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Rear clunking again

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Old Sep 25, 2006 | 07:55 PM
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Default Rear clunking again

The jury is still out on the slow speed clunking of the rear end when warmed up. However, yesterday I noticed that the R Rear wheel has a camber problem and is leaning in on the top (not plumb). I jacked up the car and was able to move the wheels at least 4 inches pushing the top of the tire and pulling the bottom. The play seemed to be the half shafts at the rear end. Is this normal? Worn bearings?
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Old Sep 25, 2006 | 09:29 PM
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It sounds like your stub axles are shot. There seems to be a rash of these lately. i have a few pics in another thread called "differential pics" showing the damage caused by worn out stub axles.
Mike
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Old Sep 25, 2006 | 11:36 PM
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I saw your pics....and that is scary. I guess it's time to pull those half shafts out and have a look.
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Old Sep 25, 2006 | 11:39 PM
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Actually I meant to also mention that I'm trying not to get too discouraged about this car, but honestly....right now...I feel like it's a pile of crap.
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Old Sep 25, 2006 | 11:46 PM
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Don't get discouraged. At some point in time all vettes go thru this. The good news is that with the high quality of the new parts this is a one time replacement.
Mike
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Old Sep 26, 2006 | 12:12 AM
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This is a condition that seldom occured on the old ones, but starting in 75 and increasing in frequency through 79 it became epidemic. I had long discussions with the General back then, but they never would admit that there was a problem, eventhough it was readily apparent. The conditon results in a lot of metal ground up and deposited in the gears etc. This results in accelerated wear and positration clutch chatter. That is what you hear when you take off from a start after the rear is warm.
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Old Sep 26, 2006 | 06:57 AM
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Wombvette,
The reason I was told for the rapid wear was reduction in the rockwell hardness rating. Had the same problem starting in 78 with cam wear and valve guide wear. I remember hearing a statement from a GM rep saying the reason for the wear is people are driving slower and the cams aren't getting enough lube because of it. Still laughing at that one.
Mike
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Old Sep 26, 2006 | 09:15 AM
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Yep, those were the dark days of the domestic auto industry. The corporate bean counters and shoddy workmanship cheapen the product and the corporation makes more money. But, that type thinking resulted in the move to imports. After that, even if you produce a good product, the public will not know or buy it. Its is telling on them now, eventhough there are some good products our there now.
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Old Sep 26, 2006 | 11:21 AM
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corvette maniac,
Don't get discouraged. The pics tracdogg has posted are of my diff. I started out with Trailing arm and suspension rebuild and found the trouble with the stubs. Tracdogg has my Diff and has built the new trailing arms for me. All is good.
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Old Sep 26, 2006 | 11:27 AM
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Hi Chris,
I'll be posting more pics today of your parts. I've got a call in for a gas tank but no reply yet. I'll try again a little later.

Maniac,
When you see how everything comes out you'll feel a lot better. I'll try to post more pics to show you what to look for. Where are you located?

Mike
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Old Sep 26, 2006 | 12:13 PM
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Originally Posted by tracdogg2
Hi Chris,
I'll be posting more pics today of your parts. I've got a call in for a gas tank but no reply yet. I'll try again a little later.

Maniac,
When you see how everything comes out you'll feel a lot better. I'll try to post more pics to show you what to look for. Where are you located?

Mike
Cool...thanks for the encouragement guys. The good thing is that I do it all myself...it's just that I have another project (`79 Firebird 4 speed/ 400). I do feel encouraged to know what the problem is. The next step, I suppose is to pull those half shafts and see what those splines look like. I will take pics as I go along.

I am in Woodstock, GA.
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Old Sep 26, 2006 | 12:19 PM
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You'll need to pull the whole rear end to check it out and/ or make repairs. First pull the halfshafts and see if the yokes come out with them.
Mike
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Old Sep 26, 2006 | 12:56 PM
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Good luck with your replacements,

I too started with a Trailing Arm replacement and found the differential was junk, Bubba had rebuilt.

The new 500 HP stroker just hastened the differential demise.

Don't get too discouraged.
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Old Sep 26, 2006 | 01:07 PM
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Originally Posted by wombvette
This is a condition that seldom occured on the old ones, but starting in 75 and increasing in frequency through 79 it became epidemic. I had long discussions with the General back then, but they never would admit that there was a problem, eventhough it was readily apparent. The conditon results in a lot of metal ground up and deposited in the gears etc. This results in accelerated wear and positration clutch chatter. That is what you hear when you take off from a start after the rear is warm.
I can only assume that is partially due to the whale oil additive being banned in '75. Whale oil was universally accepted as the only posi-unit additive at the time. Posi-unit problems skyrocketed once the ban took affect, since no synthetic replacement had been developed. I had a friend at a Porsche dealership who said they stockpiled cases of the stuff to keep 911 transaxles quiet.
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Old Sep 26, 2006 | 05:03 PM
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There are 2 issues here - yoke wear from case hardening - or lack of it and posi setup procedures with the springs and clutches.
If the yokes are worn you'll have more then .040" endplay in them. Case hardening is about .030 deep. The clutches used and the setup cause the hammering which the whale oil was thoguht to be a fix, it wasn't so they went to the snowflake clutches and this just made the clutches break in use.





The only way to eliminate the problems are to use hardened tip yokes and tune the posi. Both time consuming and expensive if you have to farm them out.

Gary
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Old Sep 26, 2006 | 06:21 PM
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Originally Posted by gtr1999
There are 2 issues here - yoke wear from case hardening - or lack of it and posi setup procedures with the springs and clutches.
If the yokes are worn you'll have more then .040" endplay in them. Case hardening is about .030 deep. The clutches used and the setup cause the hammering which the whale oil was thoguht to be a fix, it wasn't so they went to the snowflake clutches and this just made the clutches break in use.





The only way to eliminate the problems are to use hardened tip yokes and tune the posi. Both time consuming and expensive if you have to farm them out.

Gary

That broken clutch disk is exactly what happened in mine.
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