8 3/4 "clunking" sound

[JoeMack2]

I have a 68 Satellite with 440,727 and 8 3/4 3.55 sure grip. My concern is, that when the car up-shifts or down-shifts(from 1st to 2nd or 2nd to 1st) I hear a "clunk" sound coming from the rear of the car. It only happens when it shifts with my foot off the gas pedal(no load). It also seems as the car is driven(warms up) that the sound is not as bad.I'm assuming that the noise is coming from the rear. I bought the complete center section from Zimmer Gear a few years ago and it has less then 500 miles on it. I believe it's always done it but I can't be positive. I called Zimmer and the person I talked to, seems to think that the noise is not coming from the center section but possibly from the rear tires not having the same diameter(under inflated). Could this be possible? Everything in the rear suspension seems tight and secure. I have new MP XHD leaf springs and new spicer u-joints. Does anyone have any idea what might be happening and should I be concerned ? And as usual, thanks for any help or ideas.

Joe

[Duffys Ramcharger]

I think what that guy is talking about is the clutches in the rear end making the noise. Check the tire pressure, and make sure the tires are the same size, brand, and equal tread. Does it pull to one side if you're accelerating? On the Track-Lock in my truck, if the tire pressure is off by more than 3 psi, it has a definite pull to one side. As far as the noise, it could be the clutches engaging and disengaging.

[ben440brown]

That's normal! I had a '69 Dart with the 7 1/4 rear do that for 148,000 miles and wear out two transmissions and one slant six. The clunk results from the backlash in the rear gears. The specs for Chrysler rear gears calls for a lot of backlash compared to, say, a Ford 9-inch. if you can avoid the backout upshift, you won't hear it.

Ben

[Chargerchuck]

I go with Ben440Brown. Backlash will definitely give you that nice "clunk." Just to be on the safe side, you might want to take a look at your U joints.

[carguy]

Hey guys: I have a 67 Belvedere with the same problem.The car has 64,000 miles. It sat for a long time. Replaced the axle bearings, u-joints, new rear-end fuild. I was begining to think it was my trans. Thanks for the info....

[djswwg]

You can also try using a heavier weight diff lube than the usual 80w90. And or add some Lucas conditioner to the diff..............djs