GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2001 🢒 Sonoma Pickup - 4WD 🢒 Engine 🢒 Engine Electrical 🢒 Transmission Locked in One Gear

Diagnostic Aids

If the transmission is locked, engaging the clutch will kill the engine. If the shift control components and the clutch system operations are working properly, the problem is caused by internal damage, such as a dented or damaged shift fork, and the transmission must be removed from the vehicle for repairs. You should also perform a static shift and a dynamic shift test.

Test Description

The number(s) below refer to the step number(s) on the diagnostic table.

  1. This step is checking for a faulty actuator cylinder.

    2.

  2. This step is checking for a dented or damaged shift fork.

  3. This step is checking for worn or damaged internal components.

Step

Action

Yes

No

DEFINITION: The transmission cannot be shifted out of a gear.

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 transmission fluid level. Refer to Fluid Replacement .

Is the transmission fluid level correct?

Go to Step 4

Go to Step 3

3

Add transmission fluid if necessary.

Can the transmission be shifted out of gear?

System OK

Go to Step 5

4

Inspect for the correct type transmission fluid.

Is the correct type transmission fluid being used?

Go to Step 6

Go to Step 5

5

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

Did you find and repair the condition?

System OK

Go to Step 6

6

Inspect the concentric slave cylinder operation. Refer to Symptoms - Manual Transmission in Clutch.

Is the clutch actuator operating properly?

Go to Step 8

Go to Step 7

7

Replace the concentric slave cylinder. Refer to Clutch Concentric Actuator Cylinder Replacement in Clutch.

Did you find and repair the condition?

System OK

Go to Step 8

8

  1. Remove the transmission. Refer to Transmission Replacement .
  2. Disassemble and inspect the transmission for a dented or damaged shift fork.

Is there a dented or damaged shift fork?

Go to Step 9

Go to Step 10

9

Disassemble and inspect the transmission for a incorrectly assembled or broken shift mechanism.

Is there a incorrectly assembled or broken shift mechanism?

System OK

Go to Step 10

10
  1. Replace the worn or damaged components as necessary. Refer to Transmission/Transaxle Unit Repair Manual.
  2. Install the transmission. Refer to Transmission Replacement .

Did you find and repair the condition?

Go to Step 11

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