# gear ratio for 63 impala rear end



## 63 ss rider (Feb 16, 2005)

please lket me know if anyone knows thank you.


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## Custom Jim (Jul 6, 2004)

There are a few possibilites as to what it could be from the factory but who knows as it might have been changed at one point in it's life. The easiest way to find out what you have is to park it on level ground, chock the front tires so the car does not roll or move, jack up one rear tire off of the ground and put the car in nuetral. Mark a spot on the tire and the driveshaft for reference and then slowly spin the rear tire one revolution while seeing how many times the driveshaft rotates. 
If with one tire revolution it spins the driveshaft about 2 3/4's revolution the gears would be 2.73. If it spins a tad over 3 revolutions it's a 3.08. If it spins right about 3 1/2 times then it's a 3.55. A tad under 3 3/4 revolutions it's a 3.73 and a tad over 4 revolutions and it's a 4.11 ratio. A tad over 4 1/2 revolutions would be a 4.56 while a 5.13 ratio would have a tad over 5 driveshaft revolutions per one tire revolution.
If with one tire off of the ground and in nutral if the tire spins you have an open differential (peg leg/single tire burnout). If it doesn't spin then you have a positraction rear end. If it is a posi then both rear tires have to be off the ground to allow the rear tires to spin while you count the driveshaft revolutions. If it's an open rearend and both tires off the ground you can get the wrong information.
Jim


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## biggeazy-e (Feb 6, 2003)

> _Originally posted by Custom Jim_@Jul 3 2006, 12:37 PM~5708210
> *There are a few possibilites as to what it could be from the factory but who knows as it might have been changed at one point in it's life. The easiest way to find out what you have is to park it on level ground, chock the front tires so the car does not roll or move, jack up one rear tire off of the ground and put the car in nuetral. Mark a spot on the tire and the driveshaft for reference and then slowly spin the rear tire one revolution while seeing how many times the driveshaft rotates.
> If with one tire revolution it spins the driveshaft about 2 3/4's revolution the gears would be 2.73. If it spins a tad over 3 revolutions it's a 3.08. If it spins right about 3 1/2 times then it's a 3.55. A tad under 3 3/4 revolutions it's a 3.73 and a tad over 4 revolutions and it's a 4.11 ratio. A tad over 4 1/2 revolutions would be a 4.56 while a 5.13 ratio would have a tad over 5 driveshaft revolutions per one tire revolution.
> If with one tire off of the ground and in nutral if the tire spins you have an open differential (peg leg/single tire burnout). If it doesn't spin then you have a positraction rear end. If it is a posi then both rear tires have to be off the ground to allow the rear tires to spin while you count the driveshaft revolutions. If it's an open rearend and both tires off the ground you can get the wrong information.
> ...


good info.. :thumbsup:


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## Custom Jim (Jul 6, 2004)

> _Originally posted by biggeazy-e_@Jul 3 2006, 12:02 PM~5708660
> *good info.. :thumbsup:
> *


Thanks. I had a buddy years ago that would not tell anyone what gear he had in the back of his car and while it was up on jacks one night with him wrenching on it elsewhere I got underneath, spun the tire, and counted the driveshaft revolutions and found out he had 4.88 gears. He didn't know I checked out his car this close and later I asked him how he liked the 4.88's and he was shocked I knew he had those gears in there.

The way I explained it it's also a good way to verify things at a junk yard or a swap meet. Some guys will say it's one thing but it's really another. Also just because a housing might have a gear code in it does not mean that's what's in there. Goofy things happen with older cars.

Jim


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## biggeazy-e (Feb 6, 2003)

> _Originally posted by Custom Jim_@Jul 3 2006, 03:06 PM~5708979
> *Thanks. I had a buddy years ago that would not tell anyone what gear he had in the back of his car and while it was up on jacks one night with him wrenching on it elsewhere I got underneath, spun the tire, and counted the driveshaft revolutions and found out he had 4.88 gears. He didn't know I checked out his car this close and later I asked him how he liked the 4.88's and he was shocked I knew he had those gears in there.
> 
> The way I explained it it's also a good way to verify things at a junk yard or a swap meet. Some guys will say it's one thing but it's really another. Also just because a housing might have a gear code in it does not mean that's what's in there. Goofy things happen with older cars.
> ...


thats the method i used to find out what i had in my rear end.. i asked the same info on here a few times and got no answer, so i found a site with the same info as you posted... :thumbsup:


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