Tranny experts - ATF in 39 trans ??

[Mike51Merc]

Originally Posted by TStiles

You may also want to investigate top-quality synthetic transmission oils of the proper viscosity (GL4 spec in a 140 wt). This stuff is incredibly slippery, so if any lubricant is going to help resolve your problem, synthetic is your best bet.

Actually, the opposite is true. Synchronizers act like brakes. If you give them more slippery lube, they'll be worse not better.

[36coupe]

Originally Posted by rockfla

Use a can of STP in it, it will be the smoothest shifting transmission you;ll own.

I changed the oil to 80-140 in my 38 and it was miserable to shift. I added a 1/2 can of STP and I haven't thought about the transmission since.
I think it helps everything to stop spinning so the next gear can be engaged.