Idk where to start this. The mm I Just got has a 1-2 shift issue. Sometimes it'll slip or lag when shifting. It did it when I got the truck and the owner is a big mighty max guy. He gave me 5 qts royal purple ATF, gasket/filter kit along with some engine gaskets. The fluid is dark but not brown or black and he doesnt think it's been changed in awhile.

I'm curious if anyone has used royal purple ATF for these transmissions without flushing all the old stuff out since the RP is synthetic. Plus RP is for SP2/3 trannies and the MM tranny calls for SP.