Q: Transmission shifts up and down randomly.

This may be a result of a faulty transmission control module. A faulty transmission control module may cause a delay in acceleration or erratic shifting of gears. The transmission control module has various sensors such as vehicle speed sensors, wheel speed sensors, throttle position sensors, turbine speed sensor, and transmission fluid temperature sensors that all direct information to it in order for it to perform it’s function. A kick down switch is also operated by the TCM which controls when the transmission downshifts. When this is faulty, this may cause the erratic downshifting out of overdrive you describe. Any of these may also affect the way the transmission control module performs and controls the transmission and the shifting of your vehicle. I would suggest having a professional from Your Mechanic come to your location to properly diagnose your transmission shifting problem.