a couple weeks ago,i jacked the rear up & rotated one tire by hand,of course the other went the oposite direction,open rear which i suspected since i needed to tell john o. the ratio for my carb rebuild,i had my son mark the driveshaft,i rotated the right side & the driveshaft only turned 1 + rotation to my 1 tire rotation??wtf???did i find ANOTHER problem on this car?i couldnt find the stamping on the rear,but didnt spend forever looking either.i know damn well there is no such ratio :af:
-Perhaps you could try this method: the best way on a non-posi unit to check with no special tools is .... park the car on a flat surface. chock the front tires. put the car in nuetral. jack one rear tire off of the ground. place a jack stand under the car for safety. as you turn the tire exactly TWICE, carefully count the driveshaft revolutions . if you get just under 3 1/4 turns, the ratio will be 3.23-ish, a little over 3 1/4 will be a 3.31, a little over 3 will be a 3.08, a little under 3 will be 2.93, a little under 3 3/4 will be a 2.73 ... etc. etc. here is why you have to turn the tire twice ... with the other tire on the ground as you turn the tire thats in the air ... the spider gears in the rearend cut the driveshaft revs exactly in half. its like ... did you know that when you peel out with a car that only has one tire spinning that the spinning tire is turning TWICE as fast as the spedometer says (minus what little speed the other tire actually might be rolling). so if you are at a dead stop and you punch it and the speedo jumps to 60 mph and you havent started moving yet ... that tire is spinning 120mph .... no wonder it cant get any traction in those situations. __________________ er
Spinning axles & counting turns on well used rears to figure ratio has never been my thing. Typically, most rearends are not maintained well. While folks will change the oil in their vehicle's engines at somewhat regular intervals, r/e's are often left to run till a problem creeps up :spank: Wanting to figure out what ratio, nothing wrong with pulling the rear cover, draining the grease, & counting the teeth on the ring & pinion. A paint pen can be used to help keep track of the teeth. Simple division will get the ratio. While turning the pinion gear, one may run across problems like heavy rust pitting of the R & P, a loose pinion, or metal particles in the used gear oil. Many times, such a cursory look, can catch problems before they contribute to total failure. Loose pinions take out more r/p's than anything. Pre '70 GM bolt-in axle rears also have the pesky sealed axle bearings & should always be ck'ed. When done, swab out the housing, add fresh gear oil, & have the peace of mind that maintainance has been performed. Got posi? :3gears: Roger
GM part # and ring and pinion teeth count are usually stamped right in the head of the pinion. Should be easy to see with cover off. No need to count the teeth. Simply divide.
Copperhead is correct in respect to the ratio stamping on GM 8.5 gears. 8.5 GM 2.56 & 3.23 gears even have a machined 1/8" groove in the edge of the ring gear... real easy to spot :Brow: Many earlier GM gears, including many different GM 8.2 gears, have the ratio stamping on the back (flat machined side) of the ring gear, in that case, just easier to count teeth. Got posi? :3gears: Roger
