rear end gears

[krazylunatic]

Is there anyway to tell what gears a rear end has without taking the cover off, maybe running the vin number or something somewhere? also im new to chevys but is a 12 bolt stronger then a 10?  im wanting some different gears and figured i might as well beef the whole rear end up

[Lt.Del]

RPO codes should be in you glove compartment...if you never replaced the glove comp.  RPO code will tell (via a code you can pull up on the internet) what the ratio is.

There is, according to some, a stamp on the axle tube --passenger side of hogs head on the tube facing the front...some kind of stamped/engraved ratio on that.

there is also the old fashioned way to approximate the rear ratio by jacking up the rear and marking a tire with chalk.  Turn the drive shaft and count how many times you turn it for each revolution of the tire. Divide the numbers together....driveshaft revolutions / rear wheel revolution. It should get you close to say 4.10, 3.73, 3.08, etc...

[Captkaos]

VIN won't tell the gear ratio.  If the cover hasn't ever been pulled and the oil replaced now is a good time.  The RPO is the only option, but keep in mind that someone may have changed it.  That is why it is only guaranteed if you pull the cover.

[Irish_Alley]

like capt said the only sure way to know if you pop your cover but if you know your speed, rmps and tire size there is a formula you can use


if your running 50 mph @ 2k w/ 38" then
your ratio would be about 4.53
rpms x tire size / 336 / mph = ratio
2000 x   38    / 336 /  50    = 4.53

http://forum.73-87chevytrucks.com/smforum/index.php?topic=10879.0