I have a 1993 with a 4.3L Vortec, 4-speed auto, Tahoe LT trim. The transmission has been acting funny lately. It has been accelerating fine and shifting through the gears fine, but every so often, it acts as if is shifts down to 1st or 2nd when I start decelerating from 55-60, then when I get down to 10-15 mph it hard shifts out and starts acting normal again. Anyone else ever have this problem or might know what it is? It was purchased about a month ago and the previous owner replaced the engine about 20,000 miles ago and the tranny about 500 miles ago, but it was also over a year ago. He never driven it much and decided to sell it to get rid of it.

 

Could be a misadjusted TV cable.

 

If this is a 700R4 then start by adjusting the cable... after that maybe check the filter to not have fallen down to the bottom of the pan. anyone else?