4th gear is direct-drive through the transmission, via a clutch and the torque converter.

It is possible for a torque converter to fail, more common for a clutch to fail or for the pump to fail, or for a seal (or seals) to leak enough to lower the pressure to a point where the clutch isn't adequately engaged.

My friends who own transmission shops won't even open a transmission until they look at fluid level and condition, and test pressures. Usually one of these items will tell them what's wrong.

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Gone to the dark side

- Jeff