My stock rb20det ran a 9.6 in the 1/8 with stock bald tires and SE wheels. I just got some 17/40/255 mustang wheels so now I am trying to fig. out the best diff. set-up for the 1/8 mile.

A) keep stock 4.01 rear and install a j30 diff into it.B) 95-96 j30 diff bolts right in if my research is right changing to a 3.96...C) newer q45 is like 3.86 i think but pain in but 5 bolts

What do you guys think is best set up? Any other diff's that can work? I plan to keep rb basicly stock.Keep in mine im only worried about 1/8 mile time since its only track around me.

Swap in LS1.

J/K...not sure where you're getting your numbers from but they're a little off.

Stock is 4.08/4.11

J30 will not offer any upgrade in acceleration terms at ~3.92. Neither will the Q45 diffs (~3.53 in the G50, ~3.69 in the Y33)

For better acceleration, you want to go the opposite way, 4.36 (180sx) or 4.63(Nissan Motorsports/certain Nissan trucks)

However, I would concentrate more on power at this point and a better 60'. 60' will make or break you and you can usually bet that knocking .1 second in the 60' will end up lowering your ET by .15-.20 seconds in the 1/4.

Since you're running the 1/8th though, a 4.36 or 4.63 should help you a decent amount...but you can also affect your gearing using a shorter tire...like a 24.5" slick.

I have a j30 diff but I think im swicthing over to a welded stock diff. Just like cnichols said the higher number gives you more acceleration. I wanna say thats a plus for drag racing.

i run z32 n/a diffw 4.08gears kazz 1.5 way lsd with 92 j30 5 bolt axles(alot beefier then the 6 bolt axles), i have yet to break these axles but i do im upgrading to the mazworx axles

i have all 3 of the ones cnichols just talked about...i have the z32 4.08 lsd....a 4.4 and a 4.63 from a exterra front diff...still putting the car together so im unsure how any of these are gonna run with the new set up