DESCRIPTION
The transfer case is used to provide power flow to the front axle. The transfer case also provides a means of disconnecting the front axle, providing for better fuel economy and, quieter operation when the vehicle is driven on improved roads where four wheel drive is not required. In addition, the transfer case provides for an additional gear reduction when placed in low range, which is useful when difficult off-road conditions are encountered.
A New Process Model 241 transfer case is used on all vehicles except K30 Models with dual rear wheels (RPO-R05). The K30 Model with dual rear wheels uses the Borg-Warner Models 1370 or 4470 transfer case.
All three models are aluminum case, chain driven units with four modes of operation: neutral, two wheel drive high range, four wheel drive high range, and four wheel drive low range. Gear reduction for low range is provided by a planetary gear set.
A floor mounted shift lever is used to select the operation range. Indicator lights on the floor console show the current mode of operation. When four wheel drive has been selected, the four wheel drive indicator light is designed to come on when the front axle has engaged. A slight delay for the front axle indicator light to come on is normal.
NORMAL OPERATION (2WD)
When the transfer case is in "2 WHEEL" range, torque flows from the input gear to the range shift hub and main shaft, through the drive shaft, to the rear axle. A switch in the shifter mechanism causes the "2 WHEEL" indicator light to turn on.
HIGH RANGE OPERATION (4WD)
Shifting into "4 HIGH" range causes the following to happen
- A switch in the shifter mechanism causes "2 WHEEL" indicator light to turn off and the "4 HIGH" indicator light to turn on. The front axle indicator light does not come on immediately.
- Torque flows from the input gear to the mainshaft the same as in "2 wheel" position. The shift linkage moves the mode synchronizer sleeve into engagement with the clutch teeth of the drive sprocket. This locks the drive sprocket to the mainshaft through the synchronizer sleeve.
- Torque is transmitted through the drive sprocket and drive chain to the driven sprocket and output shaft. Torque then flows through the front drive shaft to the front axle.
- The shift mechanism is the transfer case closes a switch. Current is then applied to the front axle thermal actuator.
- The terminal actuator contains a heating element, a gas charge, and a piston. When current is applied, the heating element heats the gas. The gas expands, pushing the piston out after a delay of a few seconds. The piston actuates the shift fork in the front axle. This connects the right axle output shaft to the front axle differential. Torque is then available at the front wheels.
- The front axle shift mechanism, when fully engaged, closes a switch, causing the front axle indicator light to come on.
- If the shift lever is moved back to "2 WHEEL" position, the operation in the preceding steps is reversed. The current to the thermal actuator is turned off. The gas cools, and the piston retracts, allowing the shift fork in the front axle to return to the two-wheel drive position.
LOW RANGE OPERATION (4WD)
- When the transfer case is shifted into "4 LOW" position torque flow and operation is similar to "4 HIGH" range, except that the range shift hub engages the planetary carrier. The planetary gear set then provides a gear reduction to both the front and rear axles.
- A switch in the shift mechanism causes the "4 HI" indicator light to turn off and the "4 LO" indicator light to turn on.
ELECTRONIC SYNCHRONIZER OPERATION (MODEL 1370 & 4470 ONLY)
The electronic synchronizer is used in model 1370 and 4470 transfer cases to provide smoother shifting. The system requires no maintenance or service.
The system consists of a relay and a clutch coil (electromagnet) inside the transfer case. The clutch coil replaces the conventional blocker ring. When energized, the clutch coil provides synchronization, resulting in a smooth shift. When the transfer case lever is moved to "4 HI" or "4 LO" position, current is supplied to the normally closed relay. (Схема №1) Current flows through the relay to the clutch coil. When the front axle engages, the axle switch energizes the relay coil. The relay switch then opens, and current to the clutch coil is interrupted.