[sajakh]

Just browsing on the Alpina site, I noticed the new B7 has the old 6-speed auto tranny used on the 750i, 6HP26. The B7 engine which is a supercharged 4.4L V8 has a power/tq rating of 493 hp/699 Nm.

The interesting part is that the 6HP26 is rated for a torque capacity of 600 Nm!
So it seems that Alpina felt it was OK to use this auto tranny.

http://www.just-auto.com/article.aspx?id=90340

The 335i uses the 6hp21 (by BMW speak its 6hp19 TU), its rated at 450 Nm (331 lb-ft).

What does this mean?

[zenmaster]

Apparently, Alpina believes the 6HP19 TU is good for 500NM - same with the 6MT (ZF type G). Just 2nd hand info from the m5board.

[Black Chili]

I don't know how ZF does theirs, but transmissions will generally take a lot more short term load than rated for, it just depends on the load. Keep in mind also that an automatic won't generate the same drive train shock as would a manual (well without a line lock and some tweaking, but I digress).
I also find it very difficult to believe they'd use a transmission rated at 331tq; the 516tq model would seem way more appropriate. Either someone is playing games with the numbers of ZF maybe rates theirs under some designated criteria we cannot readily achieve- at full load for 1 hour at 150 degrees ambient.

When Ford built the 03/04 Cobra they had a durability test where the engine would fail at wide-open throttle and 100% load at peak power; I believe it was 40 minutes. The problem was, at WOT, the engine would consume 15.5 gallons, the size of it's tank, in something like 6 minutes. The ZF may be rated along the same lines and what we're doing is simply eating into the built in margin.

Just wait a little while for people to blow up the engines and toast the transmissions, it'll happen sooner or later; then we'll know where the limit is, under what conditions and how to avoid it. We pray silently for those of you who sacrifice your ring landings so we may better understand the car