Rear End Clunk?
Thread Starter
Melting Slicks
Joined: Apr 2001
Posts: 2,030
Likes: 363
From: Lubbock Texas
Rear End Clunk?
My '73 is currently in the shop being dyno tuned. While there I asked the mechanic to look at the auto transmisson (TH400). It was shifting fairly hard and making a clunk noise when shifting into gear from either park or neutral.
He called and said it is not the transmission but the clunk is coming from the rear end.
There are no other symptoms. There is no noise coming from the rear during either low or high speed operation. No noise or clunks during turns. Posi-trac appears to be working fine.
A search turned up two possibilities - one is that the front differential mount is loose and/or the rubber mount is in need of replacement. The other is possible loose bolts in the rear end to cross member connection.
Are there any other possibilities?
DC
He called and said it is not the transmission but the clunk is coming from the rear end.
There are no other symptoms. There is no noise coming from the rear during either low or high speed operation. No noise or clunks during turns. Posi-trac appears to be working fine.
A search turned up two possibilities - one is that the front differential mount is loose and/or the rubber mount is in need of replacement. The other is possible loose bolts in the rear end to cross member connection.
Are there any other possibilities?
DC
Race Director
Joined: Feb 1999
Posts: 19,659
Likes: 34
From: Lenoir City Tennessee
Ci 6, 8 & 10 Veteran
St. Jude Donor '05-'06-'07-'08-'09-'10-'11-'12-'13-'14-'15
Melting Slicks
Joined: May 1999
Posts: 2,897
Likes: 0
From: Moon Township PA
Eddie 70 hit the nail on the head and even gave you photos.
your symptoms are classic for this type of failure. If you don't do your own work, this is a fairly straight forward repair for your mechanic. If you do your own work, this is very easy to do, just count on scraped knuckles and an hour lost. The procedure is in the GM Service Manual.
your symptoms are classic for this type of failure. If you don't do your own work, this is a fairly straight forward repair for your mechanic. If you do your own work, this is very easy to do, just count on scraped knuckles and an hour lost. The procedure is in the GM Service Manual.
Thread Starter
Melting Slicks
Joined: Apr 2001
Posts: 2,030
Likes: 363
From: Lubbock Texas
Eddie 70 hit the nail on the head and even gave you photos. your symptoms are classic for this type of failure. If you don't do your own work, this is a fairly straight forward repair for your mechanic. If you do your own work, this is very easy to do, just count on scraped knuckles and an hour lost. The procedure is in the GM Service Manual.
your symptoms are classic for this type of failure. If you don't do your own work, this is a fairly straight forward repair for your mechanic. If you do your own work, this is very easy to do, just count on scraped knuckles and an hour lost. The procedure is in the GM Service Manual.You've reminded me that I need to add the service manual to the list of stuff I want to order - thanks.
DC
Melting Slicks
Joined: Mar 2008
Posts: 2,336
Likes: 1
From: North Bellmore Ny
St. Jude Donor '09
This is most likely your problem
Melting Slicks
Joined: May 1999
Posts: 2,897
Likes: 0
From: Moon Township PA
Thanks guys. I do as much of my own work as possible and this should be no problem. I'll give the mechanic a heads up in the morning and ask him to do a visual inspection to confirm.
You've reminded me that I need to add the service manual to the list of stuff I want to order - thanks.
DC
You've reminded me that I need to add the service manual to the list of stuff I want to order - thanks.
DC
I really doubt that a visual inspection will show anything for the simple reason that the only thing that can be viewed is the bolt head. For the cost of the setup, guessing around $45, it is pretty easy just to swap out the old for a new one. That rubber doughnut sits up in the front of the differential mounting point and sits between the frame and the diff nose. The GM manual gives the procedure, even telling you how to keep the nose of the diff from pivoting up, iirc.
Gary
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Instructor
Joined: Sep 2006
Posts: 211
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From: Searcy Arkansas
For a DIY guy, the reprinted GM Service Manual is the ONLY way to go, imo.
I really doubt that a visual inspection will show anything for the simple reason that the only thing that can be viewed is the bolt head. For the cost of the setup, guessing around $45, it is pretty easy just to swap out the old for a new one. That rubber doughnut sits up in the front of the differential mounting point and sits between the frame and the diff nose. The GM manual gives the procedure, even telling you how to keep the nose of the diff from pivoting up, iirc.
Gary
I really doubt that a visual inspection will show anything for the simple reason that the only thing that can be viewed is the bolt head. For the cost of the setup, guessing around $45, it is pretty easy just to swap out the old for a new one. That rubber doughnut sits up in the front of the differential mounting point and sits between the frame and the diff nose. The GM manual gives the procedure, even telling you how to keep the nose of the diff from pivoting up, iirc.
Gary
Thread Starter
Melting Slicks
Joined: Apr 2001
Posts: 2,030
Likes: 363
From: Lubbock Texas
Not yet. Car is still in the shop being checked and tuned. Mechanic said the front bushing and all mounting bolts are tight and in good shape. Doesn't appear to be u-joints either. He thinks its coming from inside the diff. When I get it back I'll double check everything and then will change the fluid to see if that helps. Previous owner said the rear diff is the only part of the car that did not get any attention when he restored it so maybe it's just overdue for a fluid change.
DC
DC
