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Discussion Starter · #1 ·
hi..im just starting at this whole building a muscle car thing. i have a 403 with a bit more then mild modifications to the motor. im wondering for good low end grunt, but not something that cant be taken out on the highway, what would be the best gear ratio to run in my final drive?

one more thing, what is the gearing i have in it now?

thanks alot..

1979 pontiac trans am
oldsmobile 403
auto
standard size tires..
 

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My posi is a modified 79 transam. It came with (are you sitting down) 2.41 gears. Im not sure if all TAs had that ratio I'd assume not. Best way to figure is to pull the cover and count gears.

My cousin just put 3.73s on his camaro and his highway RPMs are about 3K with 15 inch tires. 3.42s are the best street gear in my opinion.

If you count the gears and end up with a 2.xx number then you need a ring gear spacer to use 3.xx+ gears. of another carrier.
 

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If there is no tag under cover bolt indicating ratio.

Jack up one rear, parking brake off. Turn the one wheel by hand. A posi should give you lots of resistence or refuse to turn at all.

If little resistence do this:
If only one tire turns.. =open rear or posi shot....., make sure the other is completely stopped (on the floor). Put trans in neutral. Turn one tire 1/2 turn, counting driveshaft turns = gear ratio

If a posi do this =
Jack up both rear wheels, trans in neutral.
Mark the driveshaft and tire treads with chalk to be sure they turn the same amount.
Turn tires one full turn (both tires should turn the same if posi) and count the number of turns the driveshaft makes..... That is your gear ratio.
 

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Discussion Starter · #4 ·
ratios

alright but im still a bit confused about what would be the best for me..can you give me some ideas? like what ratio would be good for what?
highway
gas
low end
top end
thats kinda what im looking for..thanks alot!
 
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