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 Shifts Hard

Diagnostic Aids

An intermittent hard shift may be caused by an intermittent clutch condition.

Test Description

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

  1. A static shift test is performed by shifting into all of the gear positions with the engine not operating. While performing the test, you should note how the shift lever movement is felt. Also while shifting from one gear to the other, feel for binding in the shift rails. You should be able to feel the detent plungers operating when coming out of a gear and going into a gear.

  2. A dynamic shift test is performed by shifting into the gear positions with the engine operating. If synchronized transmission, test for the correct mesh of the synchronizers. When shifting into a gear and out of the gear, feel the shift detent plungers and for the synchronizers sleeve or for the sliding clutch moving freely. The test also determines if the clutch system is operating properly.

Step

Action

Yes

No

DEFINITION: The transmission does not shift smoothly or without difficulty from one gear to the other.

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 operations and perform the necessary inspections?

Go to Step 2

Go to Symptoms - Manual Transmission

2

Inspect the clutch system for proper operation. Refer to Clutch System Description and Operation in Clutch.

Did you find and repair the condition?

Go to Step 12

Go to Step 3

3

  1. Perform a static shift test on the transmission.
  2. Test for the following conditions:
    3. • Blockage preventing full shift lever movement
    • Excessive movement in the shift lever
    • Binding in the shift lever
    • Detent plungers or shift rails binding

Did the transmission shift hard into all gears?

Go to Step 9

Go to Step 4

4

  1. Perform a dynamic shift test on the transmission.
  2. Test for the following conditions:
    3. • Detent plungers or shift rails binding
    • Synchronizer sleeve binding, if equipped
    • Sliding clutch binding, if equipped
    • Gear clash into only one gear
    • Gear clash into all gears

Did the transmission shift hard into all gears?

Go to Step 9

Go to Step 5

5

Inspect the transmission for the correct fluid level and type of the transmission fluid. Refer to Transmission Fluid Check .

Is the transmission at the correct level and proper fluid being used?

Go to Step 7

Go to Step 6

6

Drain the transmission and fill with the correct type fluid. Refer to Transmission Oil Changing .

Did you find and repair the condition?

Go to Step 12

Go to Step 7

7
  1. Remove the shift lever. Refer to Control Lever and/or Boot Replacement .
  2. Inspect the shift lever for worn or damaged components. Refer to the transmission manufactures service manual.

Did you find and repair the condition?

Go to Step 12

Go to Step 8

8

Remove the shift control housing and inspect for worn or faulty components. Refer to the transmission manufacturer service manual.

Did you find and repair the condition?

Go to step 12

Go to Step 11

9

  1. Remove the transmission. Refer to Transmission Replacement .
  2. Inspect the clutch pressure plate and/or clutch driven plate.

Is the clutch pressure plate and/or clutch driven plate worn or faulty?

Go to Step 10

Go to Step 11

10

Replace the clutch assembly. Refer to Clutch Assembly Replacement in Clutch.

Did you find and repair the condition?

Go to Step 12

Go to Step 11

11
  1. Remove the transmission. Refer to Transmission Replacement .
  2. Disassemble the transmission. Refer to the transmission manufacturer service manual.
  3. Inspect the transmission for faulty components in the gear that is hard to shift or clashing.
    4. • Excessive synchronizers blocking ring to gear clearance
    • Synchronizer hub external splines worn or damaged
    • Excessive axial clearance in the speed gear
    • Mainshaft to speed gear bearing or journal worn
    • Sliding clutch worn or damaged, non synchronized
    • Twisted or damaged mainshaft key, non synchronized

Did you find and repair the condition?

Go to Step 12

Go to Diagnostic Aids

12

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 1