The Stovebolt Site Forums The Parking Lot '60-'66 Trucks Posi chatter

Recently purchased a '63 C10 with 12 bolt posi and 3.73. Only a few very short trips before servicing the rear end. I gave it a good cleaning with Varsol and refilled with Lucas synthetic gear oil (75-90?). I also added GM additive when I first noticed some chatter. I still have a posi chatter. Should I get rid of the Lucas? Any other suggestions? Thanks OldsCool

I'd add more GM Posi additive.

I put a 12 bolt posi out of a late 60's Impala in my Model A. The Model A is so light compared to the Impala I had to add twice the amount of GM Posi Lube to keep it from chattering.

And yes, it still hooks up both rear tires in sraight line acceleration.

Hope that helps.

John

The chatter is caused by the cone clutches grabbing as the rear end differentiates axle speed in a low-speed turn. Regardless of where you get the posi additive, Ford, Chrysler, or GM, it's all the same stuff. Mix it according to the directions on the bottle, and it should cure your problem. At heavy throttle the axles will lock if any slippage is present, so the additive is just to prevent chatter at low speeds with little if any power applied.
Jerry

Thanks John. I'll give it a try. -OldsCool

Thanks Jerry. That sounds right. Low speed turns is where the chatter occurs.

And if it doesn't cure the chattering, use more additive. In my case the amount specified on the additive bottle wasn't enough. It still chattered badly when cornering. But doubling the amount of additive cured the chattering issue.

John