I just checked with Richmond Gears if it would be OK to use Mobil 1 syn 75-90W
oil my Super T-10. I am relaying this for what it is worth from their tech department. Do not use any 90W
oil, natural or
synthetic that has limited slip additive in it or says will reduce chatter. Richmond says that it can actually make the
oil to slick for the synchros to work correctly.
The Mobil 1 does have the additive so I had to get some thing else. They did not push their trans oils and actually recommended a number of others like Redline NS.
I thought this might be of some interest to someone.
bkozlow