U.S. ARMY ORDNANCE AND CHEMICAL CENTER
AND SCHOOL
ABERDEEN PROVING GROUND, MARYLAND 21005
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TROUBLESHOOTING CLUTCHES ON WHEELED VEHICLES AND ADJUSTING CLUTCH LINKAGE
TRUCK, 1/4 TON, M1S1 SERIES
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JOB AID NO. 610-091-6086-J
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3AUDIENCE:
•	Applicable to 63B (Wheeled Vehicle Mechanic), 63C (Tracked Vehicle Mechanic) and 63H (Automotive Repairman).
OBJECTIVES:
•	Inspect and adjust clutch pedal free travel.
•	Inspect clutch action.
•	Determine how to deal with clutch problems.
MATERIALS REQUIRED:
•	1/4 ton truck M151 series
•	Wheel chocks
•	General mechanic’s tool kit
•	Wooden block 3-5 inches thick
•	DA Form 2404
•	Pencil
TIME:
•	45 minutes
REFERENCES:
•	TM 9-2320-218-20, dated SEP 71, table 2-2, table 2-3, and paragraph 2-41.
GENERAL INSTRUCTIONS:
•	When you use this job aid, be sure to complete the steps in order. Skip steps only when the directions tell you. If you have difficulty with any of the steps during the process, see your supervisor.
PREREQUISITES:
•	Must be able to operate the 11A ton truck.
•	Should be familiar with the principles of operation of dry disk clutches.OVERVIEW
This job aid has been developed as a guide. It will show you how to inspect and troubleshoot clutches on wheeled vehicles and adjust clutch linkages on M151 series vehicles or those equipped with disk clutches.
These troubleshooting and adjustment tasks are designed to check the operation of the clutch. An improperly adjusted clutch can result in slippage, worn parts, and major repairs.
For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402
2REFERENCE PAGE
You will be working with these parts of the 114 ton vehicle. Locate them in the vehicle before beginning your troubleshooting tasks.Before You Begin
Perform safety steps:
1.	Extinguish smoking materials.
2.	Remove jewelry.
3.	Set parking brake.
4.	Shift transmission into neutral.
5.	Block wheels.Place wooden block directly under clutch pedal. Block should be at least 3 to 5 inches thick.2.	Place ruler on block. Make sure ruler reaches the clutch pedal.Push in clutch pedal:
3.	Use hand to push in pedal.
4.	Stop when you feel pressure and hold clutch pedal steady in that position.Measure travel distance:
5.	Measure the distance the clutch pedal moved before you felt the pressure.
•	If measurement is between
1 1 /8”-1 112", skip to “Inspecting Action” page 15.
•	If measurement is not between
1 1 /8”-1 112”, go on to the next page.Adjusting Clutch Pedal Free Travel
RETURN
SPRING
CLUTCH
ROD
Disconnect clutch pedal return spring:
1.	Use pliers for this task.
2.	Push spring towards the rear to disconnect it.3.	Disconnect clutch rod from lever.4.	Adjust clutch pedal free travel:
•	If travel distance of the clutch pedal free travel needs to be shortened, turn the clutch rod court terclock wise.
•	If travel distance of the clutch pedal free travel needs to be lengthened, turn the clutch rod
clockwise.
NOTE: Travel distance is changed approximately 11A of an inch with each complete turn of the clutch rod.5.	Return clutch rod to lever.
•	Do not attach spring at this time.Remeasure clutch pedal free travel:
6.	Since the spring is still not connected, lift the pedal as high as it will go.
7.	Push in clutch pedal until you feel pressure.
8.	Measure the distance the pedal traveled between the up position and the point of pressure. Use the block and ruler.
•	Remember, measurement must be between 1 1/8”-1 1/2”.
9.	Continue adjustment until correct measurement is reached.10.	Reconnect clutch spring. The spring may be very difficult to reconnect.
MAY BE DIFFICULT TO CONNECT
BRACKET
NOTE: It may be easier to hook spring and rod first, and then connect the spring to the bracket.INSPECTING CLUTCH ACTION Before You Begin
REMOVE
1.	Close hood and unblock wheels.Start engine:
2.	Let engine warm up until it reaches normal operating temperature.Clutch Release Bearing
Inspect clutch release bearing (throw-out bearing):
1.	Push in clutch pedal.
2.	Listen for grinding or squealing noises.
NOTE: If you hear noises, this indicates that the clutch release bearing may be defective. Note on DA Form 2404.Inspect return spring and linkage:
1.	Push in clutch pedal.
2.	Release clutch pedal.
3.	Lift up on clutch pedal with toe.
NOTE: If clutch lifts up farther, the return spring is weak. Replace spring if one is in stock. If not in stock, record this on DA Form 2404.Clutch Drag
Inspect for clutch drag:
1.	Push in clutch pedal.
2.	Shift into first gear.
3.	Shift back to neutral.
4.	Release clutch.
NOTE: If transmission was hard to shift or vehicle moved forward, check the clutch pedal free travel. If clutch still drags, note on DA Form 2404.Smooth EngagerrRELEASE
CLUTCH
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PUSH IN CLUTCH PED£