I'd like to replace my tranny fluid with GM Synchromesh, but I've found that my local parts store sells AC Delco Synchromesh manual tranny fluid and AC Delco Synchromesh manual tranny fluid with friction modifier. Neither one crossreferences the corresponding GM part number. Are there two different GM /Pennzoil Synchromesh fluids or just one? So confused...

Thanks.

EDIT: Looks like the one with the FM is designed for 3/4 ton with LSD. It has a corresponding GM part number 12377916 and is also synchromesh. I think I'm going to try the non-FM stuff. FWIW, I can't find the Pennzoil brand stuff anywhere around here.