1970 GTO; What is best Posi Rear gear lube?
I have a 1970 GTO and I just changed the oil in my rear axle 3:55 posi limit diff. The problem is now the rear slips pretty badly in each gear. I used Mobil 1 75 -90W synthetic gear oil and GM posi additive, which were recommended by parts store. My mistake. The rear ran fine before I changed the oil so I'm going to change the oil again and hope that fixes the problem.
After reading other posts, my question is which rear oil should I use? And does it slip because I used synthetic or because I used 90 and not 140?
The most common answer I've read is to use either Torco rgo 75w 140 or Torco rgo 85w 140.
Any thoughts would be appreciated.
Last edited by TheBestVMan; 02-29-2012 at 03:06 PM.
Reason: shorter tiltle