Transfer Case Description and Operation: General Description

WARNING: This page is about a different car, the 2007 Isuzu i-370, 2007 GMC Canyon, and 2007 Chevrolet Colorado. However, it is still accessible from the selected car via links, so may be relevant.

Fig 1: Transfer Case

Courtesy of GENERAL MOTORS CORP.

IMPORTANT: To reduce range shift clunk noise while shifting, the transfer case has had design improvements over this model year to include an additional spring to the high/low shift shaft detent. This spring nests inside the existing spring and provides increased pressure on the detent ball; this increased pressure allows longer windup time for the spring in the actuator, therefore, allowing the shift to occur faster, reducing range shift clunk noise. Depending on the design level, this transfer case may or may not have this additional spring.

The Isuzu T150 transfer case is a 2 speed, part time 4WD with electric shift. A high/low planetary carrier assembly (100) provides the high and low ranges. The arrangement of the high/low planetary carrier assembly, which includes the 4 pinion gears (108), the sun gear - the outer teeth on the input shaft (105), and the annulus gear (117), gives a 2.48 low range reduction ratio. Using a synchronizer (220), the T150 provides the 4WD mode by connecting the drive sprocket (123) to the rear output shaft (124). The front output shaft (127) is chain (120) driven from the drive sprocket (123). The transfer case uses two shift shafts (250) operated by a single cam (262). The actuator assembly (200) rotates the cam (262) to the various ranges or modes. Detent springs (208) and balls (207) hold the shift shafts (250) in position.

The T150 case halves are cast aluminum. A needle bearing (113), in the planetary carrier assembly (100), supports the input shaft (105). A ball bearing (114), located in the front case half, supports the planetary carrier assembly (100). A needle bearing (103) is located inside the input shaft (105), to support the front of the rear output shaft (124). The rear output shaft (124) is supported at the rear by a ball bearing (130), located in the rear case half. The transfer case uses Synchromesh Transmission Fluid GM P/N 12345349 (Canadian P/N 10953465) as a service fluid. An oil pump (140) pumps the fluid through the oil gallery, in the rear output shaft, to the gears and bearings.