Transfer Case Description and Operation

Transfer Case Description and Operation

Transfer Case Identification





The build variation of transfer case can be identified by the assembly part number (1) located on the rear output shaft housing of the transfer case. Refer to the table below for additional Build Variation information.

Transfer Case Build Variations

Early 2010 model year vehicles were built with either first or second design Graziano supplied assemblies. First design Graziano transfer cases have a pressed into the housing vent assembly. Second design Graziano transfer cases have a bolt-in remote vent hose assembly. Vehicles built later in 2010 model year were produced with one of two versions of the American Axle Manufacturing (AAM) supplied transfer case based on engine and transmission configuration. Both the AAM transfer cases have a bolt-in remote vent hose assembly. The table below will help you to understand the brand of transfer case and content within. It is important to understand which variation is being serviced because of the different internal and external components and service parts for each. The AAM assembly can be used to replace an earlier design Graziano assembly providing the correct ventilation components are also used.






General Transfer Case Identification





The transfer case (1) is positioned in the right side of the vehicle and bolted to the transmission. Its primary function is to receive power from the transmission and transfer it using helical and hypoid gear sets to the rear differential via the propeller shaft. The internal intermediate shaft transfers power to the right-side front wheel.





The transfer case (1) is fully mechanical with no internal or external electronic controls or sensors.





During assembly the transfer case (1) is filled with oil, which then does not require service interval replacement. The correct type of oil must be used when filling. The incorrect type of oil could lead to transfer case damage.

Housing and Cover





The transfer case oil drain plug (1) is located at the front of the assembly.





The transfer case housing (1) and rear extension housing (2) are produced from a high-pressure cast aluminum alloy. A number of reinforcement ribs are fitted in suitable locations to strengthen the transfer case assembly. These reinforcement ribs constitute a vital part of the cooling for the transfer case. The transfer case rear extension housing is retained to the transfer case housing with bolts (3). Two dowel pins locate the rear extension housing to the transfer case housing. The mating surfaces of transfer case housing and rear extension housing are sealed by RTV type sealant.





The transfer case assembly is bolted to the transmission with four transfer case bolts. A locating bushing (2) on the transfer case housing ensures correct installation position. The sealing area between the transfer case housing and the transmission is sealed with serviceable O-ring (1). Two opposite radial seals seal the input shaft and prevent transmission and transfer case oil from mixing. If an input shaft seal failure occurs, the transmission and transfer case fluids will not mix as there is a weep hole in the transfer case housing between the two radial seals.





A transfer case vent (2) is located on the top area of the transfer case housing. First design Graziano transfer cases have a pressed into the housing vent assembly. Second design Graziano transfer cases have a bolt-in remote vent hose assembly. Second design vent hose assemblies are routed to vent into the engine compartment. The oil drain plug (1) is magnetic. A mounting bracket retains the output end of the rear extension housing to the engine assembly.





There are tapered bearing races (1) in the transfer case housing and rear extension housing (2) for the input shaft and idler shaft. Gear tooth clearances and bearing preloads are maintained by shims located behind the bearing races. There is a sealed ball bearing type intermediate shaft bearing (3) located in the rear extension housing.

The rear extension housing serves partly as a holder for the intermediate shaft bearing (3) and also as an attachment point for the transfer case to the engine.

Input Shaft





The input shaft splines (6) are mated to and driven by the transmission differential housing. The rotational speed of the input shaft is the same as the transmission output. Installed into the transfer case housing are two opposing input shaft front seals (5). The two input shaft front seals are designed to restrict transmission oil from entering the transfer case as well as restrict transfer case oil from entering the transmission. The opposite or rear end of the input shaft is sealed by the intermediate shaft seal (1)

The intermediate shaft seal (1) is installed into the output end of the rear extension housing and is designed to restrict oil, dirt, and debris from entering the transfer case. The helical gear teeth of the input shaft (3) are engaged to the helical gear teeth of the idler shaft. The input shaft is mounted in two tapered roller bearings (2,4). The bearings are given the correct preload during assembly by means of shims being fitted behind the bearing races in the housing and cover.

Idler Shaft





The idler gear consists of a helical gear (2) and a hypoid gear (3), has a hollow center, and is driven by the helical gear on the input shaft.

The idler hypoid gear (3) mates to and drives the hypoid gear on the rear output shaft. The input shaft, idler gear, and rear output shaft gear sets are precision machined and are not serviceable.

The idler gear is mounted in two tapered roller bearings (1 and 4). The bearings are given the correct preload and gears proper clearance during assembly by means of shims being fitted behind the bearing races in the housing and cover. If the shims are removed for any reason, the shims need to be reinstalled to their original locations.

Rear Output Shaft Flange





The rear output shaft housing (2) is bolted to the transfer case housing with 7 bolts (1) and is sealed to the transfer case housing with a serviceable O-ring (4) seal. A shim (3) adjusts the rear output shaft helical gear clearance to the helical gear of the idler shaft. The rear output shaft flange is hollow and is equipped with internal splines. The splines of the propeller shaft are mated to the rear output shaft. The spline of the propeller shaft is equipped with a spring-loaded retaining ring which retains the propeller shaft in the rear output shaft flange.