B6 A4 Manual transmission swap

[lean_wean]

I’m starting a build on my 2003 a4 1.8t Quattro stage 2+ apr. I blew my second auto trans so I decided I need to swap in a manual trans. I got a 1998 a4 2.8 Quattro with the 5 speed as a donor car. And ordered a new south bend stage 2 clutch kit with a single mass flywheel to go with it. I’ve done a ton of research so it all seems pretty straight forward. I know that I need to find a new rear diff to mach and use the front axels from the donor but I’m wondering if I can use the center diff and driveshaft from the donor as well. Any help would be greatly appreciated. Thanks

Btw I’m new to the forums and this is my first post so sorry if it’s not up to par.


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[Gosser]

I believe the B5 rear diff is much longer than the b6s, by what looks like 12”. You’d definitely need the prop shaft. I know the b5 prop shaft center bearing uses two large washers when mounted. B6s don’t have any washers. Someone out there must have tried it already.

First post seems to be on par.

[Gosser]

https://www.audizine.com/forum/showt...Swap-DIY/page3

That should help. Use the b6 axle flanges and the b6 rear tail to the transmission. There is no mention of proper shaft and rear diff, provided your rear diff gearing is the same.

[Gosser]

Also going from auto to manual, you will need a pilot bearing adapter. The automatic pilot bearing the crank is about 1” in diameter where the manuals are about 3/4”.

https://www.audizine.com/forum/showt...dapter-bushing

[Kevin C]

The rear diff ratio on your auto should be 4.11, the new tranny seems to be 3.89 so you will need to swap the rear diff. If you were to source a six speed from a 2004-2005 (GJW) the drive shaft and rear diff you currently have still work ( right length, same ratio) and you don't need to swap the rear diff.

[lean_wean]

Thanks for all the replies everyone. My current diff is 4.11:1 but I found another with 3.89:1 to match the gearing on the transmission and I’m getting the driveshaft with it. I’m definitely going to invest in that sweet new pilot bearing instead of the DIY method. Also I read on another swap thread that the center diff doesn’t have to be swapped out if you’re coming from the auto chassis. And I won’t be swapping the axel flanges in the front to b6 because the b5 2.8qm axels that I already have with the trans will fit from what others have said. I’ll post updates when I get all the parts and start the swap


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[Gosser]

Thanks for all the replies everyone. My current diff is 4.11:1 but I found another with 3.89:1 to match the gearing on the transmission and I’m getting the driveshaft with it. I’m definitely going to invest in that sweet new pilot bearing instead of the DIY method. Also I read on another swap thread that the center diff doesn’t have to be swapped out if you’re coming from the auto chassis. And I won’t be swapping the axel flanges in the front to b6 because the b5 2.8qm axels that I already have with the trans will fit from what others have said. I’ll post updates when I get all the parts and start the swap


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I dont think there ever is a center diff swap taking place. Where did you read that?

[lean_wean]

It’s the tail section of the transmission that can be bolted off and it connects to the driveshaft. I’ve seen people run a b6 center diff on a b5 transmission. I can’t remember what the thread was but I’ll try to find it.


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[Matt Devo]

It’s the tail section of the transmission that can be bolted off and it connects to the driveshaft. I’ve seen people run a b6 center diff on a b5 transmission. I can’t remember what the thread was but I’ll try to find it.

both the B5 and B6 5-speed tranmissions are 01A, and the center diffs are interchangeable. Late b5 and B6's use a 1-piece diff, older B5's use a 2-piece design, but they are functionally identical. It doesn't matter which you use, but you absolutely have to swap the tail housing from a B6 transmission in order to mount the Y-bracket for the transmission mount (which sits in the crossmember support)

[lean_wean]

Thanks for that info that’s kind of what I had thought. But instead of trying to find a b6 tail house I’m going to use the side mounts that are already on the transmission since it came out of a 2.8 a4. I may end up trying to find the tail housing later on so I’ll keep the cross member from the tip. But since I’m coming from a massive tiptronic to a 01A I can fit the side mounts on my chassis. If I had a manual transmission already than that wouldn’t work but in my case it does.


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[lean_wean]

https://www.audizine.com/forum/showt...Swap-DIY/page3

That should help. Use the b6 axle flanges and the b6 rear tail to the transmission. There is no mention of proper shaft and rear diff, provided your rear diff gearing is the same.

Do you know if any b6 axel flange will fit on the b5 01A? For example the ones of my tip.


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[wafi ahmed]

Do you know if any b6 axel flange will fit on the b5 01A? For example the ones of my tip.


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Did you done the swap?

[A4SoftWalker]

both the B5 and B6 5-speed tranmissions are 01A, and the center diffs are interchangeable. Late b5 and B6's use a 1-piece diff, older B5's use a 2-piece design, but they are functionally identical. It doesn't matter which you use, but you absolutely have to swap the tail housing from a B6 transmission in order to mount the Y-bracket for the transmission mount (which sits in the crossmember support)

Unless you intend to go with a Stasis or JHM 4:1 center-diff option for 40/60 torque split.

[AudiA4_20T]

Yeah I think the confusion here is you don't need the diff, you need the rear section for the 3rd mounting bolt on the crossmember.

[wafi ahmed]

I wish I can swap my in the future I love my b6 1.8t so much but I can’t put too much power because it’s tiptronic

[lean_wean]

Okay so I’ve been really busy lately but I ended up taking the parts and cars to my mechanic friend to have him do all the heavy lifting and shit I didn’t want to deal with. I’m picking it up tomorrow morning and I just need to do a little wiring, install my new pedal cluster and finish programming everything. But for the most part it’s been pretty straight forward. I’ll update when I make more progress and put up a complete parts list Incase anybody is wondering what worked for this swap.


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[lean_wean]

Unless you intend to go with a Stasis or JHM 4:1 center-diff option for 40/60 torque split.

I wish I had looked into that before. I’d love to drive a Quattro with a 40/60 split. Maybe I’ll do it later


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[Luis Alonso]

Yo estoy reemplazando mi multitronic por una manual de 5 velocidades, pero no puedo codificar la ecu