Rear End Ratio

[mjgord51]

I would like to know if it is possible to take the rear end cover off and ID the gear ratio and where would any information be on it with out pulling it out, Thanks in advance.

[hamjet]

If its a 68 c-10 6 cyl. 3 speed manual originally, (as long as the rear end is stock) it should be a 3:73 gear ratio unless it had the optional 3:07 or 4:11 which would be on the spid. if you pull the rear cover and rotate the ring gear you will see numbers stamped on the edge of the ring gear like 31:8, (made up numbers) and divide them to give you the ratio.

[BLT gmc]

The info will be stamped on the edge of th ring gear. It should list the # of pinion teeth and ring gear teeth and build date info. Hammer is correct. If I remember correct mine is 11/41 which I believe is 3.73.
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[67 chevelle]

code is stamped on axil tube usually passenger side 3 or 4 inches from housing

[LockDoc]

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http://67-72chevytrucks.com/vboard/s...d.php?t=578793

Code locations posts #8 & #19....

LockDoc

[Taibo]

Originally Posted by 67 chevelle

code is stamped on axil tube usually passenger side 3 or 4 inches from housing

What does that housing stamp tell you about a 48 year old diff that has been through who knows how many owners?

It takes a bit longer to drop the cover but it's the only way to be sure what you have. 37/9 = 4.11!

[mjgord51]

Originally Posted by hamjet

If its a 68 c-10 6 cyl. 3 speed manual originally, (as long as the rear end is stock) it should be a 3:73 gear ratio unless it had the optional 3:07 or 4:11 which would be on the spid. if you pull the rear cover and rotate the ring gear you will see numbers stamped on the edge of the ring gear like 31:8, (made up numbers) and divide them to give you the ratio.

Can't read the SPID very good

Originally Posted by BLT gmc

The info will be stamped on the edge of th ring gear. It should list the # of pinion teeth and ring gear teeth and build date info. Hammer is correct. If I remember correct mine is 11/41 which I believe is 3.73.
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On the way to O'Reillys for a gasket & lube

Originally Posted by 67 chevelle

code is stamped on axil tube usually passenger side 3 or 4 inches from housing

Getting out the wire brush as we speak

Originally Posted by LockDoc

-
http://67-72chevytrucks.com/vboard/s...d.php?t=578793

Code locations posts #8 & #19....

LockDoc

Thanks for the Link, great info there

Originally Posted by mike16

you might b able to count the number of teeth on the ring gear and the pinion gear and devide them

also the ratio might be stamped on the ring gear but it wont be a ratio per se but the actual number of teeth on the ring gear and the number of teeth on the pinion gear.

or you could count the number of rotations of your drive shaft to make one wheel rotate 360 degrees.

Tried the tire rotation & drive line trick but always came up with only 2 & a 1/3 drive shaft rotations, this trick didn't work for me. Maybe mine is 2 to 1 gears now that's freeway gears, just need a real stout BB to pull it up the hills I need to clime all the time

Originally Posted by Taibo

What does that housing stamp tell you about a 48 year old diff that has been through who knows how many owners?

It takes a bit longer to drop the cover but it's the only way to be sure what you have. 37/9 = 4.11!

I will open it up & look for #'s on the ring gear

THANKS to all for the answer I needed, so glad don't have to pull the "pumpkin"

[mike16]

you might b able to count the number of teeth on the ring gear and the pinion gear and devide them

also the ratio might be stamped on the ring gear but it wont be a ratio per se but the actual number of teeth on the ring gear and the number of teeth on the pinion gear.

or you could count the number of rotations of your drive shaft to make one wheel rotate 360 degrees.

[hamjet]

<<<Tried the tire rotation & drive line trick but always came up with only 2 & a 1/3 drive shaft rotations, this trick didn't work for me. Maybe mine is 2 to 1 gears now that's freeway gears, just need a real stout BB to pull it up the hills I need to clime all the time>>> This method usually doesn't work with open rear end only with posi...

[mjgord51]

Originally Posted by hamjet

<<<Tried the tire rotation & drive line trick but always came up with only 2 & a 1/3 drive shaft rotations, this trick didn't work for me. Maybe mine is 2 to 1 gears now that's freeway gears, just need a real stout BB to pull it up the hills I need to clime all the time>>> This method usually doesn't work with open rear end only with posi...

Knew it wasn't a posi, one wheel went one way & the other the other way.

[LockDoc]

Originally Posted by hamjet

This method usually doesn't work with open rear end only with posi...

It will work with an open but you only jack up one wheel, not the whole rear end.
LockDoc

[mjgord51]

Originally Posted by LockDoc

It will work with an open but you only jack up one wheel, not the whole rear end.
LockDoc

The drive wheel (pass) or drivers side? I had jacked the hole thing up I guess that's why I couldn't get a good reading. Learn & let live!

[Stocker]

Originally Posted by mjgord51

The drive wheel (pass) or drivers side?

Either side -- as long as one tire is up & the other is on the ground, you're good to go.

[mjgord51]

Originally Posted by LockDoc

It will work with an open but you only jack up one wheel, not the whole rear end.
LockDoc

Thanks good to now know.

