641 & 651 TRACTOR-SCRAPERS Operating Techniques Caterpillar

Operating Techniques
1.1. Loading
2.1. Pusher Loading
3.1. Hauling
4.1. Dumping and Spreading


1. Reduce travel speed and downshift to 2nd; push hitch control to LOCKDOWN and check to see if ejector is to rear of bowl.

2. Open apron approximately 15 inches (0,5 m) and lower bowl to desired depth when entering cut.

3. Regulate apron opening to keep material from piling in front of lip or falling out of bowl.

4. Decrease depth of cut if engine lugs below operating range. When finishing cut, close apron, then raise bowl.

Raise and lower bowl rapidly to pump in loose material. When finishing in loose material, raise bowl slightly, close apron partially, then raise bowl.

Pusher Loading

1. Keep moving while pusher is making contact. Keep tractor-scraper in line with pusher. Cut deep as possible without stalling machines.

2. Raise bowl as soon as it is full. Allow pusher to help machine out of cut area.

Maintain smooth cut area when practical.


Pull hitch lever to engage CUSHION RIDE. Do not engage CUSHION RIDE on side slopes or in sharp turns.

Carry bowl as low as possible and still clear obstructions. Accelerate to highest practical travel speed.

When shifting back and forth between two highest gears, use the lower gear unless cycle time can be reduced in higher gear.

Reduce travel speed and downshift when approaching downgrade. Use retarder and service brakes as necessary to control speed. Keep engine RPM below 2100 and retarder temperature below 275°F (135°C).

In poor footing, engage differential lock. Reduce speed to permit lock to engage if one wheel is spinning.

To maneuver out of soft spots, apply individual tractor wheel brakes.


Watch for and obey flagmen.

Dumping and Spreading

1. Dump and spread material at highest practical travel speed, considering fill and traffic conditions. Approach fill in line with dump area. Lower bowl to desired spread height.

For better control while spreading, push hitch lever to LOCKDOWN.

2. Pull apron lever at start of dump area. Push and pull apron lever to loosen sticky material before moving ejector.

3. Pull ejector control after material has fallen from back of apron.

4. Push apron lever when bowl is empty. Pull bowl lever and raise bowl slowly to leave fill area smooth.

5. Push control to return ejector to rear. Pull hitch lever for CUSHION RIDE (if not engaged) for return to cut.