Parking Brake System: Service and Repair

WARNING: Do not use an air line to remove dust from the brake assembly. Asbestos dust from the brake linings can be a serious health risk, if inhaled.

DISMANTLING
1. Disconnect the battery negative terminal and chock the road wheels for safety. Release the parking brake, select P in main gearbox and release the parking brake.
2. Disconnect the drive shaft from the output flange.
3. Loosen off the brake adjuster, remove the two screws and withdraw the brake drum. inspect the friction surface of the drum, turn if excessively scored or oval.

NOTE: If drum requires skimming the maximum diameter is 255.65 mm (10.06 in).

4. Remove the cotter pin and clevis pin connecting the parking brake inner cable to the brake actuating lever.
5. Remove the brake shoes complete with pull-off springs. Note position of springs in relation to the shoes.
6. Remove the four bolts securing back plate to transfer box and withdraw the back plate complete with oil catcher.

Remove And Overhaul Expander Assembly
7. Remove the rubber dust cover.





8. Remove the expander and drawlink.
9. Remove the retainer spring plate.
10. Remove the locking plate.
11. Remove the packing plate and withdraw the expander assembly from the back plate.
12. Remove the two plungers and rollers.
13. Clean all parts in aerosol brake cleaner and allow to dry. Examine the components for wear and discard if unsatisfactory.

Assemble Expander Assembly
14. Grease and fit the expander and drawlink.
15. Grease and fit the plungers and rollers, fitting the plungers with the highest end of the roller groove towards the backplate.

Remove And Overhaul Adjuster Assembly





16. Remove the two bolts and withdraw the adjuster assembly from the back plate.





17. Remove the plungers.
18. Screw the adjuster cone inwards to remove from the housing.
19. Thoroughly clean the parts in aerosol brake cleaner and discard any unsatisfactory components.

Assemble Adjuster Assembly
20. Grease and screw in the adjuster cone.

21. Grease and fit the adjuster plungers and align the chamfered ends with the adjuster cone. Note that the two plungers are identical and can be fitted to either bore. Secure the assembly with a rubber band to prevent the plungers falling out.

ASSEMBLE

NOTE: If the brake linings are oil-soaked, fit new brake shoes. Check and if necessary fit a new output shaft oil seal.

1. Position the expander assembly on the inside of the back plate and secure with the following plates at the rear of the back plate.
2. Spring plate.
3. Locking plate.
4. Packing plate.
5. Fit the rubber dust cover.
6. Fit the adjuster assembly to the back plate with the two bolts but do not fully tighten at this stage.
7. Fit the back plate assembly and oil catcher to the transfer box with the four bolts and tighten.





8. Fit new pull-off springs(29) to the brake shoes and fit to the back plate.

NOTE: The fully lined end of the lower shoe must be toward the expander assembly and the fully lined end of the upper shoe towards the adjuster assembly.

9. Fit the brake drum and tighten the two screws.
10. Connect the actuating lever to the inner parking brake cable using a new clevis pin, washer and cotter pin.
11. Turn the adjuster cone fully in and tighten the two retaining bolts left loose in instruction 6.
12. Loose off the adjuster two clicks and firmly apply and release the parking brake lever to centralize the shoes. The drum should then rotate freely.
13. Adjust the parking brake cable lock nuts until the parking brake lever is fully operational on the second or third notch of the parking brake rachet.
14. Connect the drive shaft and evenly tighten the retaining nuts.
15. Remove chocks from wheels and connect the battery.