Some questions about my rear end

[Randy Stockberger]

I'm in the process of rebuilding the rear suspension of a '70 300hp 350 coupe with a 4 speed. This is to be a 4K miles/year driver. I dropped the rear end and removed the cover to inspect the internals and it looks really good. The gear action is very smooth and there is no wear pattern at all on the ring gears. The car has about 100K miles on the odometer but I don't know it's history so that is probably a minimum figure. I know someone blew the rear end, I can see where they had the half shafts out, where one halfshaft is damaged underneath the U joint cap and the differential does not have any of the proper part numbers or stampings for a production corvette. Also, one of the rear wheel spindles has been reworked on a lathe - the threads were re-cut undersize.

My questions are:

* What checks should I do to the rear end? Since I can't see any wear I do not intend to get it rebuilt. * What gasket sealer, if any, should I use when I put the cover back on? * I intend to replace the side yoke seals, is it possible to replace the front (pinion?) seal without special tools?

Thanks Randy Stockberger, #32888

[Joe L.]

Re: Some questions about my rear end

Randy-----

Personally, I would not recommend putting the rear carrier back in the car without having it gone through and rebuilt. The fact that your ring and pinion gears look good just means that you probably won't have to replace them. This is good and, actually, is the case with most gear sets unless they've been seriously abused or improperly set up.

You still have such wear components as the posi-clutch pack and the differential carrier and pinion bearings to consider. At 100,000 miles, or more, these are probably well into their useful life.

Beyond all of that, it is difficult to properly replace the pinion seal without getting into the whole rear end. That's because the pinion bearing pre-load is set by a crush sleeve. Once crushed, the sleeve cannot be restored and to get into it and replace the crush sleeve requires disassembly of the unit. It is possible to do it without replacing the crush sleeve, but it's a tricky process and I certainly wouldn't recommend it for the inexperienced.

You should also carefully inspect the yoke axle ends for any wear. Even a little wear means that the case hardening has been "breached" and continuing wear will occur much faster.

[Randy Stockberger]

Re: Some questions about my rear end

Joe:

I don't think the rear end has anywhere near 100K on it since it doesn't show signs of wear and I know that it has been replaced. I'm reluctant to spend $500 on a rear end that doesn't need it when there are other places on the car that need the money, spending bucks on the rear end realistically means that I am going to postpone something else for 3 or 4 months. Also, since my labor is free I am willing to pull the differential again in a year or two if it starts to show signs of failure.

My current idea is to do whatever tests the board recommends and if things look good, put in new yoke seals, a new cover gasket and put it back in the car. I will not replace the pinion seal but will monitor it for leaks since I have neither the experience or tools to fool with it.

The yoke ends don't show any wear signs. there are no ridges from the previous seals, the splines are straight and crisp and the inner faces show the original tooling marks from the center out to the edges. The yokes slide in and out of the bearings and splines easily.

What should I use to seal the cover gasket? When I was a kid we just ran a bead of permatex around on both sides of the gasket. In addition to torquing it by the book do I: a) Use nothing except the gasket, b: Use Permatex 2B on both sides of the gasket, c: Use one of the silicon sealers?

Thanks - Randy Stockberger - #32888

[Joe L.]

Re: Some questions about my rear end

Randy-----

Yes, you might get away with not overhauling the rear end under the circumstances which you describe. However, other than the inspection points I mentioned, there are really no "tests" that I am aware of that you could perform to determine the condition of the assembly.

As far as the gasket goes, I use a GM gasket and apply a very light coating of chassis grease to the gasket prior to assembly. Then, torque to specs. Using this method, I've never had one leak.

[Randy Stockberger]

Re: Some questions about my rear end

Thanks Joe.

I'll cross my fingers and see what happens.

I've got some marine grease that I'll use to wet the metal surface of the rear end and the cover before I put it back together.

Once again, thanks

Randy Stockberger, #32888