1971 rear end

[Phil A.]

What tourque should the pinion nut have after replacing the pinion seal? Should the pinion seal have about 045 clearance with the case? Thanks Phil

[Duke W.]

Re: 1971 rear end

There is no torque spec for the nut. When assembling the axle the nut must be tightened until a specific drag torque to rotate the drive pinion is achieved. There is a spec for both new and used bearings in the COM, and you need a 25 or no greater than 50 inch-pound torque wrench to measure drag torque.

When only replacing the pinion seal, carefully mark the orientation of the end of the drive pinion, nut, and companion flange prior to loosening the nut. Then after installing the new seal replace the companion flange using the marks to clock it with the drive pinon as originally installed. Then tighten the nut until its mark is aligns with the other two.

You should also use a sealer on the splines.

I believe the seal seats against a "step" in the bore, but I'm not sure. It's been too long since I overhauled an axle.

Duke

[Gary R.]

Re: 1971 rear end

Phil
As Duke mentions you need to measure drag, unless you are installing a solid sleeve but I doubt that. Here is a link I started years ago on replacing a pinion seal that will help you. There is a referenced gap between the seal and housing but I no longer use that. I measure the seal and the bore depth. I have found some bores vary and even had a few shallow bore where the seal would hit the flange. I had to either rebore the housing or remove the seal flange.

http://www.digitalcorvettes.com/forums/showthread.php?t=76719

[Steve G.]

Re: 1971 rear end

To properly reinstall the pinion you should always replace the crush sleeve and draw it down until the torque to turn the pinion is achieved, as described above. If you don't have a new crush sleeve you can simply make a thin shim out of sheet stock to effectively "lengthen" the crush sleeve.

The problem with making reference points and reassembling back to those reference points is that it deals with only one of two critical issues. One is the preload on the bearings which you measure with your inch lb torque wrench. Going back to your reference points will re-establish that.

But the other issue is the tension against the nut which is what prevents it from coming loose. In a diff where you adjust preload with fixed thickness shims, after determining your shim requirements you torque the nut to a spec. Two settings. Shim thickness for preload and torque on the nut to keep it tight.

With a crush sleeve arrangement, instead of having to determine the thhickness of the shim you need you crush the sleeve until the distance between the two bearings creates the correct preload. A one way adjustable shim if you will. Additionally, the crush sleeve has been designed so that the amount of torque it takes to crush the sleeve is also the correct torque to keep the nut from backing off.

So when you return it to a reference mark, you may have the preload right, but because you haven't crushed the sleeve any further you do not have the correct tension on the nut. And if you tighten further to achieve that correct tension on the nut you will crush the sleeve further and have too much preload. Adding a thin shim will allow you to tighten further and achieve both correct settings.

I have seen lots of pinion nuts come loose in my time, from exactly this.

As to the seal, you should look at the yoke. If there is a groove worn where the seal has been riding don't drive the new seal in all the way. Leave it out 1/16" so that the seal lip is riding in an unworn spot on the yoke.

Steve

[Steve G.]

Re: 1971 rear end

I should add this. Gluing the nut on the threads with a thread lock (Loctite) is not a suitable substitute for the tension created by the crush of the sleeve because the tension that holds the nut from backing off is also what keeps the inner race of the front bearing from turning on the shaft.

Steve

[Phil A.]

Re: 1971 rear end

Steve, thanks for the reply. Do you know if anyone sells differential stands or kits to attach to engine stands in order to work on the differential?

[Phil A.]

Re: 1971 rear end

Thanks Duke

[Phil A.]

Re: 1971 rear end

Gary, thanks for the reply, it is very educational. Do you have the differential attached directly to the engine stand with two bolts? Thanks Phil

[Steve G.]

Re: 1971 rear end

Phil, the ones we had were the big C shaped ones. They had a pipe swivel, but the receptacle bolted to the bench top. It would probably fit in an engine stand. They were made by Kent-Moore or OTC, one of the big outfits that supplied tools to the dealerships. Very pricey. I've never seen them from a Harbour Freight kind of store.

Steve

[Gary R.]

Re: 1971 rear end

Gary, thanks for the reply, it is very educational. Do you have the differential attached directly to the engine stand with two bolts? Thanks Phil

yes a 63-79 vette diff will mount to any engine stand using 3/8-16 bolts. The only exception is the 63 Grand Sport diff, one of which I rebuilt several months ago.

What is your plan, is the diff out of the car now?