[redmodelt]

"will harm the babbit in your rear." It there is still babbitt thrust washers in it (not babbitt, type of white metal), more then likely the rear end will be going south anyway no matter what lube is used!
Look for a G4 140 lube at the parts store. While the other rear end lubes sold will wear away the brass thrust washers, the amount most of us drive our Ts, would take our lifetime and maybe several others for it to become an issue.