Description and operating principle of the transfer case (Defender 2007+)

Arrangement of elements

Pos.	Spare part number	Name
1	-	Rear axle drive shaft housing
2	-	Main crankcase
3	-	Transfer case selector lever
4	-	Ventilation duct
5	-	Front axle drive shaft housing
6	-	Selector housing

Transfer case cross section

Pos.	Spare part number	Name
1	-	Main crankcase
2	-	Front axle drive shaft housing
3	-	Rear axle drive shaft housing
4	-	Cam clutch
5	-	Transmission brake
6	-	Secondary shaft drive gear
7	-	Selective adjusting shim for setting the preload of the pinion bearing
8	-	Intermediate gear block
9	-	Intermediate shaft
10	-	Spacer
11	-	Differential assembly
12	-	Selective differential bearing preload adjusting shim
13	-	Low range gear
14	-	High/Low Range Selector Bushing and Hub
15	-	High Range Gear and Bushing
16	-	Rear differential bearing
17	-	Front axle drive shaft
18	-	Differential lock selector shaft
19	-	Selector fork
20	-	Rear axle drive shaft

Review

The transfer case serves the operation of the permanent all-wheel drive, provides a two-stage gear reduction, combines the outputs of the high and low ranges with a mechanically locked central differential ("diff-lock" mode). The high range is characterized by a gear ratio of 1.211:1 and the low range is 3.269:1.

Selection of high or low range, as well as diff-lock mode, is accomplished using a single lever located near the main gearshift lever.

The transfer case is mounted at the rear of the main gearbox and transmits power to the front and rear axle differentials via cardan shafts.

The differential unit is integrated with the drive shafts, which compensates for the difference in speed between the front and rear drive shafts. To improve traction and prevent all power from being transferred to the differential of the drive axle in order to add even the slightest traction, a "diff-lock" mode is provided. The "diff-lock" mode should only be engaged in severe off-road conditions when traction is low. It should be disengaged as soon as possible, for example when it becomes possible to develop a sufficiently high traction force. Engaging the differential lock initiates mechanical engagement of the cam clutch on the front drive shaft, which locks the center differential and provides a fixed drive, thanks to which the front and rear drive shafts are transferred the same power.

The transfer case contains 3 main units:

• Main crankcase
• Front axle drive shaft housing
• Rear axle drive shaft housing

All housings and covers are sealed on the main crankcase with a sealant. The rotary seals of the outlet flange are protected from dirt and water by special reflectors.

Main crankcase

Pos.	Spare part number	Name
1	-	Main crankcase
2	-	Lock washer
3	-	Lock plate bolt
4	-	Screw (with punching locking) intermediate shaft
5	-	Bearings and outer bearing rings of the secondary shaft drive gear
6	-	Secondary shaft drive gear
7	-	Selective adjustment shim
8	-	Secondary shaft drive gear bearing housing
9	-	Cover/Power take-off box cover
10	-	Cap bolt
11	-	Oil temperature switch (if it is installed)
12	-	Bearings and outer bearing rings of intermediate gears
13	-	Crumple spacer
14	-	Intermediate gears
15	-	Bottom cover
16	-	Bottom cover bolt
17	-	Intermediate shaft sealing rings
18	-	Intermediate shaft
19	-	Secondary shaft oil seal
20	-	Dowel pin
21	-	High/Low Range Selector Locking Plug
22	-	High/Low Range Selector Locking Spring
23	-	High/Low Range Selector Locking Ball

The main crankcase carries:

• secondary shaft drive gear
• intermediate gears
• interaxle differential assembly

The front and rear axle drive shaft housings are bolted to each side of the main crankcase.

Secondary shaft drive gear

The secondary shaft of the gearbox has a splined connection with the secondary shaft pinion, which is supported by tapered roller bearings.

The preload of the pinion bearing is provided by means of a selective adjustment lining located in the bearing housing.

Intermediate gears

The intermediate gear block is supported by tapered roller bearings located at each end of the block and seated on an intermediate shaft, which in turn is supported at the front and rear by the main housing.

The intermediate gear bearing preload is provided by a deformable spacer element located between the bearings. The compression force applied to the spacer element is created by a nut located at the end of the intermediate shaft.

To install the bearings, the diameter of the intermediate gear hole on each side is machined with a step.

Interaxle differential assembly

Pos.	Spare part number	Name
1	-	Retaining ring
2	-	Differential Cup - Rear Section
3	-	Low range gear
4	-	High/Low Range Hub
5	-	High/Low Range Selector Sleeve
6	-	High/Low Range Selector Shaft
7	-	High/Low Range Selector Fork
8	-	High/Low Range Selector Fork Set Screw
9	-	High range gear
10	-	High Range Gear Bushing
11	-	Rear differential bearing
12	-	Outer bearing ring
13	-	Bearing fastening nut
14	-	Plate Thrust Washers
15	-	Planetary gears of differential
16	-	Axles
17	-	Bevel gears of semi-axles
18	-	Selective thrust washers
19	-	Differential Cup - Front Section
20	-	Differential cup bolt
21	-	Front differential bearing
22	-	Outer bearing ring
23	-	Selective adjustment shim

The center differential assembly is supported by tapered roller bearings at the front and rear; the outer race of the front bearing is located in the front axle drive shaft housing, and the outer race of the rear bearing is located in the main crankcase near the rear axle drive shaft housing. Bearing preload is provided by means of a selectively selected adjusting shim located in the front axle drive shaft housing.

