Its a 1996 Z28 A4. It has 3.23 gears currently. I figure it would probably gain ~.2 in the 1/4 mile by swapping to 3.73. Is it really worth it? I figure I may lose a few MPG also. It will be mostly street driving also.

 

Depends on your other mods. If it can't make use of the extra RPMs, it's not going to help.

 

MUCH more fun to drive. I did this back in the day with a basically stock car and it was a blast.

 

A good converter would give you better gains, but then again the 3.73s make the converter easier to live with. So get both!!!!!

 

3k stall, 3.73 gears and some M/T drag radials on a completely stock set up will net you .3 to .5 depending on how bad your traction was to start with. That comparo is given that you are already getting 2.0 to 2.1 60' times. If your getting worse then even better. With the combo I stated on completely stock suspentions and engine/cam I was netting VERY consistent 1.80x 60' times back in the day. So yes 3.73 gears properly set up with stall and DR will help you a LOT. On street tires you'll prolly just roast the tires a lot more. FUN yes. Expensive yes. Does that help your times without the DR? Minimal gains to be had with stock cam.