Im going to be hauling a large loaded horse trailer over long distances fairly often this next year and I was wondering if I could drain a quart of the Amsoil gear oil already in my NV5600 and add a quart of Redline Mt90 in its place. I thought I recall reading that this could provided slightly better shifting and/or protection for the NV5600 6spd when towing over longer distances. When my transmission is nice and warm (been driving steadily for more than an hour at highway speeds), it seems as though the amsoil becomes just a little thin for my liking-exspecially when Im towing in the summer with elevated tranny temps and shifting at higher RPM's ( the shifting feels like I could use just a little extra friction to help slow things down). Im essentially asking whether or not 1 quart of the "heavier" Redline MT-90 will safely "get along" with 3.5 qts of the "thinner" Amsoil gear oil.
--Let me know what yall have to say. THANKS, Drew