Rear End Problem/Gear Decoding
Thread Starter
Registered User
Joined: May 2009
Posts: 1,452
Rear End Problem/Gear Decoding
Hi all. Been reading threadsfor a little while regarding rear end ratios and determining the ratios.
I found a good one where the directions were jack both rear wheels off the ground, rotate one tire 10 times, count the revolutions on driveshaft.
When I do that, I count approx 15 1/2 driveshaft revolutions. If I only have the passenger side wheel on the ground I count 16 1/4 revolutions for 10 tire revolutions. If 1 revolution, I get approx 1 3/4 revolutions. Does this make sense? When both wheels are up, I can hold the driveshaft in place when someone else turns the wheel. Is that supposed to work that way?
I know it's not a posi, as only the passenger side peels out when I nail it. I took the cover off a couple of years ago and counted the teeth, and a local club member deciphered it to be a 3.33 rear end, but that wasn't offered by olds. I'll be taking the cover off again, taking pictures and counting the teeth again.
Also, I think the pinion seal is leaking a little bit, and seeing I'll be draining the fluid and all anyway, I might as well pull the driveshaft and replace it. Is this the right part: http://www.autozone.com/autozone/par...=11964_0_5770_
IT doesn't say if it's for a 8.5 rear/ posi vs non posi, nothing. And the guys at AZ can't tell me anything... Advance Doesn't seem to even carry one.
I found a good one where the directions were jack both rear wheels off the ground, rotate one tire 10 times, count the revolutions on driveshaft.
When I do that, I count approx 15 1/2 driveshaft revolutions. If I only have the passenger side wheel on the ground I count 16 1/4 revolutions for 10 tire revolutions. If 1 revolution, I get approx 1 3/4 revolutions. Does this make sense? When both wheels are up, I can hold the driveshaft in place when someone else turns the wheel. Is that supposed to work that way?
I know it's not a posi, as only the passenger side peels out when I nail it. I took the cover off a couple of years ago and counted the teeth, and a local club member deciphered it to be a 3.33 rear end, but that wasn't offered by olds. I'll be taking the cover off again, taking pictures and counting the teeth again.
Also, I think the pinion seal is leaking a little bit, and seeing I'll be draining the fluid and all anyway, I might as well pull the driveshaft and replace it. Is this the right part: http://www.autozone.com/autozone/par...=11964_0_5770_
IT doesn't say if it's for a 8.5 rear/ posi vs non posi, nothing. And the guys at AZ can't tell me anything... Advance Doesn't seem to even carry one.
Last edited by jpc647; Aug 2, 2013 at 11:17 AM.
Randy C.
Joined: Feb 2009
Posts: 3,348
From: Albany, OR
What year of car are we talking about? Have you looked on the passenger side axle tube to see if you can find the two letter or letter-number code? Olds did make a 3.23 rear end, at least from 1965 through the 1972 model years.
Randy C.
Randy C.
Just an Olds Guy
Joined: Jul 2008
Posts: 24,528
From: Edmonton, AB. And "I am Can 'eh' jun - eh"
I looked on your profile and am guessing this is for your 72 Cutlass. Whoever told you 3.23's weren't available on Olds is blowing smoke at you. 3.23's were a popular gear offered on Cutlass line up for almost all models 64-77
3.23 ring gear has 42 teeth, pinion has 13.
The code Randy is talking about is located on the upper part of the axle just to the right side of the vent tube. It's a little difficult to get to, but if you do find it and the car has original gears, your axle code should be SR OXXX. The SR means 3.23 gears, O is Oldsmobile produced, and the XXX is the ordinal production date code of the day it was built. (mine matches exactly to the date the car rolled off the assembly line with a 2.73 open. It now has 3.42 posi so that axle code means nothing now) These letters and numbers are stamped, not cast, into the axle and sometimes they are hard to see if the axle has corrosion on it.
The oil seal looks right. Index your collar nut and count the number of turns to take it off. You'll need to put it back in exactly the same spot because of the crush sleeve on the pinion. You don't need to pull the driveshaft out all the way or you'll lose a lot of tranny fluid. Just undo the rear and move the shaft off to the side - the u joints will allow some play there.
When you get the seal out, clean the area really well. Add a small bit of RTV around the side of the oil seal before you install it. That will give a nice tight seal.
Make sure when you replace your pinion seal that you don't distort it by tapping on it directly with your hammer. Either press it in or put a large socket or washer on it and gently tap around the edges to seat it nicely. If you hammer on it directly or don't seat it evenly it will leak again.
3.23 ring gear has 42 teeth, pinion has 13.
