Delta between helical and clutch-type LSD?

In reply to G_Body_Man (Forum Supporter) :

Thanks! I thought the 128i used the same rear end as the automatics (3.23 gearing with a traditional, 4 bolt to drive shaft assembly). I know the 135i has a weird rear end. 

G_Body_Man (Forum Supporter) said:

Also keep in mind that if your 1-series is manual, the ring gear is welded to the carrier. A diff out of an automatic car uses a bolted ring gear and will give you a slightly shorter axle ratio while permitting the installation of an LSD.

I had no idea! Crazy...

I went through this last year. Not many options for the 190E 2.3-16 out there.

One option was a Wavetrac (helical) diff. On paper, it sounds like it should work better than a clutch-style LSD. But all the guys I race with in the BMW CCA use clutch-pack diffs, even though they have other options. They convinced me I would be unhappy with the handling of the helical diff in a front-engine/rear-drive racecar, though I can't honestly say I understand why.

One argument I can understand is that clutch-style diffs can be relatively easily/cheaply rebuilt. Once the Wavetrac wears, you have to replace the whole unit (at significant cost). Then again, it probably lasts longer...so this might be a wash.

G_Body_Man (Forum Supporter) said:

Also keep in mind that if your 1-series is manual, the ring gear is welded to the carrier. A diff out of an automatic car uses a bolted ring gear and will give you a slightly shorter axle ratio while permitting the installation of an LSD.

I don't think that is STX legal though.