thrash

I've been doing AKTE research persuant to putting together some D2 A8Q 6MT swap info (no, i dont have an A8, and no, i don't have it all figured out. I've read the archives and im just as frustrated now as i was 1 yr ago when i asked about it

So the USA market A8Qs came with a few different final drives, but all were either 37/10 or 37/9, with only the S8 getting the 37/9 gearset (tcode EUU)

However, the transmissions show a completely different set of ratios - either 34/11 for S8 transmissions (tcode FBG) or 30/11 for all other A8 quattros.

I've seen a hint of how there is some magic happening int he A8/S8 gearbox that makes the ratios "ok", even though having a 34/11 upfront and a 37/9 in back seems totally broken. Can anyone explain to me what the disparity is between axle ratios and tranny ratios on the A8 ?

Other interesting info:
The EUU S8 diff was cross listed for the following applications:
EUU A6 06/00 -
EUU S6 06/01 -
EUU S8 11/00 -
EUU Passat 12/01 - 04/02

If the multiplicative effect is a function of the A8's auto transmission, then persumably if one wanted a 6MT transmission to swap in, one would choose it based on a matching ratio to the rear axle, i.e. if i want a gearbox t match an S8 37/9 rear end, i want a 37/9 manual gearbox?

From what i've found so far, there are the following 37/9 6MT boxes:
EDU on A6Q 05/99-05/00 (6MT)
EDU on S4Q 07/99-10/00 (6MT)
FTG on S4Q 04/01-09/01 (6MT)
FTG on A6Q 06/01 (6MT)

naturally these gear boxes are bolting up to the 2.7T V6, while the A8 will have the 4.2L V8.

What is interesting is that the A6Q only has one floor pan P/N, irrespective of manual or automatic configuration. This suggests that an A6 transmission swap wouldn't require hammering/cutting of the body sheet metal to fit things.

One frustrating thing is that while the A6 and A8 both share 4.2L V8s, they have no common engine codes. I would have to suspect that the engines are similar, but without being sure it's hard to suggest that an A6 tranny would bolt up to an A8 engine.

There also do not appear to be any automatics common between the A6 4.2 and the A8 4.2 - the 4.2 trannies for the A6 shown are FBD (S6) and FUL (A6). Neither of these has any other application.

As you can see from above, there are a wide variety of ways to get an EUU 4.11 rear diff, which is specified for the S8. There are also a variety of ways to get a 4.11 6MT. The question then is which of those, if any, bolts to the A8 4.2 block ?

If none of them bolts, is it possible to make an adaptor plate ? what is the installed length and position of the 2.7T vs the 4.2L ? E.g. if the 2.7T is shorter and sits further up front than the 4.2, perhaps a bellhousing adaptor can be fitted onto a 2.7T 6MT to allow it to fit the 4.2 ?

Regarding the driveshaft issue - what is the objection or hesitation to having a driveshaft custom made ? It doesn't seem that this would be necessarily more expensive than getting a new DS from audi If one is willing to go the route of getting a custom DS prepared, then what prevents one from trying to do the manual swap on an A8L ?

It would be sweet to make your own 6MT S8L

Are there any mechanical issues i am overlooking ? If there is a workable plan for the mechanics, then it seems that the electronics would also be possible, but would require real parts instead of just theory

GDJT Allroad^2

He came up with a link to a site that had a guide about all kinds of Audi transmissions and explained the ratios. <a href="https://forums.audiworld.com/a8/msgs/17768.phtml">This is the original Manaul Swap thread</a>.

The final drive ratio of a ZF transmission isn't the same as the ratio given by the torsen diff which is the ratio that has to match the rear diff. <a href="http://www.elektro.com/~audi/01E/">Everything you wanted to know about Audi manual transmissions but were afraid to ask</a>.

I don't think anyone had an issue with a custom driveshaft, but if we're going with stock parts, (the ZF 6 speed and rear diff) it would make sense that the stock driveshaft would fit the application.

I thought all S8s were SWB cars and not "L" cars?

A swap with the B6 S4 drivetrain would make the most sense to do a conversion these days.

PaulW

The gear things are easily figured out....you could always get a rear end from Europe, where all the A8/S8 4.2's came with the 37/9 gear set....only the US had the tall gears.

Or if the gears are the same, just get any Audi rear meatball and swap out the gears.

As go gadget states, I believe the torsen corrects the final drive front to match the rear.

One thing that you didn't state was how you will interface the TCU/ECU.

I think I finally figured that out when a guy with an A6 2.7 came over....they have different ECU's for the A6 2.7T manual and automatic.

So not only would you need all the parts, but you would need a TCU from a six speed manual A8/S8 plus an ECU from a six speed manual A8/S8 plus you would need to modify the wiring harness to make it work (which would require the schematics).

And since this was only performed on pre facelift A8/S8's, it could be significantly more difficult to do this with a post facelift car because of the different wiring and CAN bus configuration that the pre facelift cars did not have.

The rest of the stuff you posted is easily figured out, you just have to do the engineering....which would take some time.

So, would you rather have a supercharged A8 or a six speed manual???

pw

thrash

have a manual. In any case, it's not like a manual and a super charger need be mutually exclusive.

I don't want the car to go faster (although that would probably be a side affect). I want a proper transmission in it - better reliability, better driver involvement, better predictability, less maintenance.

I can't in good faith consider an A8 until there's a real gearbox in one. Especially since the slushers in A8s seem so willing to fail on people.

I am not worried about the ECU / TCU either, i figure worst case i develop a stub TCU that lies to the ECU about the things the ECU and cluster care about, but i figured i'd check here to see how to resolve the mechanical issues.

I am not sure CAN makes things harder - CAN might make it _Easier_. I'd rather leave the wires alone and just fix the software, if we're talking about more than about 4 wires

What I'd like to do is take a post lift A8 or A8L, put an EUU on it, and then get a 37/9 6MT that bolts to the 4.2 block. Do you know which gearbox that might be ?

If that all fits up, then i'll worry about the electronics.

Thanks,
Matt

PaulW

There are loads of parts you'll need, transmission mounts, clutch pedals, etc., etc.

Any 01E box will bolt straight up and work....you'll find the link to more info under go go gadget's post.....

And I would think you'll take at least six months to source the parts and do the install. Not to mention at least 6K.

When it's done, please document it, I'll pay you for a copy of the plans!!!!

Go get em!

pw