Don't know if this should go in the lubricants and oils section or here, but I figure you guys know more about these old trucks that the explorer and harley davidson truck guys.

I've got a 1963 3-speed manual, no overdrive. I believe it to be a T86. The manual calls for SAE 90 straight mineral oil (or SAE 80 straight mineral oil under 10F), or SAE 50 (or 30) motor oil.

Is it ok to use mobil 1 synthetic gear lube (75W-90) in the transmission? Some other synthetic? Recommendations?


Bob

 

Yes it is okay, but it might be a waste of money. I switched to a synthetic (Royal Purple 50wt) in the NP435 in the hope that it would shift a bit better but I noticed no improvement over the gear oil.
Eric

 

Thanks. Was just reading the shop manual and it was explicit about no additives. Wondered what that was all about, especially since it said motor oil was ok (which has additives).

Bob

 

Good question that I wish I could answer as well. I share your concerns -- wonder a lot if "motor oil" in 1963 is the same as "motor oil" in 2003. A lot of new additives in there, all very fine for engines, but for a tranny????

I ended up with straight 50w motor oil in my t-18. But who knows if its right. My Dad informs me he was running 90w tranny gear oil in it for years -- never bothered to read the book, just pumped in gear grease!!!!