Clunking sound.....
Thread Starter
Instructor
Joined: Mar 2006
Posts: 198
Likes: 0
From: Kentucky
Clunking sound.....
Just got my 78 back on the road from paint and interior work and there is a clunking sound in the rear on the driver side of the car when going around a right hand curve.
Just to be clear, the car has approximately 100k miles on it and has an automatic transmission. Never had any work on the rear except that I replaced the trailing arm bushings awhile back. It sounds to me as if the u-joint at the left rear wheel is where the noise is coming from and it sounds like a clicking sound. Could it be a bad u-joint? Wheel bearing? Any help on diagnosing this would be appreciated. I hate to just start replacing parts at random. Thanks, Paul
Just to be clear, the car has approximately 100k miles on it and has an automatic transmission. Never had any work on the rear except that I replaced the trailing arm bushings awhile back. It sounds to me as if the u-joint at the left rear wheel is where the noise is coming from and it sounds like a clicking sound. Could it be a bad u-joint? Wheel bearing? Any help on diagnosing this would be appreciated. I hate to just start replacing parts at random. Thanks, Paul
Last edited by pda1964; May 5, 2007 at 06:43 PM. Reason: Forgot to specify car is automatic!
Melting Slicks
Joined: Jan 2007
Posts: 2,589
Likes: 5
From: Salisbury Maryland
You should be able to isolate a u-joint problem by looking around and checking out the half shaft on that side. If the noise is still there when you push in the clutch, my guess is a wheel bearing, especially if it is more noticable turning in one direction.
I just finished replacing my passenger side bearing, it's not an easy job, but I was glad it wasn't the posi!
Good Luck, the people here will help you through it.
Grab the wheel at 12 & 6 o'clock, jacked up of course. How much movement do you have? If there a lot, it's probably the bearing. Clicking....hmmm, bearing I'd guess.
I just finished replacing my passenger side bearing, it's not an easy job, but I was glad it wasn't the posi!
Good Luck, the people here will help you through it.
Grab the wheel at 12 & 6 o'clock, jacked up of course. How much movement do you have? If there a lot, it's probably the bearing. Clicking....hmmm, bearing I'd guess.
Thread Starter
Instructor
Joined: Mar 2006
Posts: 198
Likes: 0
From: Kentucky
Update
I jacked up the car to perform the 3-9 and 12-6 tire wiggle test. Wiggling the tire from 3-9 didn't do much, it was pretty tight. However, the 12-6 did show some deflection at the trailing arm bushing point. Not as much pushing on the tire at the 6 but pushing at the 12 it was forcing the yoke deeper into the differential which I am assuming is the source of the noise. How much deflection is permissible at the bushing point? I was seeing maybe 1/4" back and forth into the yoke at the differential, but the twist of the trailing arm is what concerns me.
I had replaced the trailing arm bushings a while back and I remember there was rubber portion and a metal portion to the bushing and that you had to flare the metal portion. Does it sound like the bushing may not have been flared enough and the halves have separated?
Doesn't sound as if the bearings are the culprit unless I am missing something. I'd like to jump on this and fix whatever the problem is so I can drive the car so any feedback is appreciated.
Thanks, Paul
I had replaced the trailing arm bushings a while back and I remember there was rubber portion and a metal portion to the bushing and that you had to flare the metal portion. Does it sound like the bushing may not have been flared enough and the halves have separated?
Doesn't sound as if the bearings are the culprit unless I am missing something. I'd like to jump on this and fix whatever the problem is so I can drive the car so any feedback is appreciated.
Thanks, Paul
Drifting
Joined: May 2006
Posts: 1,480
Likes: 2
From: Circleville Ohio
Vader vette
Hey hope its this easy but have you added the rear end lube from the chevrolet dealer If not it kinda sounds like mine did before I used it This stuufff is not A joke it really works .The cluthhes dont slip as well without it, making a klunking .Just bought two bottles and A rear end seal.$8.oo per bottle and $5.oo for the seal.
Thread Starter
Instructor
Joined: Mar 2006
Posts: 198
Likes: 0
From: Kentucky
Removed Trailing Arm
Lon, Thanks for the tip. I did use the posi additive a few years back for a large clunking sound that I had a while back. It did the trick for that noise, but this is a different type of sound kind of a ratching/clicking sound from the driver side. Imagine that annoying noise when you are still rolling and have put the transmission in park. (BTW, I didn't do that, my sister did it once while I was in the car with her.)
But here is my status so far....I have removed the trailing arm on the driver side rear.
The bushing halves have not separated.
The wheel bearing feels smooth backwards and forward with no spots where it catches or drags.
The U-joints feel solid with no abnormal wiggle.
The yoke going into the differential pushes in and out maybe 1/4 to 3/8 of an inch but doesn't wiggle side to side (I guess clockwise/counterclockwise might be a better description).
