By itself;
Full synthetic is Too slippery
Most gearoils are too heavy
ATF is too thin.
The oil needs to have a fairly heavy body too help match the speeds between the heavy geartrain and the bad-boy clutch disc. But if it's too heavy, it's hard to squeeze it out from the between the brass rings and the shiny polished cones. The brass lasts extra long, but shifts are slow.
If the oil is too thin, the gear train wants to keep on spinning (that's physics), and the synchro has to do all the work, and the shifts are slow. Eventually it gives up.
If the oil is too slippery,shifting is frustratingly slow.
The problem is that Chrysler did not provide adequate oil channels on their cones or in their brass rings, like other manufacturers did. And those heavy, nearly indestructible gears really need them.
To solve this, I cut three channels in the faces of each cone. They are about equidistant apart and slightly V-shaped and about 1/32" deep and 1/4" wide. With this mod, I can run any oil without any clash, and shifts are much faster, and require way less effort. The brass rings sem to lasy much longer as well. Ima guessing I have 75000 or more miles on the last set of used-when-installed rings.
After some experimentation, I settled on a 50/50 mix of ATF and 75wt Gearoil.It shifts a lil faster on straight ATF, but I thought it prudent to help the cluster pin a bit, so in went the gearoil. I'ma streeter so long-life trumps milliseconds.
I have tried a synthetic for a bit, but that stuff is desperate to escape the tranny.Penzoil I think it was.
