having some drive issues with a cat 904b. it doesn't seem to have the power or speed it once did. It has new cat fluid and filters and is fill to the proper level. I've checked that the brakes aren't partially applied service and parking brake. I've tested the creeper valve is properly adjusted. I've tested the pressure the pump signal pressure is ok. the charge pump pressure is ok. the high pressure drive was low didn't even register on a 5800psi gauge but it has to be making some pressure because the machine still move forward and reverse. I tried swapping the test port and came up with the same results. I'm going to remove the relief valves tomorrow and inspect them. is there anything else I should check short of pulling the pump?
Is the transmission controlled with external pilot lines or has proportional valves?
No offense, but you should double check your gauge and that you are putting it on the right test port, even on a 5,800 psi gauge you should be able to see charge pressure in the loop in neutral, much higher than that to move the machine at all.
it doesn't have external pilot lines. it has a speed sensing valve. its hydrastatic.
130 none taken. Its not the gauge i tried a 1500 psi one also same thing. i know both gauges work i tried them on the charge pressure port and they worked. i tried swapping the test ports with the charge pressure one and still didn't get anything. the only other test port in that area is for the pump case its a different fitting. seeing that it moves i know its getting some pressure. i won't have time to mess with it tonight.
I realize this is an old thread but did you ever figure it out? Our cat 904b is acting the same and was hoping to get an idea or two before I went digging into it. I don't easily have access to gauges by the way. Thank you
first I assume a BAL prefix for your machine check that the cables going from the brake pedal to the transmission are free and releasing properly Also check that the creeper control cable if fitted is free and returning also
My machine is a BKB prefix. CAT0904BKB4L00568 I did just unhook the park brake cable that seemed to be holding up on the brake also. It does seem better. I'll have to run it more than just a loop in the yard still though. I do have another issue that's been there since I bought the machine. When you turn the machine to the right