72 c10 pinion nut torque specs?

[mike16]

Replacing the yoke and pinion seal on my 72 c10 axle.

What is the torque specification on the pinion nut.

Any other advice?

Thank you.

[Mike C]

There is no pinion nut spec. The 12 bolt is assembled with a crush sleeve and it is torqued to a specific rotating resistance measured in inch pounds.

I have found that when replacing a yoke or seal, if you just tighten it as tight as you can get it with a standard 1/2” ratchet, that will get it done.

If you tighten too much you change the preload on the bearings. I recommend you replace the pinion nut when you do this as the locking ability of the nut is reduced after use.

[super72swb]

I have watched several how to videos and you torque to 25 in lbs of drag while rotating the yoke… please do your research research

[mike16]

Thanks for the advice. I did research and got essentially three different answers.

[ullose272]

Originally Posted by super72swb

I have watched several how to videos and you torque to 25 in lbs of drag while rotating the yoke… please do your research research

thats really not even correct, pinion bearing preload is set without a diff carrier installed, and is different with new vs used bearings. rotating the diff, axles, ect will show a high rotational resistance but actually not have enough on the pinion bearing.

What Mike C said will get you in the ball park, you wont be able to get it perfect without disassebly

[WorldsCrappiestTruck]

Above is right. Pinion only, no carrier, tighten the bejeezus out of it until you get rotational drag (or a torque reading on a dial or bar type torque wrench).

To do this for me, I put a pair of 1/4” extensions into the holes on the yoke that hold the ujoint straps, then trigged a bar between them and over to the trailing arm, so as I tightened the nut, the apparatus would keep the pinion from turning.

From there I had a 2-foot 1/2” breaker bar, then the handle of my jack shoved over the breaker bar to properly crush the sleeve - probably 4-5’ of leverage. It takes a lot.

[MikeB]

Here's the procedure I learned from a hotrodder who worked as a Ford mechanic for over 30 years, and now has his own shop working on hot rods and muscle cars:

When replacing a pinion seal, get the rear wheels off the ground, remove the driveshaft, and then measure how much torque it takes to turn the pinion. Go ahead and replace the seal, reinstall the yoke, and then tighten the nut, checking pre-load frequently. Once it's the same as you measured in the first step, you're done.

This won't be as accurate as doing it with the carrier removed, but pre-load is now back to where it had been for any number of miles. Also, he recommends re-using the old nut, and using thread locker on it.

[ZEKE68]

13-15 in-lbs for new bearings and 6-7 in-lbs for used bearings, while rotating the pinion, with no carrier in place. This is for 12 bolt truck rearend. I have marked the nut, and replaced the seal, then retightened the nut to the mark, maybe just a hair past, before without problems.

[MikeB]

Originally Posted by ZEKE68

I have marked the nut, and replaced the seal, then retightened the nut to the mark, maybe just a hair past, before without problems.

Sounds like a good way to go.

[volksworld]

think the magic question is how many ft lbs does it take to cause the collar to crush...as long as you stayed under that number you wouldn't alter the preload...tried to ask a buddy that built rears what that number was and his reply was something along the lines of ''you have to tighten the f**k out of them"....thanks...

[LS short box]

So on my hot rods with GM 10/12 bolts the local rear end builder hasn't used crush sleeves for years. He uses shims to get the correct pre-load. He says it makes changing out the pinion seal if needed is so much easier.

[MikeB]

Originally Posted by volksworld

think the magic question is how many ft lbs does it take to cause the collar to crush...as long as you stayed under that number you wouldn't alter the preload...

Probably true, if you knew what that number was. But simply measuring the pinion bearing preload before disassembling means you don't have to care about how much torque it took to compress the crush sleeve when the rear end was set up.

I've done a few crush sleeves, but couldn't tell you what the numbers were because I didn't have a torque wrench that would show over 250 lb/ft. All I cared about was crushing the sleeve to the point where I had the proper pinion bearing preload. However, I'd guess it was 250-300 lb/ft.