Rear diff clicking

[vetteboy79]

Hey everyone -

I just finished putting a new clutch, pressure plate, and clutch fork in my '79...it's never felt so nice! However, there seems to be a lot of commotion in the rear when going around turns. For any of you that also drive trucks, it feels like going around a corner when a part-time 4x4 system is used on dry roads. When starting from a dead stop in a straight line, everything feels solid. It's when I go around any sort of tight turn - slow or quick - that there's a bit of clicking and binding from the rear. Are these symptoms of low/bad diff fluid? I think next weekend I'll put it up on a lift and change it anyway, because I haven't done it since I've owned it...but I'd like to know if this might solve the problem, or if there's anything else i should consider while I have it up in the air. Thanks!

 

[Yoda]

Change the rearend Fluid with GM fluid and be SURE to put the GM posi-trac additive in, then take it out and make a few figure eights "8" in a parking lot..

If that doesn't take care of it we can go from there.

While in the air check the U-Joints and entire drive line. The rearend needs to be loaded to really check the bearings, but as a rule of thumb you can check for slop by grabbing the rear wheels at 12 and 6 o'clock and again at 3 and 9 o'clock and check for movement, excessive movement is a problem, but as I said it really should be done with the rear spring loaded. Also give the trailing arms a good visual inspection and the rear spring bushings.

Oh heck while I'm at it check the tire wear, and if you have time pull the tires and check the brakes, including the parking brake too.

Good Luck and Enjoy the

Bud

 

[page62]

My clunking was getting pretty bad. I did the fluid change as described by Rare81. It worked almost instantly!

 

[78SilvAnniv]

Try the fluid change first...

...but here is a horror story for you:

My 78 made a horrible moaning, groaning, binding noise as I went around corners at any speed, but mostly at slow speeds, and it was finally determined that my yokes were worn out.
My problem had been so severe that it necessitated changing out the rear end gears and side yokes along with the u-joints for added protection.

If you are able to do the fluid change with the GM additive (add that first before the regular fluid) you may be able to escape having to do more work to the rearend. Act quickly!

Good luck!
Heidi

 

[vetteboy79]

Thanks

I'll do the fluid change ASAP then...on a side note, the problem seems worse after the car has been driven for a while. After sitting overnight, it barely made any noise at all...then it got more noticeable as I drove it longer. Does this help the diagnosis at all?

 

[page62]

It was the same for me. Do the fluid change -- you have a better than even chance it will fix the problem!

 

[DDLS3]

vetteboy 79

What your hearing and feeling is most likely the clutches binding in the positrac differential when you take a corner. Bud has given you the reccomended procedure......it should resolve your problems.