The clunking in the rear area of my 92 coupe has not gone away with the recent rebuild of the differential and replacement of all U-joints. The driveshaft was also rebalanced. The shocks are new the brakes are new. The clunk comes with any change in the forward to backward motion, whther it is shifting or just letting off the throttle. Any ideas? How about worn control arm bushings? They are original with 125k miles.

As an aside, my mileage and performance have SOTP improved since the diff rebuild and correction of the stuck clutch pack wherein.

 

Louis,
I have the same problem...I'm having the gear change clunk blues as well...have you checked the wheelbearings and such? I'm getting mine done in 3 weeks, first appointment I could get at Norris Motorsports, and I'm having the whole gambut done as well, with new shocks and headers in addition. Good luck, and keep us posted as to what you find!

 

Let me kniow if the wheel bearing fix corrects the problem.

 

Worn spindle control arm bushings (upper and lower that connect the knuckle to the frame right behind your seat) aren't technically a 'clunk'. :D They're more of a 'thump'. They sound like something hitting the inside of your (fiberglass) wheelwell, right behind your left ear if it's on the passenger side. Mine wasn't there on just basic forward/reverse, it happened when braking hard and when accelerating away from a stop hard enough to have engendered the first thump. ::::BRAKE:::thump! :::VROOOOM:::thump!

 

I've got a VERY similar problem with my 4+3 '87. There is definantly some sort of play somwhere in the drivetrain. If I'm at a stop, as I release the clutch, the drivetrain tightens up and clunks. If I stop accelerating (still in gear) and try to coast then it will clunk again (probably whatever it is going back to the opposite direction). If I then apply throttle to stop coasting it will clunk. Between shifts as I am releasing the clutch it will clunk. I am absolutely and positively baffled. Romeo Barrera and I just got done rebuilding the 4-speed only a few months ago and I had this problem before the rebuild. The tranny work did not seem to affect this problem one way or the other. During the rebuild we checked for play in the U-joints but did not find any.
My only idea is that it may be differential mounts but I do not know where those are hidden or what they look like :bb
This problem is worse sometimes than it is at other times... It really sucks when I'm traveling at slow speeds. There seems to be a certain point where it clunks back and forth at ~20mph in 3rd gear. It feels like something is clunking back and forth in there... it's beginning to drive me :crazy:

My e-mail is byocom@dork.com if anyone discovers what this mysterious clunk is then PLEASE inform me!

 

This mystery makes a regular appearance on the forum.
So far it seems to be that it is not year specific,independent of trans type and not really related to a particular milage.People have replaced various driveline components without any effect.I have the same problem on coasting to a stop.It feels like a worn out auto box dropping down a gear.I thought it was the O/d unit going so I had it rebuilt and relaced the driveshaft joints but it is still there.
One suggestion my gearbox man made was that it could be play on the splines where the half shaft yokes exit the case.
The plot thickens.


Silver 1987 Coupe, Z51,4+3
TB Bypass,no mufflers or air pump
short shift kit

 

Here's my 2 cents. I am 3/4 complete with a D36 to D44 conversion. I bought a complete '84 D44, brake-to-brake, torque arm, and driveshaft with lotsa dirt and grime on it so I assume lotsa miles. The u-joints and wheel bearings (hard parts) in the D44 looked great. The rubber bushings (soft parts) were shot. With the exception of the carrier bracket (connects the differential to the chassis) bushings they all had cracks, some had chunks missing, and 2 strut rod bushing bolts were pushed about 3/8" from center. Don't know how the owners kept it on the road. Musta thumped and bumped like a can of rocks. The original D36 under my '95 has 65k miles and was not quite as bad. No chunks missing but all bushings showed cracks and several were beginning to elongate. Also the 4 sway bar bushings were all very cracked.

I'm replacing them all with urethane bushings from Corvette Central. Eckler's, Mid America, etc. also carry the urethane replacements. I believe a rear end bushing kit is about $100 and a front bushing kit is about the same. Replacing these bushings is at best a full weekend job. The most difficult tasks are removing the rear spring without killing yourself (unless you have access to the special spring tensioner/detensioner tool) and removing some of the bolts (bet they are torqued to more than 200 ft-lbs. - the manuals are in my shop). After replacing the bushings, and reassemby, the rear will have to be re-aligned much like a front end - toe-in/out and camber. Look in the above catalogs for exploded drawings and photos of the parts.

Not sure of a test method to determine which bushings may be suspect. Someone else may chime in here. Probably the old bounce test. Have someone bounce the car up and down while you slide under and watch for abnormal movement at the bushing locations. Don't get so far under that your friend mashes you and don't use your 300 lb. friend who can crack your fender!

If your car thumps only when you are turning I'd bet posi unit problems. If it thumps when accelerating, braking, decelerating by down-shifting, and hitting potholes I'd bet soft parts. If it's only when you brake and not when you down-shift I'd bet wheel bearing(s) or loose brake caliper(s). Also, when I purchased my '95 a couple of years ago it had a rear thump under heavy acceleration and over bumps. It turned out to be a missing nut on one of the shocks. Got the original owner to knock $700 off the purchase so I could repair the rear end but cost me less than a buck for a Nyloc nut!

Good luck!

 

Thump, Clunk, Thump, Clunk :crazy: Who can tell the difference? It does not seem to have a metallic click or sharp component. Definitely a dull sound. It does not have the speed sensitive whine of a bearing noise either.
All those responding seem to describe a similar sound. I also thought the splines might be the problem and had new one put in. The old ones were not worn when disassembled! Even though that's the "official" fix in the GM shop manual.

So far the worn spindle control arms sound like the culprit since several different cars with different trans and diffs have the same problem. Has anyone replaced these puppies and had the sound go away?

