Visit The Dirt Forum for More Information

Author Topic:   gears and rpm
Oldsmobile13
Member
posted June 12, 2001 04:06 PM
what gear are you running in? do you have to run that big of a tire we have been running a 3.08 in second gear for years with a 205/70/14 comes out to be 82 in tire roll and i drop to a 78 in roll when i run on a 4/10 mile useuly run about 6500rpm going in to the corners hope this helps


49mtmod
Member
posted June 13, 2001 08:32 AM
First, if you are running 5500 rpm and want to be running 7000 you are not geared too low, you are geared too high. The higher the gear number numerically, the lower the gear.

Also, I assume your are running in 2nd gear. If so, you need to find out what the second gear ratio is in the tranny. For example if you are running a saginaw with a 1.68 2nd gear, you would be running a 4.62 final (1.68 X 2.75). In that case, both the 3.00 (504 final) and the 5.14s would help. If it is a 1.89 second gear you would be running a 5.19 final. The 3.00 (5.67 final) would still help but the 5.14s would be going the wrong direction.


Oldsmobile13
Member
posted June 13, 2001 11:01 AM
I have a simular question. i am running a ford with a 400 mod.with a FMX tranny 9" 2.75 gears i need to know what type of older vehicle came with 3.73 gears so i can change.


racer17j
Member
posted June 15, 2001 01:05 AM
i don't think they made a 373 in 9 in just 7.5 and 8.8 you would have to go with a 370 or 389... 373 is a gm gear i belives . i do know i've never seen one for a 9 in in any of my mags anyway


4s racing
Member
posted June 15, 2001 08:02 AM
thanks racer17j i got my sheet out and they are showing 3.7,3.75,3.82,and 3.89. i guess i been around the bow tie people to long LOL.is there any way to find what the ratio is without tearing the rearend apart.and counting gear teeth?i have acess to numerous rearends but don't want to tear them all down. what would be the ratio of 1.25to1.0 of the wheel. is there a formula that you kow of? any help would be great.


49mtmod
Member
posted June 15, 2001 08:39 AM
A quick way to get an estimate of what gear ratio is in a rearend is to mark the pinion and then spin the tire/wheel 1 full rotation and count how many times the pinion turns. If the gears are 3.89s one rotation of the wheel should give you 3.89 rotations of the pinion.


4s racing
Member
posted June 15, 2001 10:23 PM
thank you 49mtmod you just made my day. I have been arguing with a freind of mine for 2 days that is what you can do.he kept telling me the only way was to tear it down and count ring teeth and pinion teeth. Then again he is a COON *** .LOL. but he is a good freind.


chevythunder93
Member
posted June 16, 2001 12:10 PM
what is the gear ratio in a turbo 200?


racer17j
Member
posted June 16, 2001 09:10 PM
same as a t350 but it's a time bomb 2.72 1st 1.52 2nd 1 drive


Back to the Archives