TM  10-3930-643-34 BRAKE  TROUBLESHOOTING  AND  MAINTENANCE. 8-2. Parking Brake Troubleshooting. MALFUNCTION TEST  OR  INSPECTION CORRECTIVE  ACTION a. PARKING BRAKE DRAGS. Step 1. Check for low air pressure and check lines for restrictions. If restriction is found, check for damage. Repair or replace, if necessary. Step 2. If parking brakes do not apply, check linkage. Adjust  linkage,  refer  to  TM  10-3930-643-20. Step 3. Replace return springs,   refer to paragraph 8-16. b. PARKING BRAKE SLIPS. Apply  parking  brake. With  engine  running  and  transmission  in  the forward third gear position, fully accelerate engine. If vehicle moves and parking brake is properly adjusted, check for oil on linings or worn linings. If linings are worn below 1/8”, replace brake shoe assembly, refer to paragraph 8-16. 8-5