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 bottom of the transfer case. Refer to the table below for additional Build Variation information.

Transfer Case Build Variations

For 2010 model year the Cadillac SRX was built with multiple versions of the transfer case. 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 press-on clamp-retained 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.









The transfer case oil drain plug (1) of the AM-TE-PTU is located at the bottom of the assembly to the right side of the rear output shaft.

General





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.





During manufacture the transfer case (1) is filled with oil, which then does not require service interval replacement. The correct type of oil must be used without exception when filling. The incorrect type of oil could leads to transfer case damage. Refer to Adhesives, Fluids, Lubricants, and Sealers (Fluid Type Specifications).

Housing and Cover





The transfer case housing and rear extension housing (2) are produced from a high-pressure cast aluminium alloy. A number of reinforcement ribs are fitted in suitable locations to strengthen the transfer case housing (1). 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 extension housing to the transfer case housing. The mating surfaces of transfer case housing and rear extension housing are sealed by a press-in-place serviceable seal.





The transfer case assembly is bolted to the transmission with four transfer case bolts. For RPO MXE applications, one of the transfer case mounting bolts is accessible via an access hole in the center of the assembly. 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 there is a weep hole in the transfer case housing between the radial seals.





A transfer case vent (1) is located on the top area of the transfer case housing. The vent is mated to a remote vent hose assembly that is routed into the engine compartment. The oil drain plug (2) is magnetic. A mounting bracket retains the output end of the rear extension housing to the engine assembly. Inside the transfer case housing and rear extension housing are tapered bearing races for the input shaft and the idler shaft. Behind the bearing races are shims to provide the correct bearing preload.





There are tapered bearing races (1) in the transfer case housing and rear extension housing (2) for the input shaft and idler shaft. There is an intermediate shaft bearing (3) located in the rear extension housing. The oil fill plug is fitted in the cover.

The transfer case rear extension housing has an extension through which the intermediate shaft for the right-hand front wheel runs. The extension serves partly as a holder for the intermediate shaft bearing and also as an attachment point for the transfer case to the engine. The intermediate shaft support bearing is a single-row sealed permanently-lubricated groove ball bearing and is retained to the intermediate shaft via retaining rings.





A double lip type radial seal (1) is fitted in the rear extension housing at the input shaft to ensure oil from the transfer case does not seep out of the rear extension housing.

Input Shaft





The function of the input shaft (3) is to transfer power from the transfer case. In one end the shaft is equipped with splines which are inserted into the transmission differential housing. The rotational speed of the input shaft is the same as the transmission output. Fitted in the transfer case housing are two opposite radial seals (5). The two input shaft 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 end of the input shaft is sealed by a double-lip seal that is installed into the rear extension housing. A second seal, the intermediate shaft seal is installed into the output end of the rear extension housing. The intermediate shaft seal is designed to restrict oil, dirt and debris from entering the transfer case.

The helical gear teeth of the input shaft 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 at manufacture by means of shims being fitted behind the bearing races in the housing and cover.

Idler Shaft





The idler shaft is located under the input shaft and is driven by the helical gear on the input shaft. The idler shaft has a relatively large diameter and is hollow.

The idler shaft consists of a helical gear (2) and a hypoid gear (3). The helical gear is driven by the helical gear of the input shaft. In turn the idler shaft hypoid gear mates to the hypoid gear on the rear output shaft. The idler shaft and rear output shaft gear set are matched to each other.

The idler shaft is mounted in two tapered roller bearings (1, 4). The bearings are given the correct preload at manufacture by means of shims being fitted behind the bearing races in housing and cover.

For RPO-MXE applications, there is an additional idler shaft located inside the idler gear. The idler shaft is sealed at each end by O-ring seals within the transfer case and rear extension housings.

Rear Output Shaft Flange





The rear output shaft housing assembly includes an output shaft, 2 tapered roller bearings, a rear output shaft seal (1), shaft retaining nut, housing and housing seal.

The hypoid gear of the rear output shaft is mated to the hypoid gear of the idler shaft. A shim maintains the proper gear contact.

The housing is retained to the transfer case by 7 bolts.

The only serviceable component within the assembly is the rear output shaft seal (1). The seal is a unitized/cassette type design to include inner and outer metal sleeves and internal sealing rings.