Transfer Case - Hops Out of 4H, No Drive in 2 or 4H

File In Section: 7 - Transmission

Bulletin No.: 66-74-06

Date: December, 1996

Subject:
Transfer Case Hops Out of 4-High, or No Drive in 2 or 4-High Ranges and/or Grinding Noise (Install Mainshaft/Range Hub Kit)

Models:
1989-96 Chevrolet and GMC K3 Models with Borg-Warner 1370, 4401 or 4470 Transfer Case

Condition

Some owners may report the transfer case hops out of 4 high range or, no drive in 2 or 4 high ranges and/or makes a grinding noise.

Cause

Marginal lubrication of the range fork. An additional cause in the 4470 model transfer case may be a damaged oil pump assembly.

Correction

Install a revised main shaft/range hub assembly (shaft kit). The revised main shaft is drilled to provide pressurized oil to the range fork/range hub area and, the range hub has had two opposing internal splines removed to provide a path for pressurized oil flow to the range fork. If the range fork shows signs of wear, it should also be replaced.





Notice:
When assembling the range hub to the main shaft, be certain to align the oil hole in the shaft with one of the missing spline slots in the range hub (Figure 2). Improper alignment may result in early fork wear-out.





Inspect the oil pump on 4470 model transfer cases. This pump is driven by the main shaft using a flat. The pump should be inspected for the presence of this flat (Figure 1). It this flat is missing, the pump should be replaced.

Service Procedure





For transfer case removal and replacement procedure refer to the appropriate C/K Service Manual, Section 7D, Transfer Case Replacement. Refer to the appropriate Light Duty Truck Unit Repair Manual for shift detent lever adjustment.

The following parts must be replaced when repairing the transfer case:

^ Speedometer tone wheel

^ Yoke nut (fixed yoke models only)

^ Spline seal (fixed yoke models only)





Parts Information

Parts are currently available from GMSPO.

Warranty Information

For vehicles repaired under warranty, use:

Labor Op Description Labor Time

Transfer Case Use Published
K4400 Assembly - Labor Operation
Recondition Time

Important:
Labor operation is coded to base vehicle coverage in the warranty system.