 

I have new spindle control rods with new bushings sitting in my garage. I will try to get them installed Monday or Tuesday and report back next week.

I tried to get to them myself, but the bolt that holds them to the knuckle is torqued to 140 ft-lbf. I couldn't break it loose with my socket wrench (felt like I was going to push the car off the jackstands), and my torque wrenches were too long to fit in the wheelwell.

So I'm going to let a good mechanic I know have at them with an impact wrench.

One other clue to look for - the bracket that holds the control arms to the frame, inside the wheelwell. Look at them and see if the black powdercoat is chipping and flaking off of one of them but not the other.

 

Was reading these threads and wanted to pass along some of the corrosion problems around the bushings.When you go to take off a suspension part and it will not budge, theres a high chance its getting corrosion around the bolts.
My bushings were shot and I pulled every suspension part off the back of the car, and had to install the spindles in a bench vise and use a breaker bar and with all my strength, finally cracked them free.
My impact gun could not get them off,but I admit my air compressor could use a little more power.

They had that white rusty corrosion on them and when you press the bushings out, the corrosion is all around the bushings too.
The aluminum breaks down and leaves that white crap in there and it needs to be sanded out smooth with a die grinder roll etc.

Most of my time was spent CLEANING the suspension bushing holes and the bolt threads and nuts.I had to use a dust mask standing in front of a fan to keep the white powder that would fly out from sanding, it made a dust cloud!!!

Also,Just replacing U joints as well doesnt always help the clunks...you need to sand down the rust off the yokes on the rear end sides and the U joint straps themselves, and wire brush the yoke splines that go into the bearings themselves and coat them with anti sieze or anti corrosion compounds.
Most shops do not do this work..throwing new parts at the car that has rust and corrosion still sitting in there doesnt always solve the problems.
Which is why when some people spray WD40 or something o those parts, the noise goes away for a day or two.

Hope that helps a bit.

 

Thanks, Bill. When I put my U-joints back in, I scraped off the corrosion and liberaly coated them with antiseize. Can't wait to get the spindle control arms off and give them the same treatment.

 

I had almost the same problem with my 92. The noise was coming from the rear left side. I got some excellent
advice from the forum with a fix for the problem. This is what it turned out to be. Moisture gets in the hub and
spline housing causing rust to form and the torque from neutral to forward or reverse causes the spline to clunk into the
hub. I am not talking rust chunks either, there was only a trace of red dust. The cure was to remove the hub and clean both the spline and the housing,clean both and add a little grease to the spline. Noise was gone. I waited for two years for the problem
to either get worse or something to break and neither happened. Finally gave up and took the time to try this
and it worked. Hope this helps. Cost of the fix was minimal as I did the work myself. I had to buy a couple of
metric sockets other than that nothing. I have the procedure somewhere to do the repair if your interested.

 

Don't know about the rest of you but my clunk's not just a noise... it actually jars the car pretty durn good...

When I'm looking for that bushing around the diff like was mentioned, what exactly am I looking for? My clunk does not seem to be biased to the left nor the right...

 

With all these detectives chasing this clunk "bug", I hope it's squashed. Let's keep this thread open until this is solved :smash: .

Can someone put some thoughts around this: my '87 only clunks when I have the shift in D rather the [D]. No clunk in Overdrive. But when I'm in D,
and slow down (foot on brake) , when I get to about 14 mph, CLUNK. Slowly speeding up, same thing. It sounds like it's coming from the area of the spare tire.

Bob

 

Mine also jars the car. When I was checking the U-joint by hand I did notice a slight click coming from the hubs. I think I'll fix those first. BTW MAD has the control bushings on sale at $50 in urethane.

 

My 91 started the clunk in the right rear this weekend too. It's the same symptom as most, it clunks when starting from a stop and going either forward or reverse. This morning however, on the way to work I turned a corner to the right and heard a scraping sound instead of a clunk. Has anyone else had a scraping noise?

 

Is it a CLUNK or a loud metallic CLICK? The "click" sounds more like hitting two bricks together.

700R4 auto tranny's are notorious for "clunking" on the 2-1 downshift as you're coasting to a stop. Nothing is wrong in that case, they just do that.

If it's a CLICK, or series of CLICKs when changing direction or applying/letting off the throttle, then it's probably one of the rear wheel bearings like a few others have said earlier in this thread.
I replaced my left rear bearing because of this but it turns out all I had to do was clean the rust off the spindle and use some anti-sieze lube.




[Modified by Thud, 9:41 AM 10/2/2001]

 

I'm still a little new to Vettes, but from what I know about the RX-7, which also has an independent rear suspension and RWD... The clunk you all are describing sounds exactly like one I had when the front rubber mount on the differential broke. The nose of the diff was actually bumping the floorpan on acceleration and bumping back against what was left of the mount on deceleration.

One other similar problem with them (which I also encountered on mine) was more of a loud popping as if something was shifting on acceleration. The fix was to get under there and tighten all of the mounting points you could find in the rear suspension. The noise never returned.

Hope this helps at least some of you.

 

If it jars your car, check the bolts on the torque arm (??) that connects the Trans to the Differential. Mine was WAY loose and the car would jump ALOT. Tightened it and the jarring/jump is gone. Still have the thump though.

 

The jarring is slight and I wouldn't have noticed it if y'all hadn't mentioned it. The torque arm was severly torqued down when I put it back in---have the sore muscles to prove it. Do you put lithium grease on the splines like you would a bearing or do you sparingly coat with Anti-seize? I have both.

All the mounting points were secure and the diff cover to frame bushings looked very good; no cracks and precious little oxidation like they weren't OEM. Are the spline corrosion opinions winning out over the control arm bushing opinions?