Chevy Nova Forum banner

1 - 7 of 7 Posts

·
Registered
Joined
·
19 Posts
Discussion Starter #1
Hopefully someone can give me a hand on what this may be. I have a 1974 Nova Hatchback with a 3:73 posi rear. When I put the car in drive and reverse everything is fine. Once I drive the car for about 10 minutes or so and begin to slow to speeds of 15 mph and below I get a loud "clunking" sound and jerking coming from the rear. Driving at speeds greater than 15 I am fine. I replaced both the front and rear u joints, inspected the brakes, put the posi additive and lube in rear. Any advice would greatly be appediated


Sent from my iPad using AG Free
 

·
Premium Member
Joined
·
4,125 Posts
Sounds like you don't have the right rear gear oil, or the right amount of friction modifier in it. You're more than likely hearing the clutches popping and grabbing after it gets warm.

If you're running the stock Eaton posi unit, you can not run synthetic oil, period. I had a long telephone conversation with the owner/chemist at Redline. He convinced me that I could. 1 year later, I had to rebuild my posi. Don't risk it. Use the factory GM oil and the GM modifier.

Get ahold of Miles (jbimmolate) and confirm.

Chuck
 

·
Moderator
Joined
·
4,535 Posts
ok First are both rear tire the same size, brand & tread life? Next did you use synthetic gear oil or standard? Third what type of additive did you use?

Miles
 

·
Registered
Joined
·
19 Posts
Discussion Starter #5
First off thanks for the quick responses..I put 75w90 gear oil..synthetic blend..Transx posi additive..tires are both the same size and have same tread life


Sent from my iPad using AG Free
 

·
Moderator
Joined
·
4,535 Posts
Synthetics do not mix well with additives and most posi manufacturers say to not use synthetic fluids since it shortens the life span of the posi unit. I would go with a good 80-90wt oil and use either ford or GM additve.

Miles
 

·
Registered
Joined
·
19 Posts
Discussion Starter #7
Sounds like a fluid change will be in the works. Thanks for the input Miles and others!!


Sent from my iPad using AG Free
 
1 - 7 of 7 Posts
Top