69 Corvette - under carriage thumping noise
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Joined: Jan 2014
Posts: 54
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From: San Diego CA
69 Corvette - under carriage thumping noise
Hi Everyone,
I have a four-speed manual transmission C3 Vette that's been making a thumping noise.
The noise is not a one-time "clunk or thump" but when it happens, it's a bunch of them strung together (i.e. thump, thump, thump, thump). It's almost like the sound of something being stressed or creaking but loud. The sound is not uniform in duration...can be faster or slow.
It seems to only make this noise only when the car is in first gear (thumping starts when it get the car moving from a dead stop) or when I have the gear in reverse.
Once the car is in 2nd or any other gear, there's no thumping at all. I've done a search on the forum for a similar issue and just not sure if I have a problem with the differential or if this sounds like a problem with the transmission.
I greatly appreciate any suggestions, assistance or words of wisdom you can offer. Thanks in advance for your help.
Fred
I have a four-speed manual transmission C3 Vette that's been making a thumping noise.
The noise is not a one-time "clunk or thump" but when it happens, it's a bunch of them strung together (i.e. thump, thump, thump, thump). It's almost like the sound of something being stressed or creaking but loud. The sound is not uniform in duration...can be faster or slow.
It seems to only make this noise only when the car is in first gear (thumping starts when it get the car moving from a dead stop) or when I have the gear in reverse.
Once the car is in 2nd or any other gear, there's no thumping at all. I've done a search on the forum for a similar issue and just not sure if I have a problem with the differential or if this sounds like a problem with the transmission.
I greatly appreciate any suggestions, assistance or words of wisdom you can offer. Thanks in advance for your help.
Fred
Burning Brakes
Joined: Sep 2010
Posts: 822
Likes: 82
From: Columbus OH
Sure you don't have a rabbit stuck underneath that is kicking your floor pan?
Ok, I have no idea what it is at this point, but let me ask a question if I may. When you hear the sound, do you feel it anywhere? Butt of your seat? In the shifter? Gas pedal? Brake pedal? Steering wheel?
With it only being in first gear and maybe reverse, I would think something in the transmission,.
Wait, let me ask a second question. Does it do this when going in a straight line in first and reverse, or are you making a turn or a sharp turn?
Hope you find an answer.
Ok, I have no idea what it is at this point, but let me ask a question if I may. When you hear the sound, do you feel it anywhere? Butt of your seat? In the shifter? Gas pedal? Brake pedal? Steering wheel?
With it only being in first gear and maybe reverse, I would think something in the transmission,.
Wait, let me ask a second question. Does it do this when going in a straight line in first and reverse, or are you making a turn or a sharp turn?
Hope you find an answer.
Burning Brakes
Joined: Apr 2013
Posts: 1,194
Likes: 109
From: Las Vegas NV
Good questions. I had a similar sound that required a diff rebuild. The yokes were worn out to the point where they were falling into the rear end further than they should and they were hitting the diff housing.
A related symptom was a noticable negative camber on the rear wheels, even when the control arms were pulled all the way in.
A related symptom was a noticable negative camber on the rear wheels, even when the control arms were pulled all the way in.
Thread Starter
Advanced
Joined: Jan 2014
Posts: 54
Likes: 0
From: San Diego CA
Sure you don't have a rabbit stuck underneath that is kicking your floor pan?
Ok, I have no idea what it is at this point, but let me ask a question if I may. When you hear the sound, do you feel it anywhere? Butt of your seat? In the shifter? Gas pedal? Brake pedal? Steering wheel?
With it only being in first gear and maybe reverse, I would think something in the transmission,.
Wait, let me ask a second question. Does it do this when going in a straight line in first and reverse, or are you making a turn or a sharp turn?
Hope you find an answer.
Ok, I have no idea what it is at this point, but let me ask a question if I may. When you hear the sound, do you feel it anywhere? Butt of your seat? In the shifter? Gas pedal? Brake pedal? Steering wheel?
With it only being in first gear and maybe reverse, I would think something in the transmission,.
Wait, let me ask a second question. Does it do this when going in a straight line in first and reverse, or are you making a turn or a sharp turn?
Hope you find an answer.
Thread Starter
Advanced
Joined: Jan 2014
Posts: 54
Likes: 0
From: San Diego CA
Good questions. I had a similar sound that required a diff rebuild. The yokes were worn out to the point where they were falling into the rear end further than they should and they were hitting the diff housing.
A related symptom was a noticable negative camber on the rear wheels, even when the control arms were pulled all the way in.
A related symptom was a noticable negative camber on the rear wheels, even when the control arms were pulled all the way in.
Safety Car
Joined: Apr 2006
Posts: 4,057
Likes: 421
From: BC
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Joined: Jan 2014
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From: San Diego CA
Thread Starter
Advanced
Joined: Jan 2014
Posts: 54
Likes: 0
From: San Diego CA