Odd transmission problem

[Xppcxthekid]

99 2wd Tahoe
Trans shifts just fine in normal driving conditions and no hard shifts at all. But for a while now whenever I'm driving on the freeway i let off the gas to coast and it will feel like it downshifts but it only drops maybe 3-400 Rpms. And when I press the gas it shifts back up. I think maybe overdrive? But I spent a few hours looking it up and can find anything on this situation. Help appreciated. No CEL, no leaks. And it does the same thing in cruise controls

 

[SunlitComet]

just sound like the overdrive and/or converter lockup doing it thing.

---------- Post added at 11:57 PM ---------- Previous post was at 11:56 PM ----------

also note that there are also a lot of codes that dont turn on a light. you have to search for them with a scanner.

 

[Xppcxthekid]

K

I have a scanner none come up

 

[SunlitComet]

it seriously sounds just like normal od and converter lockup. when you are on a steady pedal on say flat land you are in od and lockup doing say 70 at 1900 rpm. when you let up on the pedal or hit the brakes the tc unlocks and because your foot is off the gas the rpm will drop a few hundred but only so much since you are still in over drive at the moment. if you press the gas to maintain the speed again but not aggressively and you are near the speed you were aiming for the rpm will go back up above the 1900 mark obviously but only so much cause you are likely still in the od gear then suddenly when tc lock up occurs the go back down a few hundred to 1900 again.

the automatic control of the tranny is dependent on a few different sensors and the shift pattern table programmed into the pcm. if you are absolutely sure something is wrong yo can ask for an opinion of a tranny shop. but so far as you describe the events it sounds like it is doing its thing.

 

[Xppcxthekid]

Okay appreciate the info guys. I'll just leave it be than. I thought it was weird because none of my other cars do it

 

[Texas_Racer]

I would bet money it is as suggested the converter lockup