quick ? about rear gears my car 87 gta is supposed to have 3.27 gear but i am going through the traps at 6200-6300 @ 120 car has 26 in tires th400 off the shelf 10in converter 3500-3800 is this right seems a little high to me thanks for the help

 

6000 to 6500 good rpm for a sbc

 

https://www.thirdgen.org/calculations

I'm guessing 3.90 or 4.11, assuming you were in 1:1 when you crossed.

 

the motor is a mild bbc and the rear end is a 9bolt somethings not right

 

Sounds right to me for ratios I mentioned. Only way to know for sure is pull the cover and read stamp on ring gear. You probably could use a fluid change anyways.

 

went ahead and pulled cover and it does have 3.27's thanks for the suggestions

 

Sounds almost identical to the first couple of years I was running my car with a 383. 3.27 gears and running 12.0 at 118 mph. Went to a 4.10 gear and dropped into the mid 11's, maybe just under 11.5. When I went to a 28" tall tire, I jumped to 4.56 gears.

I ditched the 9 bolt when I did the deeper gear swap. 10 bolt gears are much easier to find.

 

my car runs 11.0s- 11.1s at 119 -120 ill just leave it the way it is till it breaks

 

11.0 with 3.27 gears is impressive. Just goes to show that you don't always need a deep gear to go fast but if you were geared for maximum 1/4 mile performance, the ET will get faster.

 

thanks i have put a lot of work in this dumb car i am going to give it a little nitrous next year and hopefully a 12 bolt