The code Randy is talking about is located on the upper part of the axle just to the right side of the vent tube. It's a little difficult to get to, but if you do find it and the car has original gears, your axle code should be SR OXXX. The SR means 3.23 gears, O is Oldsmobile produced, and the XXX is the ordinal production date code of the day it was built. (mine matches exactly to the date the car rolled off the assembly line with a 2.73 open. It now has 3.42 posi so that axle code means nothing now) These letters and numbers are stamped, not cast, into the axle and sometimes they are hard to see if the axle has corrosion on it.
The oil seal looks right. Index your collar nut and count the number of turns to take it off. You'll need to put it back in exactly the same spot because of the crush sleeve on the pinion. You don't need to pull the driveshaft out all the way or you'll lose a lot of tranny fluid. Just undo the rear and move the shaft off to the side - the u joints will allow some play there.
When you get the seal out, clean the area really well. Add a small bit of RTV around the side of the oil seal before you install it. That will give a nice tight seal.
Make sure when you replace your pinion seal that you don't distort it by tapping on it directly with your hammer. Either press it in or put a large socket or washer on it and gently tap around the edges to seat it nicely. If you hammer on it directly or don't seat it evenly it will leak again.
Registered User
Joined: Dec 2011
Posts: 7,286
I found a good one where the directions were jack both rear wheels off the ground, rotate one tire 10 times, count the revolutions on driveshaft.
================
Almost.
Jack ONE tire up. Otherwise, as you found out, the OTHER tire always rotates a bit and throws your count off. And, since you are looking for 10 revolutions of the CARRIER, you need 20 tire revolutions. [you can also attain 20 tire revolutions in a posi rear end by rotating both rear tires (simultaneously, because of the posi connection) for 10 revolutions (each)].
Does this make sense? When both wheels are up, I can hold the driveshaft in place when someone else turns the wheel. Is that supposed to work that way?
=====================================
Yes
Here's how a differential works:
To get one CARRIER turn with one wheel stationary, you have to walk the spider gears around which requires TWO turns of the one movable wheel.
When I do that [jack both rear wheels off the ground], I count approx 15 1/2 driveshaft revolutions.
=============
One wheel moved while you were not looking.
If I only have the passenger side wheel on the ground I count 16 1/4 revolutions for 10 tire revolutions.
==============
Correct.
32.5 then for 20 tire spins = 10 carrier turns.
Divide everything by 10 and you get:
3.25 prop shaft turns for one carrier turn.
Closest factory ratio is 3.23:1, so that must be it.
If 1 revolution, I get approx 1 3/4 revolutions.
===========
Insufficient resolution with that method. 1.75 x 2 = 3.5, but the error is obviously +/- 0.3 or so.
[Whoever told you 3.23's weren't available on Olds is blowing smoke at you. 3.23's were a popular gear offered on Cutlass line up for almost all models 64-77
3.23 ring gear has 42 teeth, pinion has 13.
======================
There you go, just use the tooth count
It's stamped into the ring gear:
"blah blah blah 42 13 blah blah blah"
Take the obvious numbers, at least one of which is almost always a prime number, and divide them. Bob's your uncle, there's your ratio.
When you get the seal out, clean the area really well. Add a small bit of RTV around the side of the oil seal before you install it.
=============
Form-a-gasket #2 or Permatex Aviation goo 3H are also good choices. I think RTV is over-used. It's not the be-all and end-all of sealers. Opinions vary, however, and I respect the above poster's suggestion.
================
Almost.
Jack ONE tire up. Otherwise, as you found out, the OTHER tire always rotates a bit and throws your count off. And, since you are looking for 10 revolutions of the CARRIER, you need 20 tire revolutions. [you can also attain 20 tire revolutions in a posi rear end by rotating both rear tires (simultaneously, because of the posi connection) for 10 revolutions (each)].
Does this make sense? When both wheels are up, I can hold the driveshaft in place when someone else turns the wheel. Is that supposed to work that way?
=====================================
Yes
Here's how a differential works:
To get one CARRIER turn with one wheel stationary, you have to walk the spider gears around which requires TWO turns of the one movable wheel.
When I do that [jack both rear wheels off the ground], I count approx 15 1/2 driveshaft revolutions.
=============
One wheel moved while you were not looking.
If I only have the passenger side wheel on the ground I count 16 1/4 revolutions for 10 tire revolutions.
==============
Correct.
32.5 then for 20 tire spins = 10 carrier turns.
Divide everything by 10 and you get:
3.25 prop shaft turns for one carrier turn.
Closest factory ratio is 3.23:1, so that must be it.
If 1 revolution, I get approx 1 3/4 revolutions.
===========
Insufficient resolution with that method. 1.75 x 2 = 3.5, but the error is obviously +/- 0.3 or so.
[Whoever told you 3.23's weren't available on Olds is blowing smoke at you. 3.23's were a popular gear offered on Cutlass line up for almost all models 64-77
3.23 ring gear has 42 teeth, pinion has 13.
