Rear end question
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Joined: Dec 2017
Posts: 90
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From: Monroe NC
Rear end question
I have a 73 350 auto. When I first start it and put it in gear everything is fine as I drive it and it warms up there is a clunk in the back. It sounds metallic you can even feel as if the car is bumping. What do I need to start looking for.
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,809
From: Cool Northern Michigan
With the rear tires up on ramps, in Park, climb under there and grab the driveshaft. Should be zero play in it. If it moves, is it the U-joints or the differential?
When was the last rear axle flush? You will need two bottles of GM axle lube + one bottle of Posi modifier. ( Summit or Amazon)
When was the last rear axle flush? You will need two bottles of GM axle lube + one bottle of Posi modifier. ( Summit or Amazon)
Thread Starter
Advanced
Joined: Dec 2017
Posts: 90
Likes: 5
From: Monroe NC
With the rear tires up on ramps, in Park, climb under there and grab the driveshaft. Should be zero play in it. If it moves, is it the U-joints or the differential?
When was the last rear axle flush? You will need two bottles of GM axle lube + one bottle of Posi modifier. ( Summit or Amazon)
When was the last rear axle flush? You will need two bottles of GM axle lube + one bottle of Posi modifier. ( Summit or Amazon)
Tech Contributor
Joined: Aug 1999
Posts: 15,136
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From: Connecticut, USA
Could very well be posi chatter. When the diff gets hot, after driving about 20-30 minutes, you get to a stop and turn L or R do you feel or hear the noise then? Very common with spring loaded posi setups as used in the C2 & C3 vettes. If you hear it then you will have to vacuum out the old oil, unless someone tapped a drain, and refill it. I use 2 bottles of the current GM additive and either GM or Lucas gear oil. I like the 85-140 and change it out at 8-10k miles.
