Gearbox replacement

[Fredde]

Hello I have a A8 d2 with a failing ECZ gearbox. Current symptom is converter shudder at low throttle around 2000-3000 rpm. I am wondering if I can replace this with a FUL box from an a6 4.2 2002? How would I know if they are compatible?

[MikkiJayne]

I reckon this will work just fine. What's critical with the 5HPs is final drive ratio, as the internals are all the same. The TCU is programmed to know what rpm should be coming out relative to gear selected and rpm coming in. If you have the same final drive between the two (which you do) the TCU will never know the difference.

ECZ transmission goes with DUR & EUS final drive 3.7:1

FUL transmission goes with EUS & GME final drive 3.7:1

[Fredde]

Originally Posted by MikkiJayne

I reckon this will work just fine. What's critical with the 5HPs is final drive ratio, as the internals are all the same. The TCU is programmed to know what rpm should be coming out relative to gear selected and rpm coming in. If you have the same final drive between the two (which you do) the TCU will never know the difference.

ECZ transmission goes with DUR & EUS final drive 3.7:1

FUL transmission goes with EUS & GME final drive 3.7:1

MikkiJayne thank you for this answer. So for the basic function this would be a feasible swap. Next question then is if I should worry about any installation issues with mountings, electrical connectors or similar in mowing it from the A6 2002 to my A8L 2000. Also this is a used transmission said to be working before removal but I am planning on rebuilding it. Any recommendations on where to get a rebuild kit and what parts need replacing?

[MikkiJayne]

You will need to swap the D2 mounts and hardware over. F125 is the same.

I would get the converter reconditioned for sure because it sucks when you swap the transmission and then have to take it out again to replace the converter. Don't ask how I know that!!

Clutch packs are fairly easy to get, mostly aftermarket now as I believe ZF have stopped selling parts for them. Exedy make some, and there are also some Polish kits. The main thing if you have it apart is to check the condition of the first roller bearing and first clutch basket snap-ring groove. If they are ok, new clutches and seals and it should be good to go.

I've heard good things about the Transgo pressure valve upgrade too but not personally fitted one yet. If the replacement transmission is working then now is the time to fit the Transgo valve as it should prevent any pressure issues later on.

[Fredde]

Hello I have now bought the used transmission and also the transgo valve upgrade and also an upgraded A clutch basket. This first roller bearing you mentioned which bearing exactly is this? Do you have a PN or some source for it? I’m thinking I will just go ahead and buy one since when I start disassembling the gearbox I don’t want to get stuck having to wait for shipping incase something requires replacement.

Originally Posted by MikkiJayne

You will need to swap the D2 mounts and hardware over. F125 is the same.

I would get the converter reconditioned for sure because it sucks when you swap the transmission and then have to take it out again to replace the converter. Don't ask how I know that!!

Clutch packs are fairly easy to get, mostly aftermarket now as I believe ZF have stopped selling parts for them. Exedy make some, and there are also some Polish kits. The main thing if you have it apart is to check the condition of the first roller bearing and first clutch basket snap-ring groove. If they are ok, new clutches and seals and it should be good to go.

I've heard good things about the Transgo pressure valve upgrade too but not personally fitted one yet. If the replacement transmission is working then now is the time to fit the Transgo valve as it should prevent any pressure issues later on.

[MikkiJayne]

this one:



There's an upgraded part from ZF compared to what was originally fitted. If you can find the ZF parts catalogue for the 5HP24a (its on the web somewhere) you can find the ZF number for this instead of the Audi one.

[Fredde]

Thank you so much also what about the solenoids on the valve body? Any reason to do something about those? Recently watched this guy M539 restorations on YouTube to the valve body on his bmw and it apparently helped a lot with shifting. I just really want the gearbox to be like new and last a long time.

Originally Posted by MikkiJayne

this one:



There's an upgraded part from ZF compared to what was originally fitted. If you can find the ZF parts catalogue for the 5HP24a (its on the web somewhere) you can find the ZF number for this instead of the Audi one.

[MikkiJayne]

I've never touched the solenoids tbh, but if it helps in a BMW 5HP then I'm sure it'll help in ours too.

[donp38]

Has anyone the part numbers for complete gearbox and torque converter?
2001 S8..

just thinking Audi tradition may have them?

[MikkiJayne]

Tradition have an S8 torque converter for a mere €1400. A few assorted 5HP24s for ~€7000, but no S8 versions.