BMW differential

Dominik · #1 (**permalink**) 07-13-2004, 12:22 AM

good morning,

I wonder huch much torque the BMW diff can take?
did somebody break one?
what type of engines are you running?

Is it the 7-series version of the differential?

thank you,

dominik

Boudy · #2 (**permalink**) 07-13-2004, 08:48 AM

Now isn't that the million dollar question? Well, the answer is that we don't know how much torque it can take because we can't break it.

There are a couple dozen cars at or near 500 torque with the standard E36 suspension and haven't broken. The key is actually to be able to get that torque to the ground to be able to break something. With this in mind, we put drag slicks on and M3 package with 600 torque and made 10 passes. Again, couldn't break it. This car even had the rear bushings replace with steel which made the lanch that much more punishing to the rear end.

DC Cobra is running 600 torque on the standard E36 package as an experiment to try and break the rear end. If it were to break, which it doesn't appear that it's going to, the answer is larger 1/2 shafts for $1,000. If we don't discover the torque range that can break it, we believe the weak link will be the shafts, not the differential.

All in all, these same questions were raised over the Jag and then the 8.8 rear ends because they all origionated on 200 HP cars. We've got enough cars on the road to prove this package and they aren't breaking.

Boudy

Dusty Rhodes · #3 (**permalink**) 07-13-2004, 11:32 AM

why doesnt anyone use the irs from a ford explorer. I was told that is what is under a superformance

Tony Ripepi · #4 (**permalink**) 07-13-2004, 11:49 AM

Hi Guys,

I have had an SPF with the SVO Super Bird rear end in it, put the same SVO rear end into my Coupe and have the Jag rear end in my Unique, both cars are running the Tremec TKO. My Shelby has the Salisbury....... built like a tank and will take all the abuse anybody wants to lay down.

The Ford SVO unit has stood up the best......I feel that the Jag is very good but, if I were going to really big HP I would look to the SVO unit.

Unique........435 ft. lbs. Dyno measured at the rear wheels. 3:54

Coupe.........582 ft. lbs. torque Dyno measured at the flywheel. 3:55.

One mans opinion...

Tony R.

MrMagoo · #5 (**permalink**) 07-13-2004, 06:49 PM

I didnt break the differential per se, but I did break the aluminum wings on the cover that bolt to the frame. I am not running with huge hp, so I dont think that was the issue.

While I had the thing apart I took the E-36 unit out and put in a quaife. I really like the way it handles on curves and in the rain. I had some drivetrain thunking which seems to be way reduced now as well.

Good luck!

Dominik · #6 (**permalink**) 07-13-2004, 11:29 PM

boudy,

thanks - I can use BMW now :-)
I kep an eye on the mounting brackets.

as for SPF cobras built here, the diff is an imported one as far as I know (T-Bird?).

BMW diffs are available all over the show, if BDR/KCC left one or two behind ;-)

dom, cape town - south africa

tony martin · #7 (**permalink**) 07-14-2004, 12:39 AM

MR MAGOO,
I WOULD SUSPECT THAT YOUR DIFF MOUNTINGS WERE LOOSE OR SOFT.(THIS WOULD ALSO ACCOUNT FOR THE DRIVE TRAIN THUMPING).
THESE EARS ARE DEFINATLY NOT A WEAK POINT IN THE SET UP.

REGARDS

MrMagoo · #8 (**permalink**) 07-14-2004, 12:47 PM

Mr Lucky,

I suspect you are right! I think the bolts were not correctly fastened to the differential wings. There was a large washer in between the attaching bolt head and the differential that rendered the rubber bushings in the wing completely ineffective... when I reattached the differential, I fastened the bolt so that it made contact with the bushing, and that seems to be the biggest reason that my thunking has disappeared.

I am generally pleased with the BMW suspension setup. The car handles very well.