clunking noise from the rear

[wipeout]

Hello all,

Just wondering if someone can help me, when i put my 77 vette into drive sometimes it makes a clunking noise in the rear end (differential).

Also if I am driving and let go of the gas pedal it will sometimes make a clunking noise. I can sort of feel it, almost like I ran over a rock or something.

Any help would be great.

thx

 

[wookiebear]

Universal Joints

Sounds like you might have to replace your universal joints, there are 6 of them 2 on each half shaft and 2 on the drive shaft. You can order them through Ecklers.

 

[klb76]

;stupid I also think it is the U-joints, having mine replaced this week for the same reason...

klb

 

[vetteboy79]

Differential mounting bushing?

There is a fat, thick bushing about 2 inches in diameter where the rear differential carrier mounts to a crossmember in the middle of the frame. If this bushing goes, the differential will have a lot of front-to-back play in it. Depending on the deterioration of the bushings, you can end up with a metal-hitting-metal situation whenever the power transfer changes direction. Eckler's sells a whole new bushing assembly for this, and you can also obtain some of the parts through any chevy dealer. I had a similar problem in my '79, and I'm currently in the process of replacing this so I'll let you know how it goes. Best of luck with it -

Chris

 

[78SilvAnniv]

The rear yokes...

...I think that is what vetteboy79 is talking about.

We had to replace mine about 7 years ago. I was going through u-joints like crazy, and then my rear tires (inside) were getting chewed up!
Wound up replacing the rear end at the same time. (78 had been through a flooded stream)
Have had no problems with the u-joints since then.

The noise my rear end was making with the rear yokes was more of a grinding, groaning, moaning sound when first rolling out of a stop and also going around slow corners.

The clunking I think, is just the u-joints, but you may wish to check the yokes. I think you lift the rear up in the air and try to push-pull at 12 and 6 and 9 and 3 o'clock. If you have a lot of play or noise, the yokes could be the culprit.

*My advice is from memory of other posts, please perform a search to find the proper method if someone does not chime in with the correct procedure.
Heidi

 

[wicky88s1975]

I get a solid klunk only when I put it in reverse. granted reverse is only used to get it out of the drive but the noise is bothersome. any suggestions? I had the tranny serviced recently and the klunk was there before. the 75 is in the air right now (doing suspension rebuild) I'll check all the things already mentioned.

 

[wipeout]

ok guys,

gonna go check the u joints ill let you know what i find out.

But what should I be looking for, do I pull on them to see if there loose. Or will they look broken or rotted out or something.

 

[ChuckG]

When I check U joints, I do 2 things.

First...visual. Look for rust/flakes, etc around all 4 "legs" of each U joint.

Second...roational. Put the car up in the air. I take a long screwdriver to use as a pry bar. I push it up in between the U joint and the driveshaft/halfshaft. I'll then "hold" the U joint with the screwdriver while I rotate/turn the rear wheels/driveshaft. I observe for movement/clunks. Reposition the screwdriver to hold the other "half" and check that too. If you've got movement WITHIN the joint, it needs to be replaced. Under each of the 4 caps on each U joint are MANY little roller pins. Those rust and deteoriorate. Chuck