Buick Regal: Description and Operation

General

The differential carrier assembly is located in the rear subframe and the drive shafts extend from it to each respective rear wheel. The final drive gear consists of a hypoid gear and a differential. The assembly is bolted to the subframe with 4 bolts.

The splines-equipped pinion shaft for the final drive gear is directly inserted into the disc cage for the differential.

During manufacture the differential carrier assembly is filled with oil, which then does not require changing. The correct type of oil must be used without exception when filling. The incorrect type of oil may destroy the differential. The differential is fully mechanical.

Housing

The differential carrier assembly housing consists of two halves, a right and left-hand half, bolted to each other with 11 bolts. Their relative position is governed by two guide pins. Housing and cover are produced from a high-pressure cast aluminum alloy. A number of reinforcement ribs are fitted in suitable locations to strengthen the housing and cover. The mating face between them is sealed using sealant.

The left-hand half contains pinion, oil level plug, drain plug, air valve, bearing race for the final drive gear's left-hand bearing, stuffing box for sealing at the drive shaft lead-through. If the car is equipped with limited slip differential clutch then it is bolted to the left-hand half of the final drive gear.

The right-hand half contains bearing race for the final drive gear's right-hand bearing as well as stuffing box for sealing at the drive shaft lead-through.

Pinion

The pinion is fitted in the final drive gear's left-hand housing and cannot be replaced. It is mounted with two conical roller bearings, fitted towards each other. The bearing closest to the pinion gear absorbs forces that attempt to press the pinion gear from the crown wheel, while the farther bearing absorbs the forces that attempt to press the pinion gear into the crown wheel. The bearings have the correct preload by means of a nut fitted on the shaft being tightened until the correct bearing preload is obtained.

The pinion gear's gear contact to the crown wheel is governed by shims. A stuffing box in the front edge of the left-hand housing seals against the pinion shaft.

The pinion is matched together with the crown wheel.

Differential, assembly

The differential consists of a crown wheel and differential housing with associated gears. It is fitted in the left-hand half of the final drive gear housing. The crown wheel is laser welded to the differential housing.

The differential is made up of a forged housing, two differential gears and two drive shaft gears. The differential gears are mounted on a ground and hardened shaft journal, the ends of which are attached into the differential housing and locked by the crown wheel. The drive shaft gears are internally equipped with splines in which the drive shafts fit. Behind the gears, towards the differential housing, there is a spring-loaded thrust washer which provides the drive shaft gears with the correct gear contact to the differential gears. The drive shafts are mounted directly in the differential housing material, the lead-throughs are equipped with lubricating grooves.

The differential unit is mounted in two conical roller bearings. The bearings are given the correct preload at manufacture by means of shims being fitted behind the bearing races in the respective housing.

The function of the differential is to allow the outer wheel to rotate faster than the inner wheel when cornering.

LIMITED SLIP DIFFERENTIAL DESCRIPTION AND OPERATION

The limited slip differential clutch is bolted with 6 bolts to the left-hand side of the differential carrier. Their relative position is governed by 2 guide pins and a flange on the final drive gear.

Its function is to fully or partly lock the left-hand drive shaft to the differential housing. When this takes place wheel torque can be distributed between the rear wheels.

The limited slip differential clutch is a disc type, and it is electro-hydraulically controlled by the rear drive control module (RDCM) via a pressure control valve which is fitted on the limited slip differential clutch housing. The disc pack assembly consists of a hub, smooth steel driven plates with friction material, clutch cage, thrust bearing and journal bearing. The disc pack function is to steplessly distribute the torque between the rear wheels It consists of 9 driven plates connected to the hub. They are produced in steel and are smooth. Between the smooth steel driven plates are 8 steel discs equipped with friction material.

The disc pack is compressed by means of an operating piston. On the rear of the piston a variable oil pressure (0 - 30 bar, 0 - 3000 kPa) acts via the pressure control valve which is controlled by the RDCM.

For cooling and lubrication of the disc pack the hub is equipped with 3 longitudinal oil ducts. They are supplied with oil from a chamber in connection with differential carrier. The oil is led through the ducts to the center of the disc pack and is thrown out through the driven plates when they rotate.

REAR DRIVE AXLE DESCRIPTION AND OPERATION

B5RR - B5RR Wheel Speed Sensor - Right Rear
B5LR - B5LR Wheel Speed Sensor - Left Rear
B5RF - B5RF Wheel Speed Sensor - Right Front
B5LF - B5LF Wheel Speed Sensor - Left Front
K17 - K17 Electronic Brake Control Module
K47 - K47 Rear Differential Clutch Control Module
K20 - K20 Engine Control Module
B99 - B99 Steering Wheel Angle Sensor
M32 - M32 Differential Clutch Pump
Q49 - Q49 Rear Differential Clutch Solenoid Valve
S48E - S48E Multifunction Switch - Center Console

The rear differential clutch control modules function is to control the electronic limited slip differential. The rear differential control module receives a torque command signal from the chassis control module (CCM) according to the driving situation to achieve vehicle dynamics and traction.

The electronic limited slip differential system contains the following main components:

• The rear differential clutch control module
• The differential clutch pump
• The left and right rear differential clutch solenoid valves
• The rear differential clutch motor
• The left and right rear differential multi-disc wet clutches

When the torque signal is received, the rear differential control module actuates the following components:

• Differential clutch pump
• The left and right rear differential clutch solenoid valves

The electro-hydraulic piston actuation engages the left or right limited slip clutch to allow active variable locking torque transfer to the left and right half shafts. to enable torque vectoring and to allow cornering with differential.

The rear differential clutch control module monitors voltage levels, clutch temperatures, over-current, and circuit failures.

Whenever the hydraulic control system within the electronic limited slip differential system is opened, a service bleed procedure with a scan tool needs to be performed to remove any air from the system.

If replacing the rear drive clutch control module, the module needs to be programmed/configured with a rear differential clutch service calibration value. The clutch calibration service value is an alphanumeric value that is stored in the rear differential clutch control module and stamped on the rear differential clutch pack housings. The clutch classification value is based on the valve current-to-torque performance of the individual clutch pack. The clutch classification helps to improve vehicle performance by adjusting software parameters to suit the mechanical hardware.

Configuring the rear differential clutch control module with the clutch classification value might be required after certain service procedures are performed. Two eight digit values will be used during the programming of the rear differential clutch control module using the scan tool.

SPECIAL TOOLS AND EQUIPMENT

SPECIAL TOOLS

DT-49126-1

Press Tool

DT-49126-2

Press Tool

DT-51592

Seal Installer

J-45000

EN-45000

Seal Remover

J-24428 - A

Pinion Seal Installer

J-45725-A

Frame Bushing Installer

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