621B TRACTOR-SCRAPER Moving The Tractor-Scraper Caterpillar

Moving The Tractor-Scraper
1.1. Parking/Emergency Brake System
2.1. Emergency Stops
3.1. Changing Gear Speed and Direction

------ WARNING! ------

Do not move machine without normal air pressure (low air pressure light must be off).

1. Be sure seat belt is fastened.

2. Move lever to EMERGENCY position for at least 3 seconds before moving lever to RELEASE. (See page 26 for additional information.)

3. Depress brake pedal. Pull lever to raise bowl.

------ WARNING! ------

Check to be sure area is clear of personnel and obstructions.


NOTE: It is possible to start the engine when the transmission selector lever is in other than NEUTRAL, but the machine will not move. Should this happen, move the selector lever to NEUTRAL, then to the desired speed range.

4. Push and turn transmission safety lock to OFF. Pull transmission control lever to desired speed.

5. Release brake pedal. Depress accelerator pedal.

Parking/Emergency Brake System

1. If parking brake does not release, move lever to EMERGENCY position. Push governor override button to raise air pressure to 150 PSI (10,5 kg/cm2).

2. Release override button and move lever to RELEASE.

Emergency Stops

If low air pressure warning light comes on, or emergency warning horn sounds, stop the machine immediately.

To stop machine if the service brakes do not; push emergency brake lever to EMERGENCY position.

------ WARNING! ------

Brakes will automatically apply if air pressure drops below safe operating pressure.

If the tractor-scraper is stopped on a steep grade by the emergency system, do not release brakes.

After an emergency stop, wait until air pressure gauge registers NORMAL before moving the tractor-scraper. If air pressure gauge will not register NORMAL, have air system checked.


NOTE: In an emergency the tractor-scraper can be moved in first gear with the emergency brake applied. Check condition of brakes before operating machine again.

Changing Gear Speed and Direction

Machine must be stopped and engine at low idle before pushing transmission control lever into REVERSE.

First, second and reverse speeds are converter drive, and are selected manually.

Select highest usable speed. Transmission will automatically upshift or downshift between second and the selected speed during operation.


Never downshift with engine speed above 1700 RPM. Downshift only one speed at a time.

Depress Transmission Hold pedal to keep transmission from upshifting. Pedal may be used when entering a curve, approaching a grade, during loading or while spreading.

------ WARNING! ------

Improper downshifting can cause sudden reduction in travel speed.

Use hydraulic retarders and/or service brakes to reduce speed before entering sharp turns, fill areas and downgrades.

Do not move transmission control level with transmission HOLD applied.

Never coast downgrade. Keep transmission engaged.