Originally Posted by Stocker

Either side -- as long as one tire is up & the other is on the ground, you're good to go.

Thanks good to know that

[mjgord51]

Originally Posted by LockDoc

It will work with an open but you only jack up one wheel, not the whole rear end.
LockDoc

Originally Posted by Stocker

Either side -- as long as one tire is up & the other is on the ground, you're good to go.

Hay LockDoc & Stocker guys, Guess what I only jacked up one wheel and let the other on the ground and got different readings, Not what I was hoping for here they are I marked the tire @ 6 o'clock and bottom of drive shaft and rotated tire in both ways and counted the rotation of drive shaft and did this 3 times and came up with same # of rotations it went around only 1 & 7/8 all most 2 rotations of drive shaft. STILL thinking it's a 2 to 1 rear end LOL LOL , Whats up Doc & Stocker man ???

[BLT gmc]

Because your center section is open or non- posi, you will need to rotate the tire two complete rotations while counting the number and fractions of rotation of the driveshaft to find the approximate ratio . In an open diff, when you hold one wheel solid the action of the spider gears will cause the non-solid wheel to travel at an increased rate. This is not the case in a locked diff or a properly functioning posi. In a posi you rotate the tires one revolution while counting the driveshaft rotations. This will give the ratio directly. Bruce
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[Stocker]

^^ What he said.... rotate the tire two times and count the approx. rotations of the driveshaft.


This link says the same thing, with a bit more detail: http://www.how-to-build-hotrods.com/gear-ratio.html

"If your car has an open rear, jack up only one rear tire and leave the other on the ground. Now put a jackstand under the lifted side. Turn the tire and again count the number of turns of the driveshaft, but this time you must turn the tire two full rotations.

So:

Posi: Jack both wheels off the ground. Turn one wheel 1 complete turn.

- Count the turns on the drive shaft.

Non-posi: Jack one wheel off the ground. Turn the wheel 2 complete turns.

- Count the turns on the drive shaft.

If it takes about 2 and three-quarters turns, it's around a 2.73 gear ratio. If it's a little more than 3, you have 3.08s. If it takes about 3 and a quarter turns of the driveshaft, you have 3.23 or 3.25 gears. Very close to 3 and three-quarter turns, 3.70 or 3.73 gears. This method won't work very well on a posi that's worn-out and won't spin both tires equally.

This method is very handy when looking through junkyards or swap meets. It's good to be able to figure what gear ratio you have without tearing anything apart.

This is a quick and easy way to tell what gear ratio is in your rearend. You might not be able to tell exactly what gear you have, but you'll be very close.

If you want to be accurate, then count the teeth."

[mjgord51]

Originally Posted by BLT gmc

Because your center section is open or non- posi, you will need to rotate the tire two complete rotations while counting the number and fractions of rotation of the driveshaft to find the approximate ratio . In an open diff, when you hold one wheel solid the action of the spider gears will cause the non-solid wheel to travel at an increased rate. This is not the case in a locked diff or a properly functioning posi. In a posi you rotate the tires one revolution while counting the driveshaft rotations. This will give the ratio directly. Bruce
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Originally Posted by Stocker

^^ What he said.... rotate the tire two times and count the approx. rotations of the driveshaft.
I was not told the tire needed to go around twice, Thanks.

This link says the same thing, with a bit more detail: http://www.how-to-build-hotrods.com/gear-ratio.html

"If your car has an open rear, jack up only one rear tire and leave the other on the ground. Now put a jackstand under the lifted side. Turn the tire and again count the number of turns of the driveshaft, but this time you must turn the tire two full rotations.

So:

Posi: Jack both wheels off the ground. Turn one wheel 1 complete turn.

- Count the turns on the drive shaft.

Non-posi: Jack one wheel off the ground. Turn the wheel 2 complete turns.

- Count the turns on the drive shaft.

If it takes about 2 and three-quarters turns, it's around a 2.73 gear ratio. If it's a little more than 3, you have 3.08s. If it takes about 3 and a quarter turns of the driveshaft, you have 3.23 or 3.25 gears. Very close to 3 and three-quarter turns, 3.70 or 3.73 gears. This method won't work very well on a posi that's worn-out and won't spin both tires equally.

This method is very handy when looking through junkyards or swap meets. It's good to be able to figure what gear ratio you have without tearing anything apart.

This is a quick and easy way to tell what gear ratio is in your rearend. You might not be able to tell exactly what gear you have, but you'll be very close.

If you want to be accurate, then count the teeth."

I was not told the tire had to go around twice. I'll give it one more try,Thanks

[BLT gmc]

This is a bit of key info and why Stocker and I mentioned it. Keep us posted.
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[mjgord51]

Originally Posted by BLT gmc

This is a bit of key info and why Stocker and I mentioned it. Keep us posted.
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first try was only one tire turn @ 1 7/8 turn of drive shaft so thinking two turns of tire will give me 2 X 1 7/8 turns = 3 3/4 turns of drive shaft. Being that is a 3.75 ish ratio RIGHT LOL all right for all you i & t dotters (.) & crossers (t) here 3.73 for the gear ratio. another LOL