I agree
Rear end clunking noise
Thread Starter
Advanced
Joined: May 2008
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From: Apex NC
Rear end clunking noise
I have a 70 454, 4 spd that makes a clunking sound, but only when starting out in 1st gear and after it has been driven for a while. Someone said it sounds like the rear end clutch has gone bad. The drive axles appear to be ok, so I don't think the noise is from them. No noise when in 2nd thru 4th. Appears to make noise when torqued in 1st and after it has warmed up. Any help will be appreciated.
Racer
Joined: Jul 2005
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If your car is pointed directly straight, it's not the clutches.
If it only happens when your car is taking off from a stop but is turning a little, the it's likely the clutches - but that doesn't necessarily mean they need replacement.
If it only happens when your car is taking off from a stop but is turning a little, the it's likely the clutches - but that doesn't necessarily mean they need replacement.
Intermediate
Joined: Jul 2009
Posts: 25
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From: Knoxville Tennessee
Someone told me that the GM posi-trac additive will take care of that chattering if it is the clutches. Might want someone elses opinion, but mine is doing the same thing and I'm getting ready to add some along with some Royal Purple.
Le Mans Master
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From: Tampa Florida
Racer
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From: Charlotte NC
Thread Starter
Advanced
Joined: May 2008
Posts: 58
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From: Apex NC
Rear End Clunking Noise
Thanks for the info all of you sent it. I have the GM Lube on order.
Can you tell me if the differential on a 70 has a drain plug or do I need to pump it out the side fill plug?
Can you tell me if the differential on a 70 has a drain plug or do I need to pump it out the side fill plug?
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Le Mans Master
Joined: Oct 2006
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From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
No drain plug. Sorry. either you split the case, suck it out thru the fill, or install a drain plug.
While you're under the car, look at the front snubber cushion, shock mounts, crossmember cushions, U-Joints, strut rods, and sway bar mounts. Any of those could also cause a clunk. Most likely the front snubber.
While you're under the car, look at the front snubber cushion, shock mounts, crossmember cushions, U-Joints, strut rods, and sway bar mounts. Any of those could also cause a clunk. Most likely the front snubber.
Race Director
Joined: May 2005
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From: Millington Illinois
St. Jude Donor '08-'09
Be careful. I had a clunk in the rear on my 72. Started to fix it. I said "while Im at it I might as well"...................
$18,000 and 3 years later I was the proud owner of a frame up restored numbers matching correct L48 automatic 1972 corvette.
$18,000 and 3 years later I was the proud owner of a frame up restored numbers matching correct L48 automatic 1972 corvette.
Le Mans Master
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From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
63mako, I understand how that can happen but to the OP just change the lube and GM additive and make a few figure 8's at low speed and see if that helps. Then you'll have $17,940 left to do other stuff. PG.
Race Director
Joined: May 2005
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From: Millington Illinois
St. Jude Donor '08-'09
Racer
Joined: Sep 2002
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From: san diego ca
Yep, scary.
Keep us posted on the progress Chad...I may be in the same boat. Mine's been making a "clunk" when starting from a stop and turning right. Been that way for years and I've always hoped it wouldn't turn into an 18K re-do. Redo of rear gear oil is prolly in order anyway.
Keep us posted on the progress Chad...I may be in the same boat. Mine's been making a "clunk" when starting from a stop and turning right. Been that way for years and I've always hoped it wouldn't turn into an 18K re-do. Redo of rear gear oil is prolly in order anyway.
