1991 VW Jetta 8V...16V transmission?

Last fall, I converted my rust-free 1991 Jetta from an automatic to a manual transmission. I used a 1986 Jetta parts car. I also used all new, high-quality wear items (clutch, motor mounts, axles, etc) in an attempt to do it right the first time.

Recently, said 1991 Jetta has been popping out of reverse. I have a known-good 16V close ratio gearbox I can swap in, but I have a bunch of questions...

• Can I re-use my 8V clutch? It only has a few thousand miles on it.

• Can I re-use my 8V axles? They, too, only have a few thousand miles on them.

• Will the close ratio gearbox bring any other positive benefits, other than the good reverse gear? (better acceleration, etc)

The transmission in it now is an "ACN" code 1986 box with a 3.66:1 final drive.

Thanks!!

M030 wrote: - Can I re-use my 8V clutch? It only has a few thousand miles on it.

Yes and No. You can use the pressure plate. You will need a 16V clutch disc. The spline on the input shaft on the trans is different (16V trans shaft is larger / more splines) so you need the corresponding disc. Do a verification that you have the correct clutch disc by sliding it on the spline before you put it in the car. (I've learned this the hard way)

M030 wrote: - Can I re-use my 8V axles? They, too, only have a few thousand miles on them.

Yes. They are both 100mm flanges.

M030 wrote: - Will the close ratio gearbox bring any other positive benefits, other than the good reverse gear? (better acceleration, etc)

There's a gear ratio guide here that you can see how much different it'll end up being: http://scirocco.org/gears/ (there's a few errors, but it's mostly accurate)

Only other difference may be a different reverse light switch plug. Easy enough fix if needed.

Lastly, depending on how you use this car, you might consider swapping in your old ACN 5th gear into the 16V box (AGB/2Y) which will essentially make 5th a highway gear dropping from a .91 to a .75. I have done this on a mk2 I used to own... close ratio 1 through 4th for fun, I never hit 5th on trackdays anyways.. and the low 5th made for lower R's on the highway. Not much actual fuel mileage benefit, just less buzzing and wear/tear. The 5th gear swap is fairly easy, and only requires the nose cone pulled off and a little bit of homework. Write-ups can be found online.

It is the same friction disc. The pressure plate spec'ed for 16V cars is stronger, they are interchangeable.

No worries. As long as your car has 100mm inner CV joints your 16V trans will pop right in. Prepare to lose a lot of mileage on the freeway. Your close ratio box will be spinning the motor 3600rpm at 65.