Shifts out of overdrive when not accelerating?

[bvanetten]

Hey all, I'm new here and had a question about my 98 3500 Silverado. I just bought this truck not long ago and when test driving it never did this but now that I have driven it more it will do it on and off. When I accelerate I have no problems but when I go to just keep a constant speed or put the cruise control on it shifts out of overdrive like I was pressing on the gas to accelerate but I'm not. It usually happens immediately as I let off the gas. It's really bad around 55-70. The craziest part is that it only does every other time or so that I drive it. Any ideas? Thanks in advance!

[gmtech4]

It is a fully electronic transmission , if it bounces outa gear ( not lock up TC )then you have a clutch retention problem , or the end is near i think