Pinion Torque spec
Thread Starter
Le Mans Master
Joined: Aug 2000
Posts: 7,484
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From: POTSDAM NY/Punta Gorda FL
Pinion Torque spec
I am changeing rear ends, and had to replace the pinion seal, does anyone know the torque specs, they are not in the Chassis service manual that I can see.
Tom M
Tom M
Safety Car
Joined: Mar 2001
Posts: 4,359
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From: AUSTIN Tx
There is no torque spec for the pinion nut. You just tighten the nut to crush the crush sleeve until the preload on the pinion bearing is correct. There should be a spec in the manual for the force necessary to turn the pinion in the bearings, for both new and used bearings. Keep in mind that these specs are for only the pinion bearings and not the carrier as well. I will tell you that I have never checked the rotational force in my life. I just tighten the nut until the pinion bearing has just a light drag on it and then stop. I do not even have a torque wrench capable of reading low enough to check it. You would need a torque wrench that goes down to 10 in/lbs or less.
Regards, John McGraw
Race Director
Joined: Nov 2000
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From: Beverly Hills (Pine Ridge) Florida
1st method (which is too late now), is to return the pinion nut to the same exact position that it was in prior to removal.
Optional method (which is also too late) is to measure the pinion torque (to turn the whole pinion/ring gear/axles/wheels & tires) while the rear is off the ground. Then tighten the nut back to where the pinion rotating torque is at the same point as before.
By using the above optional method, if you loosen the pinion nut (say 1/2 turn), and then take the rotating torque reading, you could then re-tighten it back so that it does not exceed that initial reading by any significant amount. I would then add a small amount of additional torque (to the loosened reading), just so I was assured that the nut was tightened. Do not confuse the rotating torque reading (the amount of torque needed to rotate the assembly) with the amount of torque needed to tighten the nut (which will be much higher).
Note that since the torque reading (when rotating the whole assembly) will be higher than when rotating via the spec setting of just the pinion, the actual rotating torque reading will be well within the range of the typical 3/8" torque wrench.
Good luck,
Plasticman
Optional method (which is also too late) is to measure the pinion torque (to turn the whole pinion/ring gear/axles/wheels & tires) while the rear is off the ground. Then tighten the nut back to where the pinion rotating torque is at the same point as before.
By using the above optional method, if you loosen the pinion nut (say 1/2 turn), and then take the rotating torque reading, you could then re-tighten it back so that it does not exceed that initial reading by any significant amount. I would then add a small amount of additional torque (to the loosened reading), just so I was assured that the nut was tightened. Do not confuse the rotating torque reading (the amount of torque needed to rotate the assembly) with the amount of torque needed to tighten the nut (which will be much higher).
Note that since the torque reading (when rotating the whole assembly) will be higher than when rotating via the spec setting of just the pinion, the actual rotating torque reading will be well within the range of the typical 3/8" torque wrench.
Good luck,
Plasticman
Last edited by Plasticman; Jun 27, 2007 at 08:26 AM.
Tech Contributor
Joined: Aug 1999
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From: Connecticut, USA
new bearings are 18-20 in/lbs used about 5in/lbs. Be careful not to over crush the sleeve when reinstalling.
If you PM me I'll link you with a full pictorial I have on this job.
If you PM me I'll link you with a full pictorial I have on this job.
Advanced
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From: Maumee OH
You mentioned a link to a pictorial on this. Could you send it to me at ajmcmaster@buckeye-express.com?
Advanced
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From: Wyomissing,Pa.,USA
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Melting Slicks
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From: Pasco Florida
More important, read the threads above to understand how this nut is to be installed. There's a lot more to it.
Race Director
Joined: Apr 2015
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From: Fresno California
You most likely need a new nut. Originally, these nuts had what is called prevailing torque. That means it's a self locking nut with distorted upper threads. If it has ever been removed with an impact wrench, the self locking feature is gone.
More important, read the threads above to understand how this nut is to be installed. There's a lot more to it.
More important, read the threads above to understand how this nut is to be installed. There's a lot more to it.
Tech Contributor
Joined: Aug 1999
Posts: 15,187
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From: Connecticut, USA
Speaking of working on vette diff's. I was looking at youtube today during lunch break. There are some newer vette diff builds posted, if you follow what I saw I will guarantee the diff is not going to work too good. The one a saw today had some spec's posted up - completely wrong information. good luck
Race Director
Joined: Mar 2018
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From: Golden Colorado
What.....
False information on the Internet? I'm shocked!🙄 As for pinion bearing preload (that's what we're dealing with here). There is only one way to set it correctly. Many people have many different ways of doing it and some occasionally work but there are pitfalls. GM built a differential that in most cases lasted 100,000 miles. To do it the right way there should be a new crush sleeve put in anytime preload is lost. The pinion nut which is torque prevailing should always be replaced also. I know you can lock tight it, add more crush on sleeve, etc. Not the GM recommended way. With a new crush sleeve and seal installed the new nut is tightened until the sleeve begins to crush setting preload on the bearing. Be careful it takes a lot of torque to crush it but once it starts to give it goes quickly. The proper amount of preload is measured in rotating torque of the pinion with an inch lb dial type torque wrench. The measure is rotating not what it takes to start it turning but what it takes to keep it rotating. Of course this is all done without the ring gear / carrier installed. The measurement is different for new or used bearings and they should be well oiled with gear oil for measurement. That is the correct way to do it. Not looking to start an argument just stating a fact. Again I know a lot of people do it a lot of different ways but this is the procedure by the book. Good Luck
Melting Slicks
Joined: Jan 2007
Posts: 2,842
Likes: 622
From: Pasco Florida
False information on the Internet? I'm shocked!🙄 As for pinion bearing preload (that's what we're dealing with here). There is only one way to set it correctly. Many people have many different ways of doing it and some occasionally work but there are pitfalls. GM built a differential that in most cases lasted 100,000 miles. To do it the right way there should be a new crush sleeve put in anytime preload is lost. The pinion nut which is torque prevailing should always be replaced also. I know you can lock tight it, add more crush on sleeve, etc. Not the GM recommended way. With a new crush sleeve and seal installed the new nut is tightened until the sleeve begins to crush setting preload on the bearing. Be careful it takes a lot of torque to crush it but once it starts to give it goes quickly. The proper amount of preload is measured in rotating torque of the pinion with an inch lb dial type torque wrench. The measure is rotating not what it takes to start it turning but what it takes to keep it rotating. Of course this is all done without the ring gear / carrier installed. The measurement is different for new or used bearings and they should be well oiled with gear oil for measurement. That is the correct way to do it. Not looking to start an argument just stating a fact. Again I know a lot of people do it a lot of different ways but this is the procedure by the book. Good Luck
Safety Car
Joined: May 2014
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So in service if the seal is changed the nut is marked for an approx reinstall location. If not marked or the nut replaced the best you can do is lock the yoke in place and sneak up on the nut location by tightening to where all in/out movement of the yoke is gone, correct?
Team Owner
Joined: Mar 2003
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From: Greenville, Indiana
A local Chevy mechanic used to pull the crush sleeve out and lightly hammer the crush in the sleeve to flatten it a tiny bit. Then, re-tighten the nut to get the riight drag.
Last edited by MikeM; Nov 3, 2018 at 11:15 AM.