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73-87 Chevy _ GMC Trucks => Performance => Topic started by: krazylunatic on January 18, 2010, 02:48:14 pm
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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
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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...
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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.
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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
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