erradic shifting,shifts realfast

Hello, This is likely going to be related to the pressure control solenoid manifold or the pressure sensor on that manifold. The 4t65e transmission has been known to have erratic shifting due to these failures, and the best way to diagnose this issue is to have the transmission scanned by a professional to observe the operation of the transmission.

Do you have a check engine lamp on?

AAMCO offers free trans diagnosis - no obligation!