1999 silverado transmission not downshifting

My 1999 Silverado does not want to downshift sometimes...especially when driven for a long period of time. Any suggestions?

Won't downshift like when passing or like going 60 then slow to 10 and it stays in hi gear?

Lance

Won't downshift like when passing or like going 60 then slow to 10 and it stays in hi gear?

Lance
It won't downshift when slowing down to a stop. When I try to take off again it is still in high gear...it is "bogged down". Sometimes I manually put it into first or second gear to get it to take off right.

Just a guess but maybe your TCC (Torque converter clutch) is staying engaged. This is controled by the PCM (powertrain control module). That's about all I know, probably not a driveway fix, time for a specialist.

Lance