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View Full Version : 3.73 or 3.90 gears for my A4?


BL96TA
07-10-2011, 04:09 PM
Thinking about getting some gears for my Trans Am, ive had 3.73 in the past with another LT1 A4 I use to have and liked them. However I was thinking of going with a little more gear this time. I was thinking of going with 3.90s. Would this be too much for daily driving? The reason I want the 3.90 is because I plan on running a 28' tall tire when i go to the drag strip, Ive even thought of going with 4.10s just to compensate for the hight of the tire I want to run. Thoughts?
joelster
07-10-2011, 04:20 PM
That's a good plan if you know you are going to step up in tire size. If you are making a serious drag effort with the car I hope you are talking about a new rear end though. The 10-bolt won't cut it at all. Also, I didn't know anyone even made 3.90's for a 10-bolt. Maybe they do now, who knows.
muddyjimmy
07-10-2011, 05:37 PM
Motive makes 3.90 gears for the 10 bolt. :secret:
BL96TA
07-11-2011, 01:50 PM
The 10 bolt will have to do for now but i do agree with what your sayings as far as upgrading the rear. I did see motive selling 3.90s on thunderracing.com for the 10bolt. In your opinion would I be better off with the 3.90 or 4.10? I plan on doing more daily driving than drag racing so I deffinately don't want to go too tall with the gears.
Dave357LT1
07-11-2011, 06:16 PM
I have 3.90's in my ten bolt. If its just boltons id do 3.73's. Ive seen bolton builds respond better in autos with them. Cam/heads step up the gear to 3.90 -4.xx to get it in the power band faster.
biggriff
07-11-2011, 06:27 PM
i have 4:10's in my bolt on A4...car runs mid 12's NA and mid 11's on a shot with a 1.66 60'...im on a 27" tire by the way...love the 4:10's...:claps:
Dave357LT1
07-11-2011, 06:53 PM
i have 4:10's in my bolt on A4...car runs mid 12's NA and mid 11's on a shot with a 1.66 60'...im on a 27" tire by the way...love the 4:10's...:claps:

Damn that is nice. What is ur race weight?
biggriff
07-11-2011, 07:22 PM
Damn that is nice. What is ur race weight?

almost full weight...just pulled a few things, front sway bars, exhaust (back end) and egr/smog stuff...She gets down the track...60's 1.7 NA on a "Pretty Much Stock" motor...thx
95formula383lt1
07-11-2011, 08:53 PM
David told ya ur car had more in it, 390s are fine in a bolt on car too. your shift points an a few other things i found on tear down was holding you back that an not enough passes as well as to much/a lot of converter for the set up.