K 3500 Truck 4WD V8-454 7.4L VIN J SFI (1996)
Main Shaft: Customer Interest
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.
