69 Differential Help
Guys,
I have just had some fairly exstensivel restoration work done on my 69 350 coupe at the rear suspension. All of the components were removed, overhauled and restored to NCRS stanards of appearance, etc. The shop primarily does muscle cars, but has done several C-2 and C-3 Corvettes in the past few years. Everything was rebuilt or new: Trailing arms by Bairs, rebuilt spring, rebuilt half shafts - the works. The finished product looks fantastic, however.....
On the test drive I noticed a whine in the differential primarily at highway speeds when the trottle is released in an unloaded condition. Also, I noticed a bumping sound at very low speed (less than 10mph) coming from the rear end of the car as well. (Naturally prior to this restoration work I had no noise or problems at all from the rear suspension other than cosmetc condition).
This car uses a 3.08 Positrac unit which was sent out for rebuild using new bearings and a new clutch pak by this shop. The unit made no noise prior to the rebuild and in fact the rebuilder said the unit looked great inside.
We jacked the car up in such a way to move the wheels, etc. We immediately noticed that the wheel could be rotated inboard and outboard almost an inch! The trailing arm wheel brgs do not appear to be the culprit. It seems tight and correct and when moving the wheel back and forth the whole trailing arm tries to move, not just the brg assy. When you face the wheel and grasp it at the top and bottom it will move in and out almost an inch back and forth and the differential side yokes move in and out almost 3/16" as you do this. I have done some work on standard rear ends but not Corvettes or independant suspension units. The way I understand the repair manual drawings, the side yokes should not be moving in and out and in fact are captured internally and should be shimmed to a specified clearance.
So this is my question - should the side yokes on a 69 3.08 positrac rear end move in and out. I have a friend with a 66 and he is pretty sure his wheels will not rotate inboard and outboard like mine is doing. Can someone please shed some light on this? My inclination is that the differential needs to come out but I would really like some insight before I next talk to the shop.
As always, thanks for your help in advance!!!
Brad Hood
I have just had some fairly exstensivel restoration work done on my 69 350 coupe at the rear suspension. All of the components were removed, overhauled and restored to NCRS stanards of appearance, etc. The shop primarily does muscle cars, but has done several C-2 and C-3 Corvettes in the past few years. Everything was rebuilt or new: Trailing arms by Bairs, rebuilt spring, rebuilt half shafts - the works. The finished product looks fantastic, however.....
On the test drive I noticed a whine in the differential primarily at highway speeds when the trottle is released in an unloaded condition. Also, I noticed a bumping sound at very low speed (less than 10mph) coming from the rear end of the car as well. (Naturally prior to this restoration work I had no noise or problems at all from the rear suspension other than cosmetc condition).
This car uses a 3.08 Positrac unit which was sent out for rebuild using new bearings and a new clutch pak by this shop. The unit made no noise prior to the rebuild and in fact the rebuilder said the unit looked great inside.
We jacked the car up in such a way to move the wheels, etc. We immediately noticed that the wheel could be rotated inboard and outboard almost an inch! The trailing arm wheel brgs do not appear to be the culprit. It seems tight and correct and when moving the wheel back and forth the whole trailing arm tries to move, not just the brg assy. When you face the wheel and grasp it at the top and bottom it will move in and out almost an inch back and forth and the differential side yokes move in and out almost 3/16" as you do this. I have done some work on standard rear ends but not Corvettes or independant suspension units. The way I understand the repair manual drawings, the side yokes should not be moving in and out and in fact are captured internally and should be shimmed to a specified clearance.
So this is my question - should the side yokes on a 69 3.08 positrac rear end move in and out. I have a friend with a 66 and he is pretty sure his wheels will not rotate inboard and outboard like mine is doing. Can someone please shed some light on this? My inclination is that the differential needs to come out but I would really like some insight before I next talk to the shop.
As always, thanks for your help in advance!!!
Brad Hood
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