A/T - A40 Series O/D Won't Cancel Fourth Gear
TECHNICAL BULLETIN # 197TRANSMISSION: A40 Series Overdrives
SUBJECT: Won't cancel Fourth
DATE: DEC 93
APPLICATION: Toyota/Volvo/Isuzu/Mitsubishi/Chrysler
A40 Series Overdrives (except A43DE)
WON'T CANCEL FOURTH GEAR
If the transmission stays fourth gear even when you try to cancel fourth with the O/D cancel switch, you need to find out if you have an electrical problem or a transmission problem. First disconnect the wire going to the solenoid on the outside of the transmission and road test (Figure 1). If you have no fourth gear, check for one of the electrical problems listed below. If after disconnecting the solenoid you still get fourth gear, check for one of the transmission problems listed on the next page.
POSSIBLE ELECTRICAL PROBLEMS
1. Cancel switch won't close. Check function with an ohmmeter.
2. Short circuit between the solenoid wire and a different power source. Disconnect the solenoid wire terminal at the O/D relay, and see if you still have power at the solenoid. If so, run a new wire from the solenoid to the solenoid terminal on the relay. Cut the old wire out of the circuit.
3. O/D relay is stuck or burned closed. Disconnect the relay harness. Check for continuity between pins one and two (Figure 2). If you have continuity the relay is failed closed.
4. Pin 4 is a signal wire to the cruise control unit. Make sure Pin 4 of the harness is not shorted to ground (harness disconnected). If Pin 4 of the harness is shorted to ground, the cruise control unit or harness is faulty.
POSSIBLE TRANSMISSION PROBLEMS
Leaking or stuck open solenoid. Put a piece of thick gasket paper under the solenoid and road test the vehicle. If no 3- 4 upshift occurs, replace the solenoid.
Damaged or missing check ball between the lower valve body and the lower valve body cover separator plate. Consult your manual for correct ball locations.
Reversed gaskets on the lower valve body cover separator plate (Figure 3 & 4). Make sure that the gasket with the 'bathtub' slots (upper) is installed between the valve body and plate. The gasket with no 'bathtub' slots must be installed between the lower valve body cover and the spacer plate.