Pinion nut torque

[Chuck R.]

I was challenged to replace the pinion seal sooooo, per my handy shop manual marked the relative positions of the yoke, shaft and nut for ease of re-assembly.

In an earlier post I was concerned about how to start the nut as my trusty ole Craftsman breaker bar wasn't cutting the mustard. Well I finally placed a 3' pipe over the end of the breaker bar and finally the nut released.

Now that it's time to re-torque the nut, I attempted to pull the nut in with just the breaker bar but cannot get the nut back into proper alignment with the other marks.

NOW, my question is this, was the nut just corroded in place requiring the pipe on breaker bar setup to break it apart, or will I also need to use the pipe over bar method to once again hit the marks?

I fear over torqing the pinion crush collar or worse putting excessive strain on the gear assembly.

I was told about checking the torque required to spin the yoke as a re-assembly guide, but of course I found this out after it was apart!

Appreciate any "Been There" "Done That" wisdom

Feel like ole Bubba on this one ,

Chuck

[John M.]

Re: Pinion nut torque

Chuck,
I would pull on the nut just enough to line the original marks back up, regardless of whether I had to put a cheater bar on it. Obviously, there is no torque spec since it is whatever it takes to crush the sleeve. as long as you do not exceed the spec for rotating torque, then it should not be a problem.

Regards, John McGraw

[Clem Z.]

Re: Pinion nut torque

make sure to put "red loctite" on the threads when you reinstall the nut.

[Duke W.]

Re: Pinion nut torque

There is NO torque spec for the nut. You tighten it until the specified drive pinion bearing drag torque is achieved. This can only be measured with the axle out of the car during overhaul since drive pinion bearing drag torque can only be checked before the case/ring gear is installed.

That's why the service manual says to mark the nut position on the drive pinion so it can be installed at the same position, which should restore bearing drag torque if it was properly set when the axle was assembled.

Clem - I don't know about red Locktite. Won't that make it REAL tough to remove the nut in the future. Maybe blue Locktite would be a better choice.

Duke

[Clem Z.]

Re: Pinion nut torque

those nuts are self locking type and really should not be reused so i would use red to make sure it does not come loose. a air impac wrench will always get it off.

[Terry Leeker]

Re: Pinion nut torque

FYI Nearly all threadlock adhesives (except high temp) are made ineffective by heating to 250'F

[Chuck R.]

Re: Thanks for the help

Appreciate the input folks.

Was there a factory torque requirement that I might also be able to use as a backstop prior to my cranking down on the pinion nut?

Just curious.

Thanks again, this is great info,

Bubba Rice

[Duke W.]

No - bearing drag torque only *NM*

[Dave Suesz]

Pinion nut torque trick...

A friend of mine runs a very sucessful performance shop and for this repair on Ford rears (any year) he uses clean threads, a new nut, no threadlocker, and 125 foot-pounds. Works every time. Must be some similar torque for Chevys. Compare the nut sizes (all Fords use the same nut). I did this on my Mountaineer 6 months ago with no problems. I have been putting this off for a long time in my C1, but I have no choice because the 50 year old seal is leaking.

[Duke W.]

Re: Pinion nut torque trick...

"Must be some similar torque for Chevys"

Not there is not! When assembling the axle the pinion nut is tightened until the specified drive pinion bearing drag torque is achieved (without the case/ring gear installed). Look in any overhaul manual.

If the drive pinion nut has to be removed in the field, the procedure is to mark the angular location of the nut relative to the drive pinion and install it to the same location, or perhaps just a hair more.

How many times does this question have to be asked and answered in the same thread?!

Duke

[Mike M.]

What if you didn't mark it?

I'm just wondering here if you didn't mark the threads. Is there any way to install the nut without taking the rearend out of the car to arrive at the correct torque. Mike

[Duke W.]

Re: What if you didn't mark it?

If you didn't mark the nut/drive pinion relationship the LESSON LEARNED should be to procure the service and overhaul manuals and READ them before you bubba your car anymore.

Until advancing the nut closes up all the clearance between the pinion shim and front bearing you should be able to move the drive pinion fore and aft. Once the clearance is zero, you won't be able to move it and the torque required to further tighten the nut should dramatically increase, so gradually tighten the nut until all the clearance is taken up, then just a wee bit more, and hope for the best.

Duke

[Ralph Harlan]

Re: What if you didn't mark it?

I've followed this thread because I have no experience with failure from not having the torque precise, but no one has addressed the problems resulting from not having exactly the correct torque on the pinion nut. I've only had a few differential u-joint input flanges off (mostly from 4WD suburbans and blazers, and just "honked" them back down with a 30" piece of pipe on the ratchet - until recently when I replaced the pinion seal on my '97 Chev 1500 2WD truck. Some of these trucks have been driven for thousands of miles after the seal replacement. This time (with my '97) I followed the "Chilton" to the inch pound, but have only been about 3k miles so far. I do question the "inch pounds of torque required to turn the pinion shaft" (with the rear wheels free of the ground) before the removal of the nut/flange as being relative to the number of inch pounds required for the rotation of the pinion shaft upon reinstallation. Or - again by my "shop manual" returning the pinion nut to 3 - 6 ft/lb more than the torque required to free it at the start of the repair. Too many variables in both situations. And I was not able to get the nut quite back to the mark for the original position even with the "cheater".

So what is the result of not having quite enough - or slightly too much - torque? Gear whine? Rapid bearing failure? Major misalignment/binding of the gearset causing tooth breakage?

[Clem Z.]

Re: What if you didn't mark it?

without a lock on the pinion drive flange is is pretty hard to over torque the nut. we use a bar that bolted to the flange and rested against the frame to crush the sleeve so i do not think you can over torque the pinion nut just using the tires as a lock because of all the "spring" in the drive line. if i remember correctly it takes at least 250# to crush the spacer. like i posted before use "red loctite" to make sure the nut does not work loose because that is when the "trouble" starts.

[Chuck R.]

Re: It was all bench work

As the drive line is com-pletely out from under the car, the re-build process was the easy part, that darned nut was the bear.

But....now all is well on the Western Front as all pinion marks are re-aligned, the nut pulled in using RED loctite and the finished diff. is patiently waiting for the rest of it's associated attached components to join it.

Thanks again for the help Guys,

Chuck