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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 963 (Manual Transmission -- NV 3500) >> Diagnostic Information and Procedures >> Transmission Jumps Out of Gear >> Test Description

Test Description

WARNING: This page is about a different car, the 2004 GMC Sierra and 2004 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.

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

  1. 2:  A static shift test is performed by shifting into all gear positions with the engine not operating. While performing the test, slowly move the shift lever. Feel for proper movement of the shift lever and transmission internal shift components.
  2. 4:  A dynamic shift test is performed by shifting into all gear positions with the engine operating. Test for the correct mesh of the synchronizers sleeve and the speed gear selector teeth. Move the shift lever, and feel for the synchronizer sleeve to release form the gear, and then let up on the clutch pedal. Depress the clutch pedal and move the shift lever to re-engage the gear, to ensure full travel of the shift components.
  3. 5:  This step inspects for worn or damaged transmission or engine mounts. Loose mounts may cause a shock on the transmission allowing for gear disengagement.
  4. 6:  This step inspects for the misalignment of the clutch to transmission. Misalignment may put a bind on the input shaft, allowing for the input shaft or the mainshaft to tip.
  5. 8:  This step inspects the pilot bearing and the pilot bearing journal on the input shaft. A worn pilot bearing or input shaft may allow the input shaft to tip, causing gear disengagement.
Transmission Jumps Out of Gear

Step Action Yes No
DEFINITION: Gear disengagement occurs during acceleration or deceleration.
1 Did you review the Symptoms - Manual Transmission, and perform the necessary inspections? Go to Step 2  Go toSymptoms - Manual Transmission 
  1. Perform a static shift test.
  2. Test for the following:
    • Blockage preventing full shift lever movement
    • Excessive movement in the shift lever
    • Detent plungers engaging in the shift rails
    • Synchronizer pressure pieces on the synchronizer sleeves
Did the transmission shift completely into all gears?
Go to Step 4  Go to Step 3 
3 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 10  Go to Step 4 
  1. Perform a dynamic shift test on the transmission.
  2. Test for the following:
    • Synchronizer sleeve engagement to the speed gear selector teeth
    • Detent plungers engaging in the shift rails
Did the transmission shift completely into all gears?
Go to Step 5  Go to Step 8 
Inspect the engine and/or transmission mounts. Refer to Transmission Mount Replacement .
Did you find and repair the condition?
Go to Step 10  Go to Step 6 
Inspect the clutch housing for loose bolts or misalignment.
Are there any loose bolts or misalignment?
Go to Step 7  Go to Step 8 
7
  1. Align the housing, if required.
  2. Tighten any loose housing bolts. Refer to Transmission Replacement .
Did you find and repair the condition?
Go to Step 10  Go to Step 8 
  1. Remove the transmission. Refer to Transmission Replacement .
  2. Remove the clutch assembly. Refer to Clutch Assembly Replacement in Clutch.
  3. Inspect the pilot bearing for being faulty.
  4. Inspect the input shaft for excessive wear at the pilot bearing.
Did you find and repair the condition?
Go to Step 10  Go to Step 9 
9
  1. Disassemble the transmission. Refer to Transmission Disassemble in Transmission Unit Repair article.
  2. Inspect the following components for wear or damage:
    • The shift rails
    • The detent plungers and springs
    • The shift forks
    • The synchronizer sleeve and speed gear selector teeth
    • The mainshaft to input shaft bearing and journals
    • The speed gear bearings and journals
    • The speed gear axial clearance
    • The mainshaft center and rear bearings
Did you find and repair the condition?
Go to Step 10  Go to Diagnostic Aids
10 Operate the system in order to verify the repair.
Did you correct the condition?
System OK Go to Step 1