Noisey rear end
Thread Starter
4th Gear
Joined: Nov 2012
Posts: 4
Likes: 0
Noisey rear end
The rear end in my 79 sounded like I had a little man in there with a big hammer.The noise is all the time at all speeds.I replaced the u joints and that didn't help,so now I have the rear end on my work bench and am lost at this point.Does anyone know something to look for,I thought with that much noise I would find it in pieces,but looks normal to me.By the way I plan on getting help from a shop ,but don't want to be told I need a complete rebuild if I don't.Soooo does anyone have some pointers?
Melting Slicks
Joined: Aug 2008
Posts: 2,456
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From: Somerdale NJ
St. Jude Donor '11-'12-'13-'14-'15-'16-‘17-‘18
It could be something as simple as the rear differential fluid being bad. I had a similar issue with the '76 and drained the fluid and replaced with posi-rear fluid w/additive and the noise went away. When I bought it, they told me that it needed a rear, haven't had any problems since and it's been over a year.
I had the same problem in 1987 with my '86 Trans Am and replaced the fluid after my mechanic told me to use gear oil with whale oil or an additive. Drove it in a complete circle and few times and the noise went away.
The fluid breaks down over time - I'm sure with the '76, by the looks of the fluid it was original. With the Trans Am, it was supposedly due to the fact they did not put posi-rear oil in the car when it was built. (Who knows?)
Hopefully, that's the issue and not something more serious. Although, it could be ..
Good Luck!
I had the same problem in 1987 with my '86 Trans Am and replaced the fluid after my mechanic told me to use gear oil with whale oil or an additive. Drove it in a complete circle and few times and the noise went away.
The fluid breaks down over time - I'm sure with the '76, by the looks of the fluid it was original. With the Trans Am, it was supposedly due to the fact they did not put posi-rear oil in the car when it was built. (Who knows?)
Hopefully, that's the issue and not something more serious. Although, it could be ..
Good Luck!
Race Director
Joined: May 2003
Posts: 11,814
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From: Science Bitch! Mississauga, Ontario
Canadian Events Coordinator
The rear end in my 79 sounded like I had a little man in there with a big hammer.The noise is all the time at all speeds.I replaced the u joints and that didn't help,so now I have the rear end on my work bench and am lost at this point.Does anyone know something to look for,I thought with that much noise I would find it in pieces,but looks normal to me.By the way I plan on getting help from a shop ,but don't want to be told I need a complete rebuild if I don't.Soooo does anyone have some pointers?
Thread Starter
4th Gear
Joined: Nov 2012
Posts: 4
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Noisy Rear End
I looked as good as I could yesterday when I took it out,but couldn't find any broken teeth.Can the clutches make a noise like that,or is that only on turns?There doesn't seem to be a lot of free play anywhere.Nice and snug.
CF Community Team
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From: Cape Cod, Mass.
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I have heard clutches so noisy you would swear there was a mess inside the pumpkin. New 80/90 gear oil, one 4 oz bottle of GM posi lube and a few figures 8's and the noise is gone. If nothing is jumping out at you there that may well be all it needed.
Burning Brakes
Joined: Sep 2005
Posts: 1,050
Likes: 205
From: Lewes Delaware
I had some rear end noise, especially during right turns, in my 73. I did exactly what capevettes describes and the noise disappeared.
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Burning Brakes
Joined: Apr 2009
Posts: 807
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From: VIRGINIA BEACH VIRGINIA
While you have it open, change on the "C" clips on the side yokes. All you need is a pair of side snap ring pliers and the "C" clips. takes about 15 minutes and will prevent you from having to do it again at some other point.
Burning Brakes
Joined: Aug 2008
Posts: 878
Likes: 55
From: Deep South Denmark
Flatulence humor always comes to mind when questions of "noisy rear ends" appear 
Could one of the experts giving advice here please explain how bad additive could cause the rear end to make a grinding noise "all the time, at all speeds", which also means when driving in a straight line?
I'm no expert, but I thought the additive was there to stop the clutches from binding which would mean that the additive would only stop the noise when cornering?
I'm curious, that's all.
Could one of the experts giving advice here please explain how bad additive could cause the rear end to make a grinding noise "all the time, at all speeds", which also means when driving in a straight line?
I'm no expert, but I thought the additive was there to stop the clutches from binding which would mean that the additive would only stop the noise when cornering?
I'm curious, that's all.
Last edited by Danish Shark; Dec 12, 2012 at 06:17 AM.
Burning Brakes
Joined: Mar 2012
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From: Belle River Ontario
2015 C3 of Year Finalist
Myself , i wasn't insinuating that the additive was the reason for the noise itself , i was merely reminding that once you change the diff fluid and you're already under there , don't forget the additive.
Trying to save the guy from having to go back and add it later.
Trying to save the guy from having to go back and add it later.
Melting Slicks
Joined: Aug 2012
Posts: 3,487
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From: Titusville Florida
Ok, I have a question: If the fluid you get already has additive do our Vettes require that you put in anything else? Sorry, that's probably a stupid question but thought I'd ask because I don't understand why someone wouldn't but fluid that doesn't have additive in it already.
Burning Brakes
Joined: Apr 2007
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From: Pinecrest FL
2015 C3 of the Year Finalist
With the rear on the car...you cant actually get all of the gunk out with a single fluid change. I ended up doing mine twice. Drove it for about a week in between so the new fluid would pick up some of the gunk. It actually came out in clumps. Make sure to do the figure 8's at a low speed with the wheels fully locked. If you dont have room for full 8's you can do complete circles going in both directions.
Gary
Gary