The rear shaft of the center differential contains the low range gear, the high/low range selector sleeve and hub, the high range gear and sleeve, and the rear differential bearing. These elements are secured to the shaft with a special nut.

The differential assembly comprises front and rear cup sections with integral axles connected to the bevel gears of the half-shafts and satellites mounted on the axles in the cup sections. Non-selectively matched plate thrust washers control the engagement of the satellites with the bevel gears of the half-shafts, while selectively matched thrust washers are used to control the engagement of the bevel gears of the half-shafts and the torque required to turn the differential. The differential cup sections are bolted together. A retaining ring ensures the precise positioning of the axles.

The high/low range selector shaft and fork are located on the side of the differential. Movement of the shaft, fork and selector sleeve is controlled by the high/low range selector pin. A spring-loaded detent ball mounted in the main housing is located in grooves on the shaft.



The selector fork is spring-loaded and equipped with clamps that reduce the effort required to move the selector lever.

Front axle drive shaft housing

Pos.	Spare part number	Name
1	-	Hollow plug
2	-	High/Low Range Cross Shaft Housing
3	-	High/Low Range Cross Shaft Housing Bolt
4	-	O-ring seal
5	-	High/low range cross shaft and cable ball end lever
6	-	Cam clutch
7	-	Front axle drive shaft
8	-	Differential lock selector shaft
9	-	Front axle drive shaft housing
10	-	Differential lock spring and clamps
11	-	Cap bolt
12	-	Lid
13	-	Differential lock selector fork
14	-	Differential locking device retaining plug and spring
15	-	Differential locking device locking ball
16	-	Front axle drive shaft housing bolt
17	-	Plug
18	-	Retaining ring
19	-	Drive shaft flange and mudguard
20	-	Steel washer
21	-	Self-locking nut
22	-	Felt pad
23	-	Seal
24	-	Drive shaft bearing
25	-	Bearing spacer
26	-	High/Low Range Selector Finger
27	-	Differential lock indicator switch
28	-	Differential lock selector pin and shaft
29	-	O-ring seals
30	-	Differential lock selector housing
31	-	Selector
32	-	Housing bolt
33	-	Washer
34	-	Self-locking nut

The front axle drive shaft housing carries:

• front axle drive shaft and flange
• housing and selector
• fork and shaft of the differential lock selector

The front axle drive shaft is supported in the housing by a single bearing and is splined to the differential front sun gear.

Housing and selector assembly

The high/low range cross shaft is located in a housing which is bolted to the top of the drive shaft housing and connects to the high/low range pin which is located in a groove in the selector shaft.

Fork and shaft of the differential lock selector

The differential lock selector housing is bolted to the top of the front drive shaft housing. The selector pin passes through the housing and is located in a groove in the differential lock selector shaft. The differential lock selector shaft passes through the selector fork, which is located below a plate bolted to the side of the drive shaft housing. When the keys of the sleeve and the rear differential shaft are aligned with each other, the selector fork engages the cam clutch sleeve with the rear differential shaft. A spring-loaded detent ball mounted in the drive shaft housing is located in grooves on the shaft.

Rear axle drive shaft housing

Pos.	Spare part number	Name
1	-	Rear axle drive shaft
2	-	Rear axle drive shaft housing
3	-	Rear axle drive shaft housing bolt
4	-	Speedometer pinion
5	-	Spacer
6	-	Drive shaft bearing
7	-	Retaining ring
8	-	Seal
9	-	Mudguard
10	-	Drive shaft flange
11	-	Felt pad
12	-	Steel washer
13	-	Self-locking nut
14	-	Transmission brake shield
15	-	Transmission brake shield bolt
16	-	Transmission brake drum
17	-	Countersunk head screw
18	-	Speedometer driven gear
19	-	O-ring seal
20	-	Speedometer driven gear housing
21	-	Pad
22	-	O-ring seal
23	-	Vehicle speed sensor (if it is installed)
24	-	Hexagon socket head cap screw (if available)

The rear axle drive shaft housing contains the rear axle drive shaft and flange, as well as the drive and driven gears of the speedometer. A transmission brake with a mechanical drive is connected to the housing, where the brake drum is attached to the output flange.

The rear axle drive shaft is supported in the corresponding housing by a single bearing and has a splined connection with the rear shaft of the differential. The drive shaft also contains a speedometer drive gear, which is in engagement with the speedometer driven gear located in the housing of the rear axle drive shaft.

The switch for the differential lock indicator lamp, activated by movement of the fork and selector shaft, is screwed into the upper part of the drive shaft housing.

Lubrication

Lubrication is provided by splash, filler/inspection plugs and drain plug are located in the main body.

The increase in internal pressure caused by thermal expansion and contraction is avoided by using a plastic vent pipe, through which gases from the internal volume of the box are discharged to the atmosphere. This pipe is connected to the upper part of the high/low range selector housing and, rising continuously upwards, passes to the engine compartment, where its open end is attached to the engine cylinder block.

Job

Power Flow - Transfer Case in LOW Range



Power Flow - Transfer Case in HIGH Range



The transmission drive shaft transmits power to the secondary shaft pinion, which is in constant engagement with one of the intermediate gears. The intermediate gears are in constant engagement with the high and low range output gears, which are located on the rear differential shaft.

Power is transmitted to the drive shafts via the differential assembly by locking the high or low range gears to the rear differential shaft. This is accomplished via the high/low range selector fork, sleeve and splined hub.