kostelacd69

iTrader: (4)

my 2001 silverado has a 6.0 and a 4l80 it randomly will start shifting hard on the 1 2 and 2 3 shifts and the converter will not lock. if you shut the truck off and drive again sometimes it works right and others it wont. looked in the tune and nothing has changed. got in all data and the only common thing those have are the same power wire that feed those three. so i went in and manualy locked the converter. it works when i tell it to. ideas?????

GMCtrk

iTrader: (27)

It sounds like your converter clutch has gone or is going out. This can cause the PCM to command maximum line pressure which would account for your hard shifts. Any SES light?

kostelacd69

iTrader: (4)

no lights on. when i tell the converter to lock it does and when i load it and build boost it holds tight, so it doesnt seem to me that the converter is junk.

GMCtrk

iTrader: (27)

Sounds like an internal trans issue then.

kostelacd69

iTrader: (4)

yeah thats what i was thinking but if i can tell it to work and it does that tells me that the pcm isnt telling what to do. right??