Originally Posted by cheezehead69
Ok i have a 1997 4l60e with a fresh rebuild that me and a friend did. New clutches, plates, band, tourqe converter, shift kit and so on. it works great in all gears, shifts nice but in 3 and 4th it bump shifts. so anywhere from 60 to 120 kmh it will do this. But only at slight acceleration or if you let off and let the tranny freewheel and then apply a light amount of gas. if you get into it it down shifts and works like normal. I have changed the fluid since the rebuild as well as check all the selinoids. Does any one have any advice. Thank you Jayson.
Are you getting any codes with this?
There's lots of reasons, but off hand given that line pressure does follow the depth your foot is in the throttle, I'd suspect a leaky valve such as the 3-4 Relay/4-3 Sequencer. A leakage induced pressure loss here would let 4th drop to 3 rd on a light cruise throttle. Stepping on the pedal would bring line pressure up and snap the valve back into the 4th gear position. However, wear, being wear, eventually you won't get 4th at all. This is a pretty nervous valve so it wears on its bore pretty hard which lets oil out. There's fixes for it.
Keep in mind these are complicated beasts and I'm shooting in the dark. But I bet something in that valve body circuit isn't as good as it needs to be and this is one of several common problems with that circuit.
Keep in mind that the master control is these computer controlled solenoid valves, but they just replace the old governor versus throttle control valves. The rest of the old stuff that sequences and times the shifts is still in there. Along with a bunch of what always becomes leaky check valves