446B Backhoe Loader Transmission (Autoshift) Visual Inspection Caterpillar

Visual Inspection

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

Personal injury or death can result from escaping fluid under pressure.

Escaping fluid under pressure, even a very small pin-hole size leak, can penetrate body tissue and cause serious injury and possible death. If fluid is injected into your skin, it must be treated by a doctor familiar with this type of injury.

Always use a board or cardboard when checking for a leak.



Care must be taken to ensure that fluids are contained during performance of inspection, maintenance, testing, adjusting and repair of the product. Be prepared to collect the fluid with suitable containers before opening any compartment or disassembling any component containing fluids.

Refer to Special Publication, NENG2500, "AVSpare Tools and Shop Products Guide" for tools and supplies suitable to collect and contain fluids on AVSpare products.

Dispose of all fluids according to local regulations and mandates.

Start the machine. Run the machine until the fluids reach normal operating temperature. Lower the work tools to the ground. Lower the stabilizers. Engage the parking brake. Stop the engine. Shift the speed/direction control lever to the NEUTRAL position.

During the visual check, use a magnet in order to separate ferrous material from nonferrous particles.

  1. Check the oil level in the transmission. Look for air (bubbles) or water on the dipstick. Many problems in the transmission are caused by low oil level or air in the oil. Add oil to the transmission if oil is needed.

    1. Air (bubbles) is usually caused by a loose tube or a damaged casting that allows air to enter the suction side of the system. The air leak will allow oil to leak.

  1. Check all oil lines, hoses and connections for leaks and damage. Look for oil on the ground under the machine.

  1. Move the speed/direction control lever to the REVERSE and FORWARD positions. Also, move the speed/direction control lever through all SPEED positions. The detents must be felt in each speed position. The actuation of the speed/direction control lever must give the same positive activation to the hydraulic control circuit for clutch engagement in both directions.

    Illustration 1g00849528

    (1) Gate valve

  1. Drain the oil from the transmission case by locating the gate valve, opening the gate valve (1) and draining the oil into a suitable container. Remove the cover plate from the lower right side of the transmission for further draining of any remaining oil. Remove the suction screen and inspect the suction screen. Close the gate valve for the hydraulic oil tank drain prior to replacing the oil. Also, inspect the bottom of the transmission case for debris. Remove the transmission oil filter and inspect the transmission oil filter for foreign material.

    1. Rubber particles indicate seal failure or hose failure.

    1. Shiny steel particles indicate mechanical failure or gear wear of the transmission or pump.

    1. A heavy accumulation of black fiber material indicate worn clutch discs.

    1. Aluminum particles indicate a failure of a clutch piston or torque converter.

    1. Iron or steel chips indicate broken components in the transmission.

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