BUMP noise when taking off
Thread Starter
Le Mans Master
Joined: Feb 2000
Posts: 9,600
Likes: 88
From: Springfield PA
Philly 'Burbs Events Coordinator
BUMP noise when taking off
When I engage the clutch to take off in forward or reverse I hear a bump noise. It's one bump, sounds like it's coming from the rear, doesn't happen or I don't hear it while running through the gears. Doesn't always happen, if I engage the clutch easy no bump.
I've checked everything I can think of underneath. Any ideas?
I've checked everything I can think of underneath. Any ideas?
Instructor
Joined: Aug 2001
Posts: 201
Likes: 0
From: Daytona Beach
A clunk can come from where the beam (trans. to rear diff) mounts to the differential.
Someone makes a kit to reinforce it which solves the clunking but I can't put my finger on who sells it at the moment.
Vettedave
Someone makes a kit to reinforce it which solves the clunking but I can't put my finger on who sells it at the moment.
Vettedave
Instructor
Joined: May 1999
Posts: 206
Likes: 0
From: Lebanon Ohio
Id INSPECT the U-joints in the halfshafts carefully.. I had the same deal with mine... I put it on the lift...spun it around/saw nothing... Eventually it got worse and worse So I lifted it again and found a bad bearing in the u-joint at the wheel...Installed new joints..car was/is perfect since..
Thread Starter
Le Mans Master
Joined: Feb 2000
Posts: 9,600
Likes: 88
From: Springfield PA
Philly 'Burbs Events Coordinator
Andy: I did the busing about 20 months ago, have checked and all seems tight.
Vettedave: Beam plates, installed them when I did the bushings.
Kenwood and Togo: I've replaced the half sharft U joints about 30K ago and the drive shaft about 15K ago. Visually the ujoints all look good. I'd hate to think I only got 30K out of them.
At this point I guess I'll put her back up on the lift and tighten EVERYTHING and see what that does. Maybe I'll find something that doesn't look loose but is
Vettedave: Beam plates, installed them when I did the bushings.
Kenwood and Togo: I've replaced the half sharft U joints about 30K ago and the drive shaft about 15K ago. Visually the ujoints all look good. I'd hate to think I only got 30K out of them.
At this point I guess I'll put her back up on the lift and tighten EVERYTHING and see what that does. Maybe I'll find something that doesn't look loose but is
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
Racer
Joined: Apr 2005
Posts: 484
Likes: 5
From: Madison Wisconsin
I had a very similar noise on my 93 ZF-6. I read on one of the links that some anti-seize on the spline where it mates with the wheel hubs solves the problem. I pulled my driver's side half shaft, applied anti-seize to the spline and changed the two u-joints. The noise is now gone. It's hard to say which solved the problem. Something to consider.
Racer
Joined: Nov 2002
Posts: 270
Likes: 0
From: North of KC MO
Originally Posted by Mtrhd329
Had that problem in my camaro and it turned out to be a worn out transmission mount. Might want to check that out they are relatively cheap to replace. Just my .02 
Good Luck
Thread Starter
Le Mans Master
Joined: Feb 2000
Posts: 9,600
Likes: 88
From: Springfield PA
Philly 'Burbs Events Coordinator
There isn't a transmission mount on a C4, only a connection to the C beam. I checked everything again today, everything seems to be tight. The only "play" in the drivetrain seems to be at the rear. Could it be the rear?
Waka, Waka, Waka!
Joined: Jun 2002
Posts: 2,435
Likes: 2
From: Richmond Virginia
CI 4-6-8 & 10 Veteran
St. Jude Contributor
I had the same problem. I learned that there is a bronze bushing on the driveshaft yoke where it slipps into the tranny. (I didn't know about this one when I changed what I THOUGHT were all of the bushings) It wears out and lets the shaft clunk when first putting it into gear, but makes no further noise. Unless you put it into reverse, when it thunks (just once) again.
If you let it go and get worse, you will feel the wobble at high speeds. the speed you notice it at will gradually get lower as the bushing wears more.
And, if you are totally stupid, it will get bad enough to rip the rear seal and start leaking tranny fluid until one day you will take a hard turn and uncover the tranny pump fuild pick-up. :o
I know you said that everythign seemed tight, but if the wheels were on the ground when you checked, the rear (connection to the Diff) of the shaft would have kept it from turning. Unless you were using a sizable cheater, you were probably not generating anywhere near the torque required to notice the play in the joint.