But here is my status so far....I have removed the trailing arm on the driver side rear.
The bushing halves have not separated.
The wheel bearing feels smooth backwards and forward with no spots where it catches or drags.
The U-joints feel solid with no abnormal wiggle.
The yoke going into the differential pushes in and out maybe 1/4 to 3/8 of an inch but doesn't wiggle side to side (I guess clockwise/counterclockwise might be a better description).
Tech Contributor
Joined: Aug 1999
Posts: 15,175
Likes: 3,987
From: Connecticut, USA
The yoke going into the differential pushes in and out maybe 1/4 to 3/8 of an inch but doesn't wiggle side to side (I guess clockwise/counterclockwise might be a better description).[/QUOTE]
If you have that much endplay the yokes are junk. The late 70's are known for soft yokes and that can lead to the yoke hitting the housing and grinding it down. You should get it in the air and check it for sure.
78-79 are also known for ring gear bolts backing out and shearing off or locking up the diff.
If you have that much endplay the yokes are junk. The late 70's are known for soft yokes and that can lead to the yoke hitting the housing and grinding it down. You should get it in the air and check it for sure.
78-79 are also known for ring gear bolts backing out and shearing off or locking up the diff.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Thread Starter
Instructor
Joined: Mar 2006
Posts: 198
Likes: 0
From: Kentucky
Okay, now what?
GRT1999, Thank you for the response. I've got it in the air (at least on jack stands) and the yoke does have the play that I spoke of. So what you're saying is the yokes are bad. How does one go about replacing the yokes? How much is this going to cost me? Thanks, Paul
Tech Contributor
Joined: Aug 1999
Posts: 15,175
Likes: 3,987
From: Connecticut, USA
Darrow yours did hit the posi case. I still have to put that in the lathe and see if I can face it but expect it is done.
PDA64- To replace the yokes you need to drop the diff out. Now the question comes what else does it need? When I do this I usually go through them as this point since the ground up metal has been in the oil for a while. Others have just replaced the yokes and put it back in the car. Just replacing the yokes with a stock posi setup probably will not get you in the .005-.010 range I set them to. You may still find you have .020-.030" endplay. You can drop it out and look it over and see how it is.
What will it cost? If you do the labor about $230 for basic parts if a shop does it figure about $800 for labor and marked up parts.
PDA64- To replace the yokes you need to drop the diff out. Now the question comes what else does it need? When I do this I usually go through them as this point since the ground up metal has been in the oil for a while. Others have just replaced the yokes and put it back in the car. Just replacing the yokes with a stock posi setup probably will not get you in the .005-.010 range I set them to. You may still find you have .020-.030" endplay. You can drop it out and look it over and see how it is.
What will it cost? If you do the labor about $230 for basic parts if a shop does it figure about $800 for labor and marked up parts.
Thread Starter
Instructor
Joined: Mar 2006
Posts: 198
Likes: 0
From: Kentucky
Options....
Gary,
I need to get the car back over to the painters to have a spot on the hood fixed. It's about a 15 miles trip one-way. I know that this is probably a silly question, but I'm really just looking for an opinion. Would I be damaging this thing by driving it that far or is the damage done already. I really can't get it rebuilt this week as the bucks ain't in the budget. But I have a "spare" rear end in my 63 (in the middle of a long restoration so it's not running), would I be wise to try swapping differentials before trying to drive it back to the painter? Thanks, Paul.
I need to get the car back over to the painters to have a spot on the hood fixed. It's about a 15 miles trip one-way. I know that this is probably a silly question, but I'm really just looking for an opinion. Would I be damaging this thing by driving it that far or is the damage done already. I really can't get it rebuilt this week as the bucks ain't in the budget. But I have a "spare" rear end in my 63 (in the middle of a long restoration so it's not running), would I be wise to try swapping differentials before trying to drive it back to the painter? Thanks, Paul.
Tech Contributor
Joined: Aug 1999
Posts: 15,175
Likes: 3,987
From: Connecticut, USA
Hard to say, if it's a sound from the posi clutches hammering then you'll be ok to drive it. If the u-joints or bearings are bad then they could fail in use. If you're sure they look ok then I would drive it the 15 miles.
The 63 diff will fit but look at the pinion yoke, the 78 has a larger yoke. You can get a conversions joint or swap the yokes. If you swap the yokes - look up my post on changing the pinion seal and follow it.
The 63 diff will fit but look at the pinion yoke, the 78 has a larger yoke. You can get a conversions joint or swap the yokes. If you swap the yokes - look up my post on changing the pinion seal and follow it.
Tech Contributor
Joined: Aug 1999
Posts: 15,175
Likes: 3,987
From: Connecticut, USA