GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2002 🢒 GMC C Sierra - 2WD 🢒 Engine 🢒 Engine Electrical 🢒 Transmission Shifts Hard

Diagnostic Aids

An intermittent hard shift may be caused by an intermittent clutch condition. With a self adjusting clutch, the clutch may be between adjustments and not give full clutch release. This might be felt by a low clutch pedal. After several applications, the clutch may adjust properly, to give the proper pedal feel.

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 one 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. Test for the correct mesh of the synchronizers and for the clutch releasing correctly. When shifting into and out of a gear, feel for the shift detent plungers and for the synchronizers sleeve for moving freely.

    3.

  3. The transmission uses a synthetic transmission fluid that allows proper synchronizer operation. The incorrect fluid may cause hard shifting by varnish build up, or not enough lubrication for proper synchronizer operation.

Step

Action

Yes

No

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

1

Did you review the Symptoms - Manual Transmission, and perform the necessary inspections?

Go to Step 2

Go to Symptoms - Manual Transmission

2

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

Did you find or repair the condition?

Go to Step 11

Go to Step 3

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
    • Binding in the shift lever
    • Detent plungers or shift rails binding

Are you able to shift into all gears?

Go to Step 5

Go to Step 4

4

Remove the shift tower and inspect for worn or faulty components. Refer to Shift Lever Assembly Replacement .

Did you find and repair the condition?

Go to Step 11

Go to Step 5

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
    • Gear clash into only one gear
    • Gear clash into all gears

Did the transmission shift hard into all gears?

Go to Step 6

Go to Step 10

6

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

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

Go to Step 8

Go to Step 7

7

Drain and refill the transmission with the correct type fluid. Refer to Transmission Fluid Replacement .

Did you find and repair the condition?

Go to Step 11

Go to Step 8

8

  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 9

Go to Step 10

9

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

Did you find and repair the condition?

Go to Step 11

Go to Step 10

10
  1. Disassemble the transmission. Refer to Transmission Disassemble in the Transmission Unit Repair Manual.
  2. Inspect the following components for being faulty, in the gear that is hard to shift or clashing:
    3. • 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
    • Shift rail and the internal shift control lever components for wear or damage
  3. Replace worn or damaged components as necessary.

Did you find and repair the condition?

Go to Step 10

Go to Diagnostic Aids

11

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 1