AFC or 5N or 3U??

Wondering what may be the optimal 016 Getrag for my CAV mono. Rear tires are 295/50/15 with a rolling diamter of approx. 26.6 inches. With the currently installed AAZ she's turning about 3,150 on the freeway at 75mpg - exactly what Ron E's spreadsheet predicts (nice work Ron!).

I have a 5N and an AFC. The AFC has similar gearing in 1-4 as my current AAZ however the 5th gear ratio is much taller (.73) providing about 2,700 rpm at 75mph - about where I'd like it. The 5N gearing is slightly shorter in 1-2, about the same in 3-4 and taller in 5th though not as dramatically taller than the AFC.

For a price, I also have access to a 3U however this box seems too tall with a .64 fifth (that's 207mph at 6,500rpm). My car should max out at around 155 with the 302 SBF crate engine currently in her so gearing to 200+ seems silly.

Anyone have any experience with the AFC v. 5N v. 3U?

I realize some have used the 5N with a different r&P but want to leave that off the table here for discussion purposes for the moment.

Thanks!

Anyone have any experience or thoughts here? Would really love to hear about others experiences with these differing audi transaxles....

Thanks!

Seriously? Nobody have any hands on experience with different flavors of 016 in terms of playing with the ratios? Nobody installed an AFC in their car? Hhhmmmmm.....well, I guess I better take some pre- and post- notes and pics to share with folks here then....

Cliff

I recall Hershel's initial comments when he swapped in his 3U were favorable.
Dropped the highway RPM down to a reasonable level, which was important
given how many highway miles he racked up.

MikeD

I would say if you have the chance to get the 3U tranny you better get seeing as you can only get them from over seas unless they are imported i would think the 3U would be exelent for a good crate motor.

I am of the opinion that, for 016 boxes, you should get the tallest 5th gear ratio you can so you can keep highway rpms as low as possible.

Mark, I would agree if the scope of consideration didn't include matching peak hp with max speed. These cars are, after all, race cars for the street, so, coming up with a 5th gear ratio that allows for coordinating max revs & hp with max speed seems logical as well. In other words, too tall of a 5th gear will lower max attainable velocity by placing the engine revs too low in the range. And, trying to hit top speed in 4th won't be too productive.

There's a good compromise in there somewhere whereby highway rpm is reasonable (sub 3,000) but also not so tall geared that you can't get your gt40 over 150.