Grinding Rear End
Thread Starter
5th Gear
Joined: Oct 2012
Posts: 5
Likes: 0
From: Elizabeth City North Carolina
Grinding Rear End
I resently purchased a 79, L-82 4 speed with approx 149K miles. The car is in overall good shape but needs serious TLC in just about every category. It is a driver but I need to settle a few issues before I am comefortable with some old parts. Namely, In my differential area. I have changed the gear oil and one CV joint on the main shaft, but I hear a "grinding" sound when starting off, or in a right or left turn. It feels solid during straight accelerations.I did not add positraction lubricant so could this be a source of the noise?
Drifting
Joined: Dec 2004
Posts: 1,714
Likes: 42
From: Austin Texas
regardless the issue you have a posi rear so add the additive.
if you put it on jack stands can you turn a wheel and make the sound? this could help you isolate the issue. If you can replicate it, then you could do things like disconnect one of the half shafts, test, then remove the other and see if it lies in the differential or within one of the trailing arms be it brakes or bearings.
if you put it on jack stands can you turn a wheel and make the sound? this could help you isolate the issue. If you can replicate it, then you could do things like disconnect one of the half shafts, test, then remove the other and see if it lies in the differential or within one of the trailing arms be it brakes or bearings.
Last edited by johnt365; Nov 5, 2012 at 07:48 PM.
Thread Starter
5th Gear
Joined: Oct 2012
Posts: 5
Likes: 0
From: Elizabeth City North Carolina
Great advice. Can i get this lubricant at most auto parts stores like Auto Zone or is it a dealer item? Or perhaps, i should just order the lube kit from Ecklers. I didn't realise there was a special lubricant until I read the owners manual. Live and learn,, It's all part of the dream! Thanks guys. So whats this special lube do?
Drifting
Joined: Jul 2002
Posts: 1,995
Likes: 110
From: Garland Texas
79 vettes have the softest stub axles. Usually by 60k they are completely worn out. At 149K the stub axles may be grinding against the housing which sounds like the noise you are hearing. You need to jack it up and look for metal shavings where the axles go into the diff. Better yet post some pics.
Mike
Mike
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,445
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
79 vettes have the softest stub axles. Usually by 60k they are completely worn out. At 149K the stub axles may be grinding against the housing which sounds like the noise you are hearing. You need to jack it up and look for metal shavings where the axles go into the diff. Better yet post some pics.
Mike
Mike
My 79 yokes were gone before i had 50,000 miles. The outer part of the yoke was grinding into the diff. housing and yokes were worn past the snap ring. It trashed the whole rearend
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Le Mans Master
Joined: Jan 2006
Posts: 6,506
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From: Butler Pa
Thread Starter
5th Gear
Joined: Oct 2012
Posts: 5
Likes: 0
From: Elizabeth City North Carolina
I used a standard 90 wt gear oil. I'm sure it didn't have the additive in it. I'll get this baby on a lift in 2 weeks and check deeper into it. I also have to replace an old Holley fuel pump that leaks. This car was rode hard then parked for several years. Definatley a long term project. But it's mine !!
Burning Brakes
Joined: Feb 2011
Posts: 849
Likes: 0
From: Woodland California
Wrong gear oil and no lube.
Terrible combo.
Ralph
Terrible combo.
Ralph
I used a standard 90 wt gear oil. I'm sure it didn't have the additive in it. I'll get this baby on a lift in 2 weeks and check deeper into it. I also have to replace an old Holley fuel pump that leaks. This car was rode hard then parked for several years. Definatley a long term project. But it's mine !!
5th Gear
Joined: Nov 2012
Posts: 5
Likes: 0
That grinding noise you have been hearing was the starter motor gear grinding and damaging the teeth on the flywheel. The flywheel is between the engine and the transmission so either the engine or the transmission has to come out of the car to gain access to the flywheel.
asset tags
asset tags
Last edited by shane23; Nov 10, 2012 at 05:07 AM.
Burning Brakes
Joined: Feb 2011
Posts: 849
Likes: 0
From: Woodland California
Really. You did see this part of his post didn't you?
" I hear a "grinding" sound when starting off, or in a right or left turn. It feels solid during straight accelerations."
R~
Changing old gear oil which is worn out, and replacing it with the wrong weight oil and no additive would do nothing to improve rear end noise.
The noise would appear when the poi-traction was not able to slip in a turn.
I used 75-90 conventional oil and GM additive.
That's what was recommended my the manufacturer of the rear end.
" I hear a "grinding" sound when starting off, or in a right or left turn. It feels solid during straight accelerations."
R~
That grinding noise you have been hearing was the starter motor gear grinding and damaging the teeth on the flywheel. The flywheel is between the engine and the transmission so either the engine or the transmission has to come out of the car to gain access to the flywheel.
The noise would appear when the poi-traction was not able to slip in a turn.
I used 75-90 conventional oil and GM additive.
That's what was recommended my the manufacturer of the rear end.
Last edited by Ralphbf; Nov 7, 2012 at 01:53 AM.
Le Mans Master
Joined: Jan 2006
Posts: 6,506
Likes: 139
From: Butler Pa
That grinding noise you have been hearing was the starter motor gear grinding and damaging the teeth on the flywheel. The flywheel is between the engine and the transmission so either the engine or the transmission has to come out of the car to gain access to the flywheel.