Recheck the slip-yoke bushing on the drive shaft, or you might join me in the " I bought a transmission because I was stupid" club.
If you let it go and get worse, you will feel the wobble at high speeds. the speed you notice it at will gradually get lower as the bushing wears more.
And, if you are totally stupid, it will get bad enough to rip the rear seal and start leaking tranny fluid until one day you will take a hard turn and uncover the tranny pump fuild pick-up. :o
I know you said that everythign seemed tight, but if the wheels were on the ground when you checked, the rear (connection to the Diff) of the shaft would have kept it from turning. Unless you were using a sizable cheater, you were probably not generating anywhere near the torque required to notice the play in the joint.
Recheck the slip-yoke bushing on the drive shaft, or you might join me in the " I bought a transmission because I was stupid" club.
Last edited by Fozzy_Bear; Oct 25, 2005 at 11:23 AM.
Thread Starter
Le Mans Master
Joined: Feb 2000
Posts: 9,600
Likes: 88
From: Springfield PA
Philly 'Burbs Events Coordinator
I have an M6, don't know how different the bushings are vs auto.
Checked with it up in the air, I believe I saw enough movement to say the u joints look good. I'll have to check the d/s yoke.
Checked with it up in the air, I believe I saw enough movement to say the u joints look good. I'll have to check the d/s yoke.
Intermediate
Joined: Mar 2005
Posts: 41
Likes: 0
95 slip yoke bushing?
Originally Posted by Fozzy_Bear
I had the same problem. I learned that there is a bronze bushing on the driveshaft yoke where it slipps into the tranny. (I didn't know about this one when I changed what I THOUGHT were all of the bushings) It wears out and lets the shaft clunk when first putting it into gear, but makes no further noise. Unless you put it into reverse, when it thunks (just once) again.
If you let it go and get worse, you will feel the wobble at high speeds. the speed you notice it at will gradually get lower as the bushing wears more.
And, if you are totally stupid, it will get bad enough to rip the rear seal and start leaking tranny fluid until one day you will take a hard turn and uncover the tranny pump fuild pick-up. :o
I know you said that everythign seemed tight, but if the wheels were on the ground when you checked, the rear (connection to the Diff) of the shaft would have kept it from turning. Unless you were using a sizable cheater, you were probably not generating anywhere near the torque required to notice the play in the joint.
Recheck the slip-yoke bushing on the drive shaft, or you might join me in the " I bought a transmission because I was stupid" club.
If you let it go and get worse, you will feel the wobble at high speeds. the speed you notice it at will gradually get lower as the bushing wears more.
And, if you are totally stupid, it will get bad enough to rip the rear seal and start leaking tranny fluid until one day you will take a hard turn and uncover the tranny pump fuild pick-up. :o
I know you said that everythign seemed tight, but if the wheels were on the ground when you checked, the rear (connection to the Diff) of the shaft would have kept it from turning. Unless you were using a sizable cheater, you were probably not generating anywhere near the torque required to notice the play in the joint.
Recheck the slip-yoke bushing on the drive shaft, or you might join me in the " I bought a transmission because I was stupid" club.
Safety Car
Joined: Apr 2004
Posts: 4,532
Likes: 7
From: Lahaina Hi
Originally Posted by Mtrhd329
Had that problem in my camaro and it turned out to be a worn out transmission mount. Might want to check that out they are relatively cheap to replace. Just my .02
Did you check the leaf spring for cracks on the left and right side of the center mount?
When you hear the clunk going foward stop the car and look at the top of the tire and see if it has a line on it from the wheel well.
I would also lift the car and use a rubber mallet and bang on the tires inside edge and outside edge and see if you can duplicate the noise.
Other wise I would say replace the rear end dampner drive shaft mounts.
Waka, Waka, Waka!
Joined: Jun 2002
Posts: 2,435
Likes: 2
From: Richmond Virginia
CI 4-6-8 & 10 Veteran
St. Jude Contributor
Originally Posted by larrynash
I've had this problem on my 1995 for 90 k miles. A few dealers had the car a dozen times trying to fix it under warrenty. I don't see a bushing in my GM manual. I was going to change the diff next. Does a 95 have this bushing? Is it replaceable on the slip yoke?
I suppose that they could have been feeding me a line, but I have used them many times and they have proven trustworthy.