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1969 Nova sm block,350 turbo Ohio
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Discussion Starter · #1 ·
I have a 1969 Nova-came with 6 cyl and Powerglide.On the 154 mile trip home,I noticed a feeling of shifting or slippage on low speed movement,forward or reverse.I thought it was the transmission as I have felt this type of low speed slippage in PGs before.
I switched out the 6 and pg for a small v-8 and 350 Turbo.I rebuilt the motor and bought the transmission from a rebuilder.After getting the car going again and putting a few miles on the new drivetrain parts,motor and transmission run great,I noticed that I still had the shifting feeling in the rear.After carefully testing slow movement of the car,I could tell I had
a thumping in the rear axle-I could actually see the drivers side wheel "thump"out at very slow speed especially in reverse.I checked the u joints and they are good.
I had a similar thing happen years ago in a Camaro and it turned out to be a broken thrust washer under one of the pinion (spider)gears.Replaced the washer and it was fixed.I expected to find the same thing or possibly the carrier case worn out where the pinion shaft goes thru.I pulled the cover and was surprised to find an Eaton style posi-traction unit!!This is on a 6 cyl 2.73 axle car!
I carefully looked at all the parts and could find nothing wrong(to my limited
knowledge).The case looked good and the thrust washers were oK.The pin was tight.
I have no experience with the Eaton style posi.I slowly turned the tires by hand looking for problems.The only thing that looked odd to me was the spider gears would move slightly along the pinion shaft-this could be normal.I rolled out the gears and clutch packs and found out that the Eaton units have "keepers"on the sides of the clutch packs.I couldn't see any way to reinstall the packs sideways in the housing so I pulled out the carrier.
I inspected the parts and saw nothing wrong(again,to my limited knowledge).Using a method from a 1970 Chevy Overhaul Manual,I tried to use a dial indicator to check pinion gear clearance.It seemed to be too much that is about .012 and the manual says .001 to .006.So I shimmed both sides to bring the clearance to about .003.Reassembled the rear with new fluid and posi-trac additive.
At first I thought it was better,but after driving for a few miles I found I still had the problem.So I realize that it may be something else.Sorry about the long story but I wanted to give all the facts as I know them.
So---I have a low speed thumping or knocking in my 2.73 posi trac rear axle,especially when it is plenty warmed up.--Any help????
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