Inspection and Verification

A troubleshooting guide has been put together to assist in diagnosing transmission-related problems. Use the transmission noise evaluation procedure and troubleshooting guides on the following pages, or refer to Section 08-00. Remember, it is important to get an accurate description of the complaint before any diagnosis can be performed. Ask questions as to whether it occurs hot or cold, during shifting, driving at a particular speed or in a particular gear. If possible, have the customer demonstrate the concern.

Cold Transmission

• Drive the vehicle in all gears (1-5 and reverse gears).
• Evaluate the noise in neutral. Check if there are any noise changes in a particular gear, i.e., 4th gear. In 4th gear, the countershaft cluster gear (7113) is not under load.
• Check if the noise increases when the transmission (7003) is warming up.
• See if the noise is related to engine speed, road speed or gear selection.

Warm Transmission

• Check all gears plus reverse gear and make note of any noise changes in a particular gear.
• Check noise in neutral while parked. Check if the noise disappears at a certain engine rpm or with the clutch pedal depressed.
• Drive in the gear in which the noise is most noticeable. Press in the clutch pedal and leave the gear engaged. If the noise changes or disappears, the noise may be amplified by the vibration of the engine (6007).
• Drive under the same condition again. Press the clutch pedal in and shift into neutral. Release the clutch pedal while the vehicle is coasting down the road. Evaluate the noise, as the rear axle assembly (4006) turns the mainshaft.

Additional Testing For 4x4 Trucks (Non-Electronic Shift)

• Check for any noise change when shifting the transfer case (7A195) between 4x2, 4 high, 4 low or into neutral.
• With the vehicle at a complete stop and the transfer case in neutral, shift through all the gears and evaluate noise at different engine rpm. Check for any noises in neutral at different engine rpm.

NOTE: To isolate clutch concerns from transmission concerns, operate the transmission at no-load. On 4x4 models, place the transfer case in neutral. Remove the driveshaft on 4x2 models. Run the engine at 3000 rpm and operate the transmission throughout ranges with the clutch engaged. If hard shifting concern (power to transmission) disappears, the concern may be in the clutch system. An improperly operating clutch can result in hard shifting that is most noticeable in 1st, 2nd, and reverse. The hydraulic release mechanism must work properly. Continued operation with a defective clutch system may result in premature wear or damage of synchronizer (7124).

Hard shifting or difficulty engaging gears may be the result of improper clutch function. Check the release system travel. Minimum travel for the concentric slave cylinder bearing (4.9L and 5.8L engines) and the external system slave cylinder push rod (7.3L and 7.5L engines) is 11mm (7/16 inch). If system travel is less than 11mm, this is an indication of problems in the release system such as excessive flexing of the instrument panel (04320), cracked instrument panel reinforcement at the clutch master cylinder mounting and air or water in the hydraulic clutch hose. Refer to Section 08-00.

If the release system travel is greater than 11mm, and the clutch is suspected, check for clutch reserve as follows:

1. Set the parking brake control (2780) and put the transmission in neutral.

2. With the clutch pedal fully depressed, shift into reverse, then shift half-way between reverse and neutral to defeat the synchronizer.

3. Allow the clutch pedal to fully return and adjust the position of shift control selector lever and housing to obtain light contact between the gear teeth. A slight grind will occur.

4. Slowly depress the clutch pedal until grinding stops. Measure the clutch pedal travel from this position to the full down position (clutch reserve position).

This clutch reserve dimension should be at least 1-1/2 inches. If the reserve is less than 1-1/2 inches, and there are no hydraulic control system concerns, remove the transmission and check for excessive clutch wear. On the 7.3L diesel and 7.5L engines, check for contamination of clutch release hub and bearing and binding on the bearing retainer. Replace the clutch assembly or clutch release hub and bearing as required.

NOTE: On the 4.9L and 5.8L vehicles, the case (7005) is ribbed in order to reduce gear rattle and gear rollover noises.