Place your bets now! 500whp+small case welded = ?

[SLEEPYDUB]

So I've got this 3.91 welded small case diff laying around. I currently have a 3.73 LSD (LSD seems to be failing, as it feels like its spinning one tire, on drag radials).

I've got a 2JZ with around 500whp, maybe more. Lets see how long this small case will last on that power, with a welded diff, on 245/50/16 drag radials.

What do you think will break first?
Diff? Or axles?

We will find out soon enough just how much power this small case can handle! Stay tuned!

[SLEEPYDUB]

Verdict is in.

Something has failed. When the car decelerates it whines like no ones business. Like so loud I'm sure everyone outside of the car can hear it. Its a very high pitched whine.

Sounds to me like pinion bearing.

Ill be pulling this diff out this week to see what actually happened.

[xwill112x]

Love your style.

[Herr Faust Schinken]

Is there that big of a power handling difference between small and medium case doffs the medium case diff seem to be able to take a lot of abuse.

[SLEEPYDUB]

From what I've read small case can handle 240ft/lbs torque, while the medium can handle 480 or something like that.

Either way both are too weak, I just wanted to see how long a small case would last. Not long...

[Wanganstyle]

BMW Medium case can take LS7 abuse; much more sheer instant torque stress than any 2J application. There are several 500hp+ (non turbo, big displacement built LSX) cars in the bay area running 188mm medium case units with STOCK gear sets.

BMW stock 188mm gearset has also been ran in drag racing use to over 1krwhp (turbo BMW GTX45R) - bay area local did 30 passes in the 9's before the LSD center wore out- gear set was still good.

If you really need a larger gear set you can weld to fit a 210mm rear end unit from a e28 M5 or similar; those are similar to the supra TT units in size.

MK4 Supra TT Automatic and Non-turbo Supra/Lexus GS is a 200mm, supra TT 6mt is a 220mm. My JZZ30 2JZ-BPU swap car had a 200mm 3.91 ratio setup with TRD/OSGiken LSD unit.


The toyota 200mm gear sets don't break often if at all, I have seen them last over 800rwhp. The BMW 188mm gear sets are almost the same size and arguably better surface finish items - german metallurgy is not any less advanced than the japanese gears.

[SLEEPYDUB]

Thanks for the info.

What are your thoughts on the Z3 Torsion diff? I can get one for $250 and it seems like a nice unit.

[Wanganstyle]

Thanks for the info.

What are your thoughts on the Z3 Torsion diff? I can get one for $250 and it seems like a nice unit.

the BMW torsen unit is a Belgium made Zexel, Toyota actually owns Zexel LOL

its quite strong, much stronger than the rx7 twin turbo and seemingly even the toyota torsen units although I have not broken any torsens at all myself.

a local ran the bmw 188mm zexel unit to 9.6 and 9.4 sec 1/4mile times; it just did not hook up as well as the high lock clutch units - holeshot improved and the car was 9.4-9.2 after the clutch diff conversion (gearing stayed identical)

[SLEEPYDUB]

Nice! Looks like ill be picking this up then. Thanks for the info!

[Wanganstyle]

Nice! Looks like ill be picking this up then. Thanks for the info!

its a smart idea for a FWY racer; if you don't care for the holeshot (or worry about breaking axels) then the torsen will be a good unit for your needs -it is also 0 maintenance and cannot be rebuilt; there is nothing to wear out!


I'd also suggest buying a second ear mounting kit for the e30 stock diff; the LSX e30 kit guy designed a really nice piece - you will need to equalize the stress on the rear cover or you will be breaking the single left ear.

[SLEEPYDUB]

I've been looking into that cover.

This car is mainly a drift car. Will the Z3 one be OK for that also? I'd like as much lock up as possible. Have been considering a welded medium case also.

[Wanganstyle]

I've been looking into that cover.

This car is mainly a drift car. Will the Z3 one be OK for that also? I'd like as much lock up as possible. Have been considering a welded medium case also.

Buy that cover add on- its really nice. A local guy has one of those entire kits, fit and quality is very very nice.

If you are looking to drift don't bother with the torsen. It is not setup for drifting; its good for HPDE track work and great for street use.

Medium case + welding will be your best cheap pick for drifting. The spool factor vibrations are pretty vicious....I fitted a welded to my e30 a few weeks ago; its hooning fun. turns slowly and handles terrible though- understeers worse than a torsen pre lock up.

High locking LSD is the ideal setup for drifting costs are very high in comparison to a welded. 2 way 4-5 clutch disc low ramp angle would is wicked fun for drifting; higher entry and exit speed potential