Motive 3.90 Gears? A4

[LSWONZ28]

I'm wanting to change gears in my '99 Z28 A4 the car currently has 3.23 gears and I'm kind of wanting 4.10's but I'm worried after I install them I am going to regret it...as looking around at the ThunderRacing website tonight and saw that they have a set of 3.90's for the Camaro's?!?!? Anybody else running them and if so how do you like'em?? Should I just go with 4.10s? I had 3.73's in my old Z28 auto but would like a little quicker acceleration with out adding a stall.

Not that it matters lol but the only mods on the car right now is SLP LM2 and K&N FIPK best time so far was 13.202 @ 105.1MPH with a 2.02 60'

[GA Country Boy]

You definitely need to change your differential if you plan on doing much drag racing, BUT if it is still going to be a 'daily driver' I think you will find 4:10's are a little too low especially if you do much highway driving. At 70mph you'll be turning 2533 RPM when you're currently turning about 1995 RPM, a 3:90 would be around 2411 RPM.
If you're going to the labor of a differential change it wont be much more to do the torque converter (labor wise), but it will make a big difference in your ET's.

[LSWONZ28]

I don't do a lot of interestate driving most of the time it's just on two lane roads that i typically run about 60mph on. I've got a friend thats going to come over and install the gears for me he works at a Chevy dealer here in town...So if he was to come over say like on a Wednesday night and I take it to the drag strip Friday night with out tunning the computer for the gears is the car going to shift right?