Transfer Case Description Selectable 4WD

The transfer case is used to provide power flow from the transmission to the front axle. The transfer case also provides a way of disconnecting the front axle in order to provide better fuel economy and quieter operation when the vehicle is driven on the roads where the four-wheel drive is not required. The transfer case provides an additional gear reduction when placed in low range. This is useful when difficult off-road conditions are encountered.

The New Venture Gear Models NV241 or NV243 transfer case is used on all of the four-wheel drive vehicles under 9200 lb GVW. The NV243 is similar to the NV241 except that it contains an electric shift motor/encoder attached to the transfer case in the area where the shift lever is ordinarily mounted.

The K30 Models with single or dual rear wheels will use the Borg-Warner Models 4401 or 4470 transfer case. Both of these transfer cases use a shift lever and a shift linkage in order to change the operating range.

The Models NV241, 4401, and 4470 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. The gear reduction for low range is provided by a planetary gear set.

A floor mounted shift lever is used in order to select the operating range for the NV241, the 4401, and the 4470. The indicator lamps on the floor console show the current mode of operation. When four-wheel drive indicator lamp is designed to come ON whenever the front axle has engaged. A slight delay for the front axle indicator lamp to come ON is normal.

The New Venture Gear Model NV243 is electronically actuated. The vehicles equipped with this model have no transfer case selector lever. The operator selects 2HI, 4HI, or 4LO by pushing one of three switches mounted on the instrument panel. During normal driving the transfer case is in the 2HI mode. When the transfer case is in 2HI both the 4HI and the 4LO switch circuits are open, and both lights are OFF. When the four-wheel drive has been selected, the four-wheel drive indicator lamp on the switch turns on when the front axle has engaged. The lamp will blink while the front axle is engaging. For more information on the electrical operation of the NV243, refer to Transfer Case System Description (Selectable 4WD) .

When the transfer case is in the 2 WHEEL range, the torque flows from the input gear to the range shift hub and the main shaft, through the propeller shaft to the rear axle.

Important: Shifting into the 4HI range causes the following conditions to occur.

1. The front axle indicator lamp does not come on until the front axle engages.
2. The torque flows from the input gear to the mainshaft the same as in the two-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.

3. The torque is transmitted through the drive sprocket and the drive chain to the driven sprocket and the output shaft. The torque then flows through the front propeller shaft to the front axle.
4. The shift mechanism in the transfer case closes the transfer case switch.

The current is then applied to the front axle electromechanical actuator and the front axle switch. In the K30 vehicles, the power is also supplied by the transfer case relay to the transfer case synchronizer.

5. The front axle shift mechanism, when fully engaged, closes a switch, causing the front axle indicator lamp to come ON.

When the transfer case is shifted into the 4LO position, the torque flow and the operation is similar to the 4HI range, except that the range shift hub engages the planetary carrier. The planetary gear set then provides a gear reduction to the front and the rear axles.

The electronic synchronizer is used in model 4401 and 4470 transfer cases in order 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 4HI or 4LO position, the current is supplied to the normally closed relay. The 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 the current to the clutch coil is interrupted.

For New Venture Gear Transfer Cases, an identification tag is attached to the rear case half. The tag provides the transfer case model number, the low range reduction ratio, and the assembly part number.

For the Borg-Warner Transfer Cases, an identification tag is attached to an extension housing bolt. The tag provides the transfer case model number, the serial number, a build date, and a low range reduction ratio.