i am doing a frame off restoration on my car....i pulled the companion flange and pinion nut off of the rear end to change the seal..THEN, a friend of mine says, "i hope you marked the position of the pinion nut so you can put it back exactly as it was" uhhhhhhhhhhh, of course i didn't!! does anyone know how important this is, and what i should do at this point to avoid problems in the future??? can i just torque the nut back on and go on? what should the torque be? help please!!! rick
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Re: differential pinion nut question???
Rick,
You may have gotten yourself into a bit of a spot on this one. There's really no accurate way to reset the pinion nut torque to spec's as there is no such specification. The actual torque requirements on this nut are determined by the amount of torque it takes to rotate the pinion in it's bearings. In other words, before the nut is tightened to remove all end play, there would be near zero torque required. As the nut seats the bearing rollers and applies some compression, the amount of torque necessary to rotate the pinion would start to increase. The specification, if I remember correctly, is something like 10 to 15 INCH pounds with new bearings and 5 INCH pounds with used bearings. (I'll look up the proper numbers) This measurement is to be done while rotating just the pinion and does not include the added torque required to also rotate the differential case and ring gear so the differential case must be removed. As the nut is being drawn down to seat, the rotational torque will quickly rise as the bearings seat and begin to create drag. The amount of additional rotation on the nut to increase drag from, say, 2 inch pounds to 25 inch pounds is probably only a few degrees of rotation so it's extremely easy to go too far. Not enough load and you will start to hear gear noise on deceleration. Too much and the pinion bearings will fail.
I know many will tell you that you can safely replace the nut with no problems but the problems caused by slightly over torqued pinion nuts won't show immediately. It may take hundreds or thousands of miles to cause bearing failure. I think that the GM service manual even has instructions for replacing the seal without disassembling the diff but this is risky if you have no experience with this.
If you have a GM overhaul manual, look for info in the differential section that describes the pinion bearing load/torque procedure. Let us know if you decide to reinstall the nut without disassembling the diff and we'll try to help you get it as close as possible. -
Re: differential pinion nut question???
GREAT!!!! now what? my intention is to put a new seal in, and replace the nut. the car only has 60k mi on it, and i had not intended to tear into the rear end. this is a frame off restoration, and the car prob won't be driven more than about 500mi a year, but i don't want to worry about rear end problems. would it be safe to snug down the nut slowly til i feel like it has seated into the bearings, and then go just a smidge more to get torque on it? much like installing wheel bearings? rickComment
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Re: differential pinion nut question???
That should work Rick, as long as you do it slowly and carefully. Thenut is a prevailing torque nut so it's difficult to tell exactly when it bottoms or makes contact with the bearing but if you go slowly, you'll know. You'll feel the difference in effort required. As soon as contact is made, make very small additions until you can JUST feel the slight difference in drag. If you happen to have an dial type inch pound torque wrench, you can check the total required to turn the assembly before tightening the nut so you have some idea of what to look for as you increase torque. If you can get it in the ball park, you'll be ok. Problems mostly arise when someone tightens the nut with an impact wrench and goes far beyond specs.Comment
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Re: differential pinion nut question???
thank you so much for your input.... i think i understand exactly what to do, and what NOT to do at this point! i will proceed cautiously, and THANKS AGAIN for your help...rickComment
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Re: differential pinion nut question???
make sure you put a small amount of non hardening perma tex on the all splines to make sure you do not have a leak there and also if you are using the same nut use red loc-tite on it.Comment
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Re: differential pinion nut question???
I hope everyone understands that there is a lesson to learn here: Always consult the applicable Corvette Shop Manual, (Chevrolet CSM and COM for post '65 models), AIM, and all other available documentation before you start taking stuff apart.
Anyone who works on their cars without having these documents, which are relatively inexpensive and readily available from many sources is foolish.
And, if you have them, you have to pull them out the read them. The knowledge won't hop into your brain when the books are sitting in a bookcase.
DukeComment
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Re: differential pinion nut question???
well.....i'm happy to provide a service, and set an example on how NOT to do something. hopefully all of us have now learned this valuable lesson via my experience.
i only wish we could all be more like DUKE, as he obviously has probably never made a mistake in his entire life! gosh, what a guy....Comment
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Re: three grove water pump pulley
I have rebuilt many rear ends and replaced I don't know how many rear seals and never had a Pinion bearing fail. Just tighten the pinion nut until it is snug rotate it a few times and see if you can snug it alittle more if not put 1/8 turn on nut and stake front of nut with a punch this will keep it from backing off. if you have a manuel and read about Pinion preload and Pinon depth they will talk about a crush sleeve this is what is used to set Pinion preload it takes over 200 FT Lbs of tork to start to crush this sleeve so you can see by tighting the Pinon nut the way I discribed will not crush the sleeve any more so your preload will not change. Use a new pinion nut I buy my rear end supplies from westcoast Differintial. I can't spell but I know how to set up rear ends.Comment
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Re: Be cool Rick
We ALL have earned the bragging rights to say "been there" and "done that" on one F-U-B-A-R project or another.
Welcome to the "OOPS" club Buddy!!
Most Coordially,
ChuckComment
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Re: three grove water pump pulley
Harold is right ! when I was a mechanic in my youth (Chevy) my specialty was rebuilding Trans and rear ends ( Corvettes).
Replacing the pinion seal or bearings, we simply used the air impact to remove and replace the nut . I held the impact for about three seconds that had 165psi then hit the pinion end with a 5lb hammer to set the crush sleeve and gain hit the nut again with the impact.
Remember they are roller bearing not ball bearings, and after years of doing it that way which old timers taught I never had a Corvette come back.Comment
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Re: differential pinion nut question???
thanks to everyone who offered advice on this subject! i really appreciate the input......rickComment
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