A/T - No Overdrive Or Shifts 1st, 2nd to Overdrive
TECHNICAL BULLETIN # 319DATE: 1996
TRANSMISSION: G4A-HL
SUBJECT: No OD or shifts 1st, 2nd, OD
APPLICATION: 323 Mazda
G4A-HL
No Overdrive or Shifts 1st, 2nd, Overdrive
The first step in diagnosis is to determine if the transaxle is skipping third gear or not shifting to overdrive.
Step 1
Drive the vehicle with the tires oft the ground at 3,000 engine rpm. If the transaxle is in third gear the speedometer will read approximately 52-58 mph. If so there is a no overdrive condition; go to step two. If the transaxle is in overdrive the speedometer will read approximately 72-76 mph; go to step five.
Step 2
Disconnect the case connector to the overdrive cancel solenoid and drive the vehicle, If the transaxle shifts to overdrive go to step three, if not go to step four.
Step 3
With the ignition on, the overdrive cancel solenoid is supplied battery voltage. The water temperature switch, kickdown switch, overdrive cancel switch and cruise control module supply ground the solenoid to cancel overdrive (figure one).
Disconnect the case connector and probe the positive and negative wires with a voltmeter. If one of the switches or the cruise control module are grounding the circuit the voltmeter will read 12v (with the ignition on). Disconnect the switches (including the module) one at a time. When the item at fault is disconnected the voltmeter will read zero volts.
Note
The water temperature switch should ground the circuit when the coolant temperature is below 160°F (70°C). With a temperature probe verify coolant temperature is above 160°F (70°C) before assuming the switch is defective.
WARNING
Do not disconnect the cruise control module with The ignition on.
Step 4
Check governor and T.V. pressure (figure two) and compare the readings to the pressure chart (figure three).
If governor pressure is low remove the governor and inspect for wear in the bore or on the shaft. Remove the side pan, blow air into the governor pressure tap while blocking the feed hole inside of the governor bore. Listen for leaks in the valve body and repair as necessary.
If TV. pressure is high at idle and cannot be adjusted, the throttle valve may be sticking or the TV. balance hole may need to be enlarged (figure four).
If governor and TV. pressures are okay, the problem may be solenoid related. The solenoid must be closed to allow overdrive. Therefore, a leaking solenoid or solenoid circuit can cause a no overdrive condition. Blow air into the solenoid and solenoid bore of the valve body to find possible leaks.
If no leaks are found, the problem may be a stuck 3-4 shift valve or too much travel of the 3-4 shift rear-valve (figure five).
Install the 3-4 shift valve assembly without the spring. With all valves pushed toward the stopper plug, the 3-4 shift rear-valve should stop before coming out of the bore of wall number three (figure six).
If the 3-4 shift rear-valve travels too far it can cock in the bore, preventing the 3-4 shift valve from upshifting. To adjust the travel of the rear-valve make a shim out of shim stock or other round metal to The dimensions needed (figure seven).
Install the complete assembly with the shim inside of the spring pocket of the 3-4 shift valve.
Step 5
A symptom of skipping third gear can be caused by the 3-4 shift valve stuck in the upshifted position.
This may be caused by a worn 3-4 shift sleeve or 3-4 shift plug traveling partially out of the support land, allowing the shift plug to cock, and holding the 3-4 shift valve in the upshifted position (figure 8).
Because the support land is offset .050" toward the stopper plug, installing the 3-4 shift sleeve backward (ID marks facing the stopper plug) may help if the shift plug is traveling partially out of the support land.