Not sure what chart you are referring to, just taking his 520 Nm quote and converting it...
 

Every Nm is equal to about .73756 lb. ft. of torque. I get the conversions from a bookmark I recently had to update here:<ul><li><a href="http://www.forcecontrol.com/conversions.htm">http://www.forcecontrol.com/conversions.htm</a</li></ul>

The chart is in the URL of the post you replied to above
 

In any case your data are correct, if The Brit and his URL chart are correct. The chart shows a maximum engine torque allowance of 520 Nm for the tranny specified by The Brit. 520 x .73756 = 384 lb ft, just like you said.

Why is that? Maximum torue from the RS6 engine is rated at 415, and 384 is 31 below that. What gives? Can anyone explain?

It does... sort of (more)
 

If you read the linked artice's section 4.3, it states "<i>Extensive measurements on public roads were evaluated. These showed that current traffic conditions do not allow long periods of full load running, enabling the test times of the high torque range to be significantly reduced</i>".

To me, this indicates that the stated torque rating is a continuous rating, not a peak rating. Given that the RS 6 produces 560Nm (413lb. ft) peak torque, this would tie in with the 'allowable' peak over the stated torque rating.

However, although ZF don't think peak loading is likely to happen often, I think everyone overlooked the fact that the RS 6 has such a wide peak torque band - I think it's entirely possible to run the transmission on an RS 6 at peak loading for considerable percentages of it's drive-time.

It's been said that MTM trashed several gearboxes on their test RS 6 while bumping up the torque, and there have been several reports of stock RS 6s gearboxes failing (my business partner is one of them) - does this suggest that the stock RS 6 runs the box close to or slightly over it's maximum rated value enough to expose any weakness in the gearbox build? Does this mean a weak gearbox <b>will</b> fail if the host car is tuned? Possibly.

Before anyone starts pointing to RS 6s that have been tuned well above 413 lb. ft and haven't broken their gearboxes, just remember that ZF's stated vales are probably calculated to give a &lt; 5% failure rate or something, meaning that the vast majority of 5 HP 24 boxes will accept more peak torque to a greater or lesser degree, and for a greater or lesser duration.

Just some food for thought...

Well, way to dash my chip daydreaming of late. For once...
 

will Audi please build a tranny with some decent headroom, please.

The A8 has a great Tip box - 6spd and something like 2600rpm at 100 in 6th gear
 

And given that the A8 4 litre diesel V8 doesn't produce much horsepower (274hp) but kicks out a stunning 650Nm (480 lb. ft) of torque, the A8's 6-speeder box must be able to comfortably handle that kind of torque, which makes it possibly a 6 HP 32, or a slightly over-torqued 6 HP 26.

Now, either we need an A8 gearbox in an RS 6, or an RS 6 engine in an A8.

I did find the link below (posted separately as it made the page too wide!), which indicates even lower input torque values. If Audi are starting to use the 6 HP range, the allowable torque does appear to be higher across the range, which is good news.

ZF link
 

<ul><li><a href="http://www01apps.zf.com/kst827/ZF_ProduktDB/view_produkt_prod.asp?lang=en&amp;bgcolor=0&amp;la ngID=2&amp;doSendAnwend1=1&amp;anwendID=18&amp;doS endBereich=1&amp;bereichID=null&amp;doSendFelder=1 &amp;geschaeftsfeldID=null&amp;doSendPr

"we need an A8 gearbox in an RS 6, or an RS 6 engine in an A8," I'd prefer the former, please.

If we're dreaming, I'll have one of each please.

This link didn't do much
 

I got a spartan-looking page, clicked on a couple of places that were clickable, but got no useful info

Try this
 

ZF have some sort of session state that gets broken in a posted link. You can go to ZF's homepage (<a href="http://www.zf.com/">http://www.zf.com/</a>) and click on Products For, then Systems, then Cars. After that scroll down and there's link to 4/5-spd transmissions.

After all that effort, all you get is the following table &amp; some German language PDFs.

Type Type of prime mover speeds(forw.) Input torque(Nm)
4 HP 20 Front 4 330
4 HP 22 Standard/Heck 4 340
4 HP 24 Standard/Heck 4 450
5 HP 18 Standard/Heck 5 300
5 HP 19 Standard/Heck 5 300
5 HP 19 FL Front 5 310
5 HP 19 FLA Front Allrad 5 310
5 HP 19 HL Heck 5 310
5 HP 19 HLA Heck Allrad 5 310
5 HP 24 Standard/Heck 5 420
5 HP 24 A Front Allrad 5 470
5 HP 30 Standard/Heck 5 560
6 HP 26 Heck 6 600
6 HP 26 A Heck Allrad 6 600
6 HP 32 Heck 6 750
6 HP 32 A Heck Allrad 6 770