Miscellaneous Systems Diagnosis and Repair
Core concepts
This domain covers parts outside the friction circuit: wheel bearings, parking brakes, and the electrical circuits that interact with braking. For tapered roller bearings, preload is set by the spindle nut and verified as endplay with a dial indicator - typically a few thousandths of an inch. A bearing that growls and changes tone in a turn is a classic wheel bearing symptom, and sealed hub assemblies are replaced as a unit, often with the speed sensor or tone ring built in. For parking brakes, know drum-in-hat designs, the star-wheel adjuster, the equalizer, and the correct order: adjust the shoes first, then the cables. Electrically, the red brake warning lamp is grounded through both the pressure-differential switch and the parking brake switch, and the brake light switch feeds the stop lamps, cruise control cancel, shift interlock, and ABS/traction inputs.
Traps
- Overtightening a wheel bearing to align a cotter pin destroys preload; align by loosening, or use the torque-plus-rotation method.
- A warning lamp with a good pedal is often low fluid, a stuck differential switch, or the parking brake switch - not a hydraulic failure.
- A misadjusted brake light switch can cause no-cruise, no-shift, or converter-clutch complaints.
- Parking brake drag after cable adjustment usually means the shoes or lever were never adjusted first.
Rule of thumb
Torque the spindle nut while spinning the wheel to seat the bearings, then measure endplay with a dial indicator. Out of spec means worn bearings, race, or spindle - not a reason to tighten further.