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Author Topic:   final drive ratio ??
hobo
Dirt Roller

Total posts: 8
posted March 19, 2005 08:22 AM  
I am going into my second season racing. My question is i run a 77 pontiac with a 400 and a turbo 400 tranny, with 3.73 gears on a 1/4 mile banked track, with 205/70/15 tires what would my final drive be and what should it be? And do you think this is a good set up? Thanks

racer17j
Dirt Forum Champ
Total posts: 5390
posted March 19, 2005 09:15 AM  
I also would agree with 17j junk the 400 trans and goto a 350 turbo it also has a little higher 1st gear ratio to help get final drive a hair closer..or you could even go to a 200 metric trans lower 1st than the 350 but not as heavy of duty most people dont trust them but I ran one for 2.5 years with no problems

racer17j
Dirt Forum Champ
Total posts: 5390
posted March 19, 2005 03:11 PM  
we run a 1/4 mile track but are geared from 6.80- 7.20

also ran a big high banked 3/8 track running a 6.00- 6.33

with a 6.80 final i wasnt turning but 6,300

we have to use the asphault pull offs which are from 77-86 roll..

hobo
Dirt Roller

Total posts: 8
posted March 20, 2005 08:40 AM  
Thanks for all the info. Maybe next winters project will be to build up a T350. So far no problems with the 400. What is the formula for figuring out final drive ratio? and that equals your final RPM before corner? Also what are the tranny gear ratios for fist and 2nd. I think 3rd is 1:1. Also are the gears differnt from a T350 to a T400. Thanks again all.

racer17j
Dirt Forum Champ
Total posts: 5390
posted March 20, 2005 10:04 AM  
not to burst anyones bubble but maybe you should know that alot of drag racers use a t400 for the fact that it can put up with the abuse
and they don't use t350 because they cant handle the s***

just food for thought

racer17j
Dirt Forum Champ
Total posts: 5390
posted March 20, 2005 12:31 PM  
Let it be known that when you run any transmission in anything but high gear you are building more heat and you are gear breaking the car running it in 2nd gear. If you can put a nine inch in it and get the right gear to begin with run it in 1 to 1 and you dont have to worry about the bands or anything else taking a beating.

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