Cat 301.8 2nd speed problem

[K.Borgeest]

I have a problem with the tracks.
The fast speed do not work.
When i push down the switch on the floor and push the sticks to move forward or backwards it do not move faster and it makes a noise.
Anyone have any ideas?

I think that the four hoses to the track motor is drain,pilot pressure for break,forward, backward?
Do anyone know what the working pressure should be on the two pumps and also the pilot pressure should be?

Is it so that the fast speed solonoid valve opens and increase the hyd flow to the track motors?

 

[lantraxco]

I don't know for sure, but usually the brake release is handled internally in the motor on excavators, the smallest line is pilot to shift the two speed motors. Typically pressure will be high speed, open to tank is low.

 

[Nige]

Your 4 hoses are actually the following: -

1. 2 lines, one each for forward and reverse.
2. Travel motor case drain to tank.
3. Pilot line for 2-speed travel.

The travel motor has a 2-position swashplate. When there is no pressure in the 2-speed pilot line the swashplate defaults to the low speed position and the motor works in low speed high torque mode. When there is pilot pressure the swashplate moves over, this reduces the volume in the motor cylinders and the motor works at high speed, low torque until the pilot pressure is removed.

If you'd like a full text of the functioning of the 2-speed system and a hydraulic schematic send me a PM with your machine Serial Number and your email address.