Rear clunking noise
Thread Starter
1st Gear
Joined: May 2009
Posts: 1
Likes: 0
Rear clunking noise
So I had the vette (76' L48 auto) out this weekend for a nice long drive. At the very end of the drive, while pulling into my complex, I got on the brakes really hard. I was greeted by a loud clunking noise and vibration. At first it sounded like it was only coming from the rear driver side wheel. After getting the car up on stands today, I put the car in neutral and tried rotating the rear wheels. The rear wheels are very stubborn to turn in one spot, to hard to turn with my strength atleast. I then put the car in drive and let the engine turn the wheels. Turns out, both the driver and pass side rear wheels are lifting about an inch and dropping during rotation, while simultaneously making a loud clunk. The pass side is doing this with about twice the frequency of the driver side. The rear end didnt make a peep before this. Did I bend something out of shape? I took the wheels off and everything looks okay visually (to my untrained eyes). I'll take a harder look when I have more time, but do these symptoms sound familiar to anybody who has experienced this before?
Drifting
Joined: Apr 2006
Posts: 1,911
Likes: 2
From: gold coast queensland
first off never jack your car up and turn your wheels with the engine. the reason your tires are bouncing up and down is cause your u-joints and half shafts are beyond their designed angles.this will happen when you do this. you will kill your uni,s in no time doing this and will bend something.. doing it by hand is fine.
now a clunk to me sounds like trailing arm bushes . 1 or 2 are shot . they will clunk when breaking hard or accelerating hard. you also mentioned a vibration and the fact your wheels will not rotate by hand free. time to inspect all 6 uni joints and both wheel bearings. uni joints normally click for a while before breaking and wheel bearings tick,then grind,then smoke,then squeel,then vibrate through your steering wheel,then fall off .
now a clunk to me sounds like trailing arm bushes . 1 or 2 are shot . they will clunk when breaking hard or accelerating hard. you also mentioned a vibration and the fact your wheels will not rotate by hand free. time to inspect all 6 uni joints and both wheel bearings. uni joints normally click for a while before breaking and wheel bearings tick,then grind,then smoke,then squeel,then vibrate through your steering wheel,then fall off .
Last edited by gingerbreadman1977; Jul 1, 2009 at 09:56 PM.
Former Vendor
Joined: Aug 2006
Posts: 76,656
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From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
Keltracer:
Better listen to Gingerbread! If you put the jack stands under the frame on the rear you will over extend and the J-joints will bind up. If you are going to check this put the jack stand under the trailing arm.
Once you do this then rotate the wheels and see where your noise might be.
Now depending on how you drove the car in the complex, did you make a sharp turn right before you came in. I’m going out on a limb here and guessing you did make a hard turn and your clunking noise is the posi unit locked up.
If I’m right when you make sharp turns the car will duck waddle around the turns. This can most often be cured by changing the fluid in the rear and adding an extra bottle of the posi additive. Once you change the fluid go to a parking lot and turn some circles. The clutches will either free up or they won’t. I’ll bet if this is the problem it will remedy itself if the fluid is changed.
If I’m wrong, I would check (again as Gingerbread told you) the front bushings on the trailing arms, the wheel bearing run out, the J-joints, the rear end snubber cushion and so on.
What made me go to the rear end was the statement you felt a vibration!
Check the car and post back.
Willcox Inc.
Better listen to Gingerbread! If you put the jack stands under the frame on the rear you will over extend and the J-joints will bind up. If you are going to check this put the jack stand under the trailing arm.
Once you do this then rotate the wheels and see where your noise might be.
Now depending on how you drove the car in the complex, did you make a sharp turn right before you came in. I’m going out on a limb here and guessing you did make a hard turn and your clunking noise is the posi unit locked up.
If I’m right when you make sharp turns the car will duck waddle around the turns. This can most often be cured by changing the fluid in the rear and adding an extra bottle of the posi additive. Once you change the fluid go to a parking lot and turn some circles. The clutches will either free up or they won’t. I’ll bet if this is the problem it will remedy itself if the fluid is changed.
If I’m wrong, I would check (again as Gingerbread told you) the front bushings on the trailing arms, the wheel bearing run out, the J-joints, the rear end snubber cushion and so on.
What made me go to the rear end was the statement you felt a vibration!
Check the car and post back.
Willcox Inc.
Instructor
Joined: Aug 2008
Posts: 104
Likes: 1
From: Warner Robins Georgia
to what Wilcox said. I had the same thing in my 74. I changed the diferential fluid, the stuff looked like it had been in there since the car was built, and went to a parking lot and did some circles... about 8 each way... really fun and made me a little dizzy. 
While your under there, drill and tap a drain plug.
