[Bigdav160]

All shifts including Fourth gear are hydraulic. Sometimes the weighted head comes loose on the governor and the valve will not have enough travel. It will not shift past 3rd. Not too hard to remove and check.

Lockup is different and electrically controlled through the TCC solenoid. Yes, on fuel injected models the 4th gear pressure switch tells the ECM when the trans has shifted to 4th and the ECM then grounds D to lock up the clutch.

My experience is the TCC solenoid has very little to no noise when energized.