======================
There you go, just use the tooth count
It's stamped into the ring gear:
"blah blah blah 42 13 blah blah blah"
Take the obvious numbers, at least one of which is almost always a prime number, and divide them. Bob's your uncle, there's your ratio.
When you get the seal out, clean the area really well. Add a small bit of RTV around the side of the oil seal before you install it.
=============
Form-a-gasket #2 or Permatex Aviation goo 3H are also good choices. I think RTV is over-used. It's not the be-all and end-all of sealers. Opinions vary, however, and I respect the above poster's suggestion.
Thread Starter
Registered User
Joined: May 2009
Posts: 1,452
I looked on your profile and am guessing this is for your 72 Cutlass. Whoever told you 3.23's weren't available on Olds is blowing smoke at you. 3.23's were a popular gear offered on Cutlass line up for almost all models 64-77
3.23 ring gear has 42 teeth, pinion has 13.
The oil seal looks right. Index your collar nut and count the number of turns to take it off. You'll need to put it back in exactly the same spot because of the crush sleeve on the pinion. You don't need to pull the driveshaft out all the way or you'll lose a lot of tranny fluid. Just undo the rear and move the shaft off to the side - the u joints will allow some play there.
When you get the seal out, clean the area really well. Add a small bit of RTV around the side of the oil seal before you install it. That will give a nice tight seal.
Make sure when you replace your pinion seal that you don't distort it by tapping on it directly with your hammer. Either press it in or put a large socket or washer on it and gently tap around the edges to seat it nicely. If you hammer on it directly or don't seat it evenly it will leak again.
3.23 ring gear has 42 teeth, pinion has 13.
The oil seal looks right. Index your collar nut and count the number of turns to take it off. You'll need to put it back in exactly the same spot because of the crush sleeve on the pinion. You don't need to pull the driveshaft out all the way or you'll lose a lot of tranny fluid. Just undo the rear and move the shaft off to the side - the u joints will allow some play there.
When you get the seal out, clean the area really well. Add a small bit of RTV around the side of the oil seal before you install it. That will give a nice tight seal.
Make sure when you replace your pinion seal that you don't distort it by tapping on it directly with your hammer. Either press it in or put a large socket or washer on it and gently tap around the edges to seat it nicely. If you hammer on it directly or don't seat it evenly it will leak again.
I found a good one where the directions were jack both rear wheels off the ground, rotate one tire 10 times, count the revolutions on driveshaft.
================
Almost.
Jack ONE tire up. Otherwise, as you found out, the OTHER tire always rotates a bit and throws your count off. And, since you are looking for 10 revolutions of the CARRIER, you need 20 tire revolutions. [you can also attain 20 tire revolutions in a posi rear end by rotating both rear tires (simultaneously, because of the posi connection) for 10 revolutions (each)].
Does this make sense? When both wheels are up, I can hold the driveshaft in place when someone else turns the wheel. Is that supposed to work that way?
=====================================
To get one CARRIER turn with one wheel stationary, you have to walk the spider gears around which requires TWO turns of the one movable wheel.
When I do that [jack both rear wheels off the ground], I count approx 15 1/2 driveshaft revolutions.
=============
One wheel moved while you were not looking.
If I only have the passenger side wheel on the ground I count 16 1/4 revolutions for 10 tire revolutions.
==============
Correct.
32.5 then for 20 tire spins = 10 carrier turns.
Divide everything by 10 and you get:
3.25 prop shaft turns for one carrier turn.
Closest factory ratio is 3.23:1, so that must be it.
If 1 revolution, I get approx 1 3/4 revolutions.
===========
Insufficient resolution with that method. 1.75 x 2 = 3.5, but the error is obviously +/- 0.3 or so.
[Whoever told you 3.23's weren't available on Olds is blowing smoke at you. 3.23's were a popular gear offered on Cutlass line up for almost all models 64-77
3.23 ring gear has 42 teeth, pinion has 13.
======================
There you go, just use the tooth count
It's stamped into the ring gear:
"blah blah blah 42 13 blah blah blah"
Take the obvious numbers, at least one of which is almost always a prime number, and divide them. Bob's your uncle, there's your ratio.
When you get the seal out, clean the area really well. Add a small bit of RTV around the side of the oil seal before you install it.
=============
Form-a-gasket #2 or Permatex Aviation goo 3H are also good choices. I think RTV is over-used. It's not the be-all and end-all of sealers. Opinions vary, however, and I respect the above poster's suggestion.
================
Almost.
Jack ONE tire up. Otherwise, as you found out, the OTHER tire always rotates a bit and throws your count off. And, since you are looking for 10 revolutions of the CARRIER, you need 20 tire revolutions. [you can also attain 20 tire revolutions in a posi rear end by rotating both rear tires (simultaneously, because of the posi connection) for 10 revolutions (each)].
Does this make sense? When both wheels are up, I can hold the driveshaft in place when someone else turns the wheel. Is that supposed to work that way?
=====================================
To get one CARRIER turn with one wheel stationary, you have to walk the spider gears around which requires TWO turns of the one movable wheel.
When I do that [jack both rear wheels off the ground], I count approx 15 1/2 driveshaft revolutions.
=============
One wheel moved while you were not looking.
If I only have the passenger side wheel on the ground I count 16 1/4 revolutions for 10 tire revolutions.
==============
Correct.
32.5 then for 20 tire spins = 10 carrier turns.
Divide everything by 10 and you get:
3.25 prop shaft turns for one carrier turn.
Closest factory ratio is 3.23:1, so that must be it.
If 1 revolution, I get approx 1 3/4 revolutions.
===========
Insufficient resolution with that method. 1.75 x 2 = 3.5, but the error is obviously +/- 0.3 or so.
[Whoever told you 3.23's weren't available on Olds is blowing smoke at you. 3.23's were a popular gear offered on Cutlass line up for almost all models 64-77
3.23 ring gear has 42 teeth, pinion has 13.
======================
There you go, just use the tooth count
It's stamped into the ring gear:
"blah blah blah 42 13 blah blah blah"
Take the obvious numbers, at least one of which is almost always a prime number, and divide them. Bob's your uncle, there's your ratio.
When you get the seal out, clean the area really well. Add a small bit of RTV around the side of the oil seal before you install it.
=============
Form-a-gasket #2 or Permatex Aviation goo 3H are also good choices. I think RTV is over-used. It's not the be-all and end-all of sealers. Opinions vary, however, and I respect the above poster's suggestion.
Thanks for all the help. The videos were a nice demonstration.
Last edited by jpc647; Jul 29, 2013 at 12:50 PM. Reason: wthread
Just an Olds Guy
Joined: Jul 2008
Posts: 24,528
From: Edmonton, AB. And "I am Can 'eh' jun - eh"
You don't have to do anything other than take off the diff cover to see the ring gear. Then just turn it till you see the numbers stamped into the side facing you. Only down side is gear oil stinks - a lot.
Thread Starter
Registered User
Joined: May 2009
Posts: 1,452
Thanks all, now I just have to figure out this speedometer calibration thing...
Just an Olds Guy
Joined: Jul 2008
Posts: 24,528
From: Edmonton, AB. And "I am Can 'eh' jun - eh"
I know what you mean. I have a speedo gear adapter to put in my tranny since going from 2.73 to 3.42 will make the speedo useless without that.
Maybe Speedometer World can help you with your adapter? They have a toll free number. That's just one place I found on a quick web search. I'm sure there are others.
Maybe Speedometer World can help you with your adapter? They have a toll free number. That's just one place I found on a quick web search. I'm sure there are others.
Thread Starter
Registered User
Joined: May 2009
Posts: 1,452
I know what you mean. I have a speedo gear adapter to put in my tranny since going from 2.73 to 3.42 will make the speedo useless without that.
Maybe Speedometer World can help you with your adapter? They have a toll free number. That's just one place I found on a quick web search. I'm sure there are others.
Maybe Speedometer World can help you with your adapter? They have a toll free number. That's just one place I found on a quick web search. I'm sure there are others.
I talked to him, he told me he needs the teeth on another gear in the tranny. Sounded like he said drab or drav gear. Said it should have 8, 9, 10 teeth. Not sure what he's talking about. The drive gear has 18teeth, and the driven in the 30's or 40's..
Thread Starter
Registered User
Joined: May 2009
Posts: 1,452
bump. I just realized in my original post i typed 3.23 rear end gears but it was supposed to be 3.33. Typo.
I was told back when I counted the teeth(3 years ago) I had 3.33 gears in the rear, but I don't see 3.33's being available. I may end up having to take the cover off and count the teeth to be sure.
I was told back when I counted the teeth(3 years ago) I had 3.33 gears in the rear, but I don't see 3.33's being available. I may end up having to take the cover off and count the teeth to be sure.
Just an Olds Guy
Joined: Jul 2008
Posts: 24,528
From: Edmonton, AB. And "I am Can 'eh' jun - eh"
bump. I just realized in my original post i typed 3.23 rear end gears but it was supposed to be 3.33. Typo.
I was told back when I counted the teeth(3 years ago) I had 3.33 gears in the rear, but I don't see 3.33's being available. I may end up having to take the cover off and count the teeth to be sure.
I was told back when I counted the teeth(3 years ago) I had 3.33 gears in the rear, but I don't see 3.33's being available. I may end up having to take the cover off and count the teeth to be sure.
It will look similar to this, obviously these are not 3.23's.
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