TS6

iTrader: (41)

I'm getting ready to order a 12 bolt for my 2002 Z28, which has run high 10's on a 125 shot, 127 mph. It currently has a stock rear with 3.23 gears, and its an A4 car. I do have a big stall, and H/C, as well as the usual bolt ons. Would a gear change do anything for me, and what ratio? This is mainly a street car, so no monster 4.30 gears for me. I was thinking maybe 3.73 or so.

Also, if I did the rear swap with a new gear ratio, could I even drive the car or would it need tuned immediately? I plan to have a custom tune done, but I will probably have to drive it a short distance. Thanks for the help!

TS6

iTrader: (41)

Help?

30th t/a

iTrader: (51)

3:73'S would be perfect i think especially with a auto and you have nitrous.....4:10s suck with a auto. i dont think you will need a new tune. changing the gears doesnt effect the motor. you will just need to recalibrate for the new gears.

TS6

iTrader: (41)

Thats what I'm saying, will it even run without recalibration? Whats the easiest way to recalibrate? LS1 edit or what?

30th t/a

iTrader: (51)

haha...yes it will run. your speedo will be off. you can use ls1 edit, hp tuners or you can send your pcm to any of the sponsors and have them adjust it or drive it to the place and they can do it right there. its no big deal.

2MuchRiceMakesMeSick

What size tires do you plan on running?

Sandmann120

iTrader: (1)

3.73s. Yes, it will run, but your speedo will be off, your ABS and ASR will likely throw a fit, and your trans shift tables will be off. But, it should be fine for a SHORT while. Also, are you set on a 12 bolt? You might also look into a 9 inch. Just a thought. Good luck.

TS6

iTrader: (41)

I plan to run 26" tires, but I'm also wondering if they will be tall enough with a 3.73 gear or if 28"s will be required. I have an A4, and the cars been 10.85 on a 125 shot, 127 mph. I know on my GN I had to run 28's because I'd run out of gear and have to shift into OD which sucks. Will 28's even fit a 2002 Z28? The 26's are on now and they look awful close to the rear bumper cover as it is, I can't see 28's going on without body mods.

I'm not set on the 12 bolt, I plan to order my rear next week and will be getting it from Billingsley racing, since they are 45 mins. from me. I plan to talk to Jay about what rear and what gear is best.

30th t/a

iTrader: (51)

26" tire@6500, 1:1 drive, 3:73's you can go 134.8mph
everything the same except a 6000 redline your at 124.4 mph
everything the same except a 6700 redline your at 138.9mph

now remember when you have a stall convertor and your at top end, i dont think it 100% locks up and theres usually a 3% slippage so figure if yoru redline is 6500, 134mph * .97 (3% slippage) your actual mph is 129.98mph.

Ragtop 99

iTrader: (7)

I'd up the converter slip factor to at least 5%. Not many converters slip that little running NA, and with a 125 shot the slip is likely to increase. Also allow for the fact that you'll be at WOT crossing the stripe so your final MPH may be a tad higher than the measured trap speed.