My dad is visiting for a few days and left to his own devices put new rear brakes and wheel seals on my 1965 Autocar A75...also decided to change oil in the rear end and transmissions.  So now that every thing is drained... with what should we refill the 134C rear end? 

My initial guess is that 75W140 would be fine but I wanted to check with the old heads to make sure that there wasn't a different requirement on this older axle.

Best regards,

Matt