What gear lube would be best to add a quart to a 1996 355 manual trans?
Don't know what was in there before? When you start mixing fluids, you don't know what the result will be. I use Redline 75W90NS* with a couple of capfuls of Redline friction modifier. *Not "shockproof". This was deemed by Redline to be unsuitable for the F355.