I am a forum Newbie. I have been working on a wrecked '78 that I purchased many years ago and its now on the road and in the bug sorting stage. Its been a challenge all the way but the problem solving is one of the things I enjoy about the project. The front end was pretty much destroyed in the impact which was frontal toward the left side. Everything from the firewall forward including the frame is new, rebuilt, fabricated or from a donor car. The problem at hand is a differential that whines on accel., decel. and is quiet on float. There is new lube in it so I guess I am looking at a rebuild. Are there any tricks to removal or installation of the unit that will save time and knuckles? Advice will be appreciated.

If anyone needs some input on installing a front clip, it can be pretty much a one man (or a man and a boy) operation. Happy to help if I can.

 

Did you add some GM posi addative to the rear end? If not, get 2 bottles and add them, then go to a big parking lot and drive in slow figure 8's do about 15-20, reverse the direction and do them again.
If it still whines after that, you might be looking at a rebuild.

 

Gear whine doesn't have anything to do with the posi clutches. Worn gears or pinion bearings will result in the ring and pinion running at the wrong backlash and/or angle to one another, resulting in gear whine, especially under acceleration.

The good news is, if you're sure there's fluid in it (and it hasn't been run with low fluid in the past), it will likely run for many more thousands of miles. I don't remember who said it to me, but I remember being told that the old mechanic's trick for fixing diff whine was to turn up the radio! Mine was whining noticeably before I rebuilt it, and when I got them out, the gears were perfect.

Do a forum search, there are many threads on diff removal. I built a cradle that I bolted to my small trolley jack; I drilled holes in the rear cross piece of the cradle, then used stove bolts and wingnuts to fasten the diff to the cradle using the holes in the strut rod bracket:



This way it can't fall on you (120 lbs!) and it also allowed me to wheel the diff & crossmember right out into the driveway for a power wash. Makes installation really easy as well. If you find your gears need replacing, I recommend US Gears from Tom's Differentials, mine were easy to set up and have been whisper quiet

 

Thanks Rally68. That's a solution I can live with for a while. I don't have a radio to turn up loud so I guess I will have to install a louder exhaust system. Every problem has an upside.

The prevoius owner had some serious engines installed and I don't think that the diff had an easy life. My guess is that hard starts and possibly crash damage hasn't done the pinion bearings much good and gear alignment is less than perfect. The crash bent the frame and displaced the engine so some shock load must have found it's way rearward though the driveshaft. (Why am I rebuilding this thing? I didn't know any better.)

 

I've seen cars that had not been moved for many years with rust on the ring gear.

 

You don't have to remove everything like Rally68 did. You can just unbolt the diff from the rear end cover without disturbing the leaf spring or other suspension components.

Then make sure you don't find your posi case with a crack like this which will not manifest itself unless you spritz some brakekleen around the 2 windows.