My C6 is slipping on shifts when cold. Say on the cold mornings now usually around 30*-40* I start and let it idle anywhere from 1-3 minutes then drive off.It will slip on shifts, particularly the 2-3 shift, and worse when coming to a stop then accelerating again like for a stop sign. Feels like it's sort of between gears. If I shift it manually until I've driven a couple miles it does not slip at all. So clearly it's being lazy changing gears until things are warm. Truck is an '86 with allegedly 90k miles or so but has a reman trans and also a large cooler in front of the rad in addition to the in rad cooler.
What might this be? Old hard seals leaking until they warm up and get pliable enough to seal pressure? Vacuum/modulator/regulator on pump issues? Vacuum is pretty rock solid at 24" give or take an inch. Fluid is right about the full mark when idling hot, maybe a little dark and slightly bad smelling but it's not real dark and nasty cooked smelling, seems more like old and a bit overdue for a change.
Anything I can check or try free or cheap to resolve this or is it just a sign it's due for a rebuild? Plan is for a ZF5 swap but I'm not having much luck finding a decent used ZF5 within a few hundred miles. May end up having to bite the bullet and order a rebuilt unit since the few that do pop up people want at least half what a rebuilder jobbie cost but for a 200k+ mile piece that's cracked and welded all over. Would be nice to have the luxury of choosing when to do the swap rather than the C6 crap out in the dead of winter and need to do it then.
What might this be? Old hard seals leaking until they warm up and get pliable enough to seal pressure? Vacuum/modulator/regulator on pump issues? Vacuum is pretty rock solid at 24" give or take an inch. Fluid is right about the full mark when idling hot, maybe a little dark and slightly bad smelling but it's not real dark and nasty cooked smelling, seems more like old and a bit overdue for a change.
Anything I can check or try free or cheap to resolve this or is it just a sign it's due for a rebuild? Plan is for a ZF5 swap but I'm not having much luck finding a decent used ZF5 within a few hundred miles. May end up having to bite the bullet and order a rebuilt unit since the few that do pop up people want at least half what a rebuilder jobbie cost but for a 200k+ mile piece that's cracked and welded all over. Would be nice to have the luxury of choosing when to do the swap rather than the C6 crap out in the dead of winter and need to do it then.