GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2004 🢒 TopKick C-Series (Conventional) C4/C5 🢒 Transmission/Transaxle 🢒 Manual Transmission - Medium Duty 🢒 Transmission Does Not Shift into One Gear

Diagnostic Aids

If the transmission shifts into gear and then jumps out of gear, refer to Transmission Jumps Out of Gear . If it is an intermittent condition, other driveline components may be faulty.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. This test is to confirm that the clutch is not slipping. During certain conditions, the clutch may slip and feel as though the transmission is not in gear.

    2.

  2. A static shift test is performed by shifting into all gears with the engine not operating. While performing the test, you should note how the shift lever movement is felt. Also feel for the shift rails moving freely, the detent plungers operating when coming out of a gear and going in the next gear, and the synchronizer sleeve or the sliding clutch gear movement.

  3. A dynamic shift test is performed by shifting into all gears with the engine operating. Test for the correct mesh of the synchronizers sleeve or the sliding clutch gear with the speed gear selector teeth. Move the shift lever and feel for the synchronizer sleeve or the sliding clutch gear to just release from the gear, then let up on the clutch pedal. Depress the clutch pedal and move the shift lever to again engage that gear, to ensure full travel of the shift components.

Step

Action

Yes

No

DEFINITION: The shift lever will not move into a particular gear position, or the shift lever is in a gear position, and power is not delivered through the transmission.

If the transmission is equipped with an air shift control, refer to the transmission manufacturer repair manual for the correct diagnosis and repair.

1

Did you review the manual transmission symptom and perform the necessary inspections?

Go to Step 2

Go to Symptoms - Manual Transmission

2

Inspect the clutch system for slipping. Refer to Clutch Slipping in Clutch.

Is the clutch working properly?

Go to Step 3

Go to Clutch Assembly Replacement in Clutch

3

  1. Perform a static shift test on the transmission.
  2. Test for the following:
    3. • Blockage, preventing full shift lever movement
    • Excessive movement in the shift lever
    • Excessive movement in the shift control housing
    • Detent plungers or shift rails binding
    • Synchronizer sleeve moving on the hub and pressure pieces
    • Sliding clutch gear engaging

Were you able to shift into the gear position with the concern?

Go to Step 5

Go to Step 4

4

  1. Remove the shift lever. Refer to Control Lever and/or Boot Replacement .
  2. Inspect the shift lever and the shift control housing for excessive movement or wear. Refer to the transmission manufacturer repair manual.

Did you find and repair the condition.

Go to Step 8

Go to Step 6

5

  1. Perform a dynamic shift test on the transmission.
  2. Test for the following:
    3. • Detent plungers or shift rails binding
    • Synchronizer sleeve binding
    • Synchronizer sleeve engaging on the speed gear selector teeth
    • Sliding clutch gear binding
    • Sliding clutch gear engaging on the speed gear selector teeth

Were you able to shift into the gear position with the concern?

Go to Step 7

Go to Step 6

6
  1. Remove the shift cover housing. Refer to the transmission manufacturer repair manual.
  2. Inspect the shift cover components for wear or damage. Refer to the transmission manufacturer repair manual.
    3. • The shift forks
    • The internal shift control lever
    • Shift rails binding
    • Loose or missing shift fork set screws
    • Detent springs and poppets binding
    • Shift rail and lever bushings worn

Did you find and repair the condition?

Go to Step 8

Go to Step 7

7
  1. Remove the transmission. Refer to Transmission Replacement .
  2. Disassemble the transmission. Refer to the transmission manufacturer repair manual.
  3. Inspect the following transmission internal components for wear or damage:
    4. • The synchronizer sleeve selector teeth
    • The sliding clutch gear teeth
    • The speed gear selector teeth
    • The speed gear axial clearance for being excessive
    • The speed gear to mainshaft bearings and journals
    • The countershaft for being broken
    • The mainshaft for being broken
    • The countershaft gear for being stripped
    • The mainshaft gear for being stripped

Did you find and repair the condition?

Go to Step 8

Go to Diagnostic Aids

8

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 1