Q: 4l60e transmission shifting problem

The 1-2 shift failure on the 4L60E is often due to a faulty throttle position sensor (TPS). Test the sensor (there should be a smooth, linear electrical response over the range of motion) or substitute a known good unit. A more serious cause of 1-2 shift failure on the 4L60E is a leak in the 2nd gear apply circuit (servo assembly or 1-2 accumulator). You can test for this by using an external pressure gauge. If you see a big drop in pressure when the PCM commands 2nd gear, there is a leak. It is also possible to have inadequate line pressure due to a leaking boost valve, clogged EPC filter screen, failing EPC solenoid, or possibly leaky seals throughout the transmission. The problem with the overdrive and no 4th gear is probably mechanical in nature but would require further diagnosis. Often, no 4th gear is accompanied by noise (due to hard parts failure) and/or 1st or 3rd won’t work either. The transmission you have is very common, parts are very readily available, and is easily rebuildable so you needn’t worry. If you can’t repair it on the car, just rebuild it. If you want a conclusive diagnostic performed by a certified Mechanic, dispatched by YourMechanic right to your location, please request a transmission shift diagnostic and the responding certified mechanic will get this resolved for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.