Flow of Diagnosis
PRELIMINARY DIAGNOSISTwo basic procedures are involved in making the preliminary diagnosis. One procedure is for vehicles that are driveable and an alternate procedure is for vehicles that will not back up or move forward.
Vehicle Is Driveable
1. Check the fluid level and condition.
2. Adjust the throttle and gearshift linkage before road testing if the complaint was based on delayed, erratic or harsh shifts.
3. Perform a stall test if the complaint was based on sluggish, low-speed acceleration or abnormal throttle opening requirements to maintain highway speeds with the engine in good tune.
4. Road test the vehicle and analyze the results. Perform hydraulic pressure tests.
5. Perform an air pressure test to check the clutch and band operation.
Vehicle Will Not Back Up or Move Forward
1. Check the fluid level and condition.
2. Check for broken or disconnected throttle linkage.
3. Check for broken cooler lines and loose or missing pressure port plugs.
4. Raise the vehicle, start the engine and shift the transmission into gear.
- if the propeller shafts turn but the wheels do not, the problem is in the differential or axle shafts.
- if the propeller shafts do not turn and the transmission is noisy, stop the engine, remove the oil pan and check for debris; if no debris is found, remove the transmission and check for a broken drive plate or broken drive plate-to-converter bolts, a broken converter hub, a broken input or output shaft or a broken oil pump.
- if the propeller shafts do not turn and the transmission is not noisy, perform a hydraulic pressure test to determine if the problem is that a hydraulic or mechanical component is malfunctioning.