be a 188 with some sort of twin-ear back plate conversion and floor strengthening which is what I may do on my M54

[kdevitt]

M60B40 - doing the twin ear conversion and boot floor strengthening too. Reading conflicting opinions on whether the 188 is up to the extra torque. Figured it’s what the majority are using - a 210 swap would be a bit of a pain from the sound of it.

[flybynite]

M60B40 - doing the twin ear conversion and boot floor strengthening too. Reading conflicting opinions on whether the 188 is up to the extra torque. Figured it’s what the majority are using - a 210 swap would be a bit of a pain from the sound of it.

I think a lot of these things boil down to how you drive it, there is more torque in the b40 than the S50/S54 but not by a huge amount. Although my E36 M3 had a 210 I dont recall the Z3M or the clown shoe having diff problems.

Are you planning an LSD? Although I like the Torsen I would steer away from it for the B40 as they are not as strong as a good 4 plate.

[kdevitt]

E36 Evo had the 210 alright - 3.0 had the 188. Planning on a non-torsen LSD- veering towards something like a 3.15 or 3.23, don't intend driving it like a nutjob. Whole floor pan is coming out to accomodate the routing for the exhaust anyway - so will get the strengthening and duel mount done at that stage. It makes it the right time to fit a 210 - but prefer the idea of having off the shelf parts available in future, which I'd get with the 188

[flybynite]

E36 Evo had the 210 alright - 3.0 had the 188. Planning on a non-torsen LSD- veering towards something like a 3.15 or 3.23, don't intend driving it like a nutjob. Whole floor pan is coming out to accomodate the routing for the exhaust anyway - so will get the strengthening and duel mount done at that stage. It makes it the right time to fit a 210 - but prefer the idea of having off the shelf parts available in future, which I'd get with the 188

I have to admit that while I think the 188 will be fine, if you are doing that much work to the floorpan I would be tempted to put the extra effort in to work in an e36 M3evo diff carrier mount floorpan section. Keep it as close to OEM M3evo?

[kdevitt]

Needs an E24 or E28 diff - the E36 stuff doesn't fit up, it mounts differently, and then needs custom half shafts - or Z3M ones to be modified. Just makes it an expensive and time consuming job if it throws a shaft. If I use the 188 diff is all bolts up basically and an E30 325i shaft just pops in.