A2 transmission questions

[larry104]

I have a '92 Ecodiesel with the original AVX trans. Top gear is a bit low for sustained highway cruise and I want to go taller.  My questions are, can I put a complete gear set from an 81-on FN trans into an AWY trans case? Apparently the AWY has 100 mm flanges and the FN, 90 mm. Will the FN flanges fit the AWY ouput shafts and my axles?  Is there a difference between 80-down and 81-on FN transmissions? I've rebuilt motorcycle transmissions before, but never a VW trans. I've read this and other forums about the many special tools required for the job. And I have a Bentley. Any pitfalls I should know about?  Thank you.

[Master ACiD]

is there any way that you could buy an fn trans and change the output flanges to be 100mm, or maybe change youre inner cv's to be 90mm and just use the fn trans? it seems like that would be alot easier, but i dont know if thats possible.

[larry104]

Does an 81-on FN trans fit a 92 Jetta? If so, it would save me a bunch of work. I was assuming this FN has different mounting brackets than my trans. Both transmissions have the same size flanges  -- 90 mm.

[addautomotive]

Swap out your 5th gear... this can be done without removing thh transmission from the car.

[larry104]

AVX has a 0.75 5th gear;  0.71 is the tallest 5th gear available, which won't improve things much with the 4.25 ring/pinion. The FN has a 3.89 ring/pinion and a .71 5th. I suppose I could just switch out the ring/pinion and 5th in the AVX, but I want to keep it stock and build another. Nice to know that you can switch 5th gears without dropping the trans.  Thanks.

[fspGTD]

A2 transmission mounting brackets use different mounting points on the transmission case than A1 transmission mounts.  The 020 transmission cases only have the holes for the A2 mounting brackets starting in 1984.  So when considering a transmission to swap to your A2, avoid any 1983 or earlier transmission.

[larry104]

Thank you.  A1/A2 trans cases aren't interchangeable. Do you know if the gears from A1 transmissions fit A2 housings?

[vwmike]

Thank you.  A1/A2 trans cases aren't interchangeable. Do you know if the gears from A1 transmissions fit A2 housings?

Generally yes, but there were some subtle differences over the years. You probably just want to use a wide ratio mk2 gear box. My Jetta has the 4S transmission and it seems to be geared pretty well. The 4.25 R&P that your car has is highly sought after. Whatever you do, don't throw out the trans if you don't use it.

[fspGTD]

Thank you.  A1/A2 trans cases aren't interchangeable. Do you know if the gears from A1 transmissions fit A2 housings?

Actually, 1984 model year A1 transmissions would work.  If you are in doubt, just look for the extra bolt holes on the transmission case.  Usually there is also a green-painted output flange seal cup on the passenger side output seal area of the 1984 and later cases also.

The 3rd, 4th, and 5th gears are interchangeable but the shafts (which have R&P, 1st and I think maybe 2nd gear attached) can only be exchanged if the have the same input shaft diameters.  Some later 020 transmissions and all the ones found on 16V engines use a larger input shaft diameter.  The case found on these is different to support a larger input shaft bearing and seal.

Changing the R&P pretty much entails complete disassembly of the transmission, so makes sense to rebuild it while you are in that deep.  If you are thinking about having a custom transmission rebuilt, I would contact Daryl of AA Transaxle.  www.aatransaxle.com  He is likely to have many parts on hand and can put together a custom tranny of your specs.  It would still probably be cheaper to just find a suitable good used donor transmission from either a wrecking yard or from private party, and swap it in.

PS - your 4.25 R&P is highly sought after in certain racing circles.  These folks want as high of a R&P ratio as they can find, and your transmission's R&P ratio is the highest (short of an expensive, aftermarket VW motorsport R&P.)

[larry104]

Thanks all for the great info!  I love this place.

fspGTD -- special thanks for the hook up on aatransaxle. I spoke with Daryl this afternoon.