2000 blazer 4.3 auto drives 55 miles to work when its cold torque converter locks up fine after warm- bout 20 miles a small hill then instead of 65 mph and 2000 rpm i get 65mph and 2900rpm. cleaned iac and mass and had mecanic check with obd tester and found lockup solinoid being commanded to lock up but no lock up replaced solinoid with new same problem

 

Probably a worn valve body?? I'm not sure if there's a sonnax repair sleeve for 4l60e like there is for 4l80e, but I bet there is if you look around or talk to a reputable tranny shop. It takes a special reamer to bore out a hole in your valve body and then a steel insert is pressed in for the TCC valve to ride in. Typically <$200 parts&labor if you bring the valve body in for them to do it on the bench (dropping the valve body yourself isn't a cake job, but it isn't too bad if you have a flat place to work underneath).

Hope that helps...

 

thanks it just gave me a code (haven't read it yet) ie check engine lite... like the idea of the valve body... new solinoid does the same thing