I have a 56 Chevy with 454 and a TH400 tranny. I had someone put in 4:10 gears and now I have to re-torque them. NAPA and others have no idea what lubricant I need to put in the pumpkin. It is a posi-trac (because someone told me that because it left two tire marks on squeling tires.)
Can anyone help?? THX...

if it is a posi trac rear end then you will need to add the special posi trac additive with the gear oil. not doing so could burn up the clutches on the posi unit.

NAPA should be able to tell you what gear oil you should fill it with....so maybe try a different NAPA since the guys at your local one don't seem to be able to look it up.

You may aslo want to call your local dealership and see what they suggest.

chevy dealer parts counter has the limited slip additive its about 8 bucks a bottle

80w90 is what oil to use


you better run the stamping code on the axle tube with the chevy dealer parts counter to make sure its really lim slip

just because it left black marks with both tires doesnt mean much


good luck

Why would you need to re-torque them If you do pull out each bolt, clean it as well as the threads in the ring gear with brake cleaner, apply red loctite, and then torque it.

It has been my experience to use fully synthetic oil in the rear end. It cost more, but the gears will last a lot longer. The regular gear oil will foam a lot and will not work as good. I found this out by racing on the dirt track.

If you're running a 56 10 bolt, just clean up the third member and look for a giant letter "P" cast into it. If you don't have that then you don't have posi. You have to have that housing to run the posi. From what I understand they came in 'Vettes, so you'd be lucky to have scored one. Its worth about 550$ on ebay.

Someone correct me if I'm wrong! Dont want to put forth bad info, but this is correct to the best of my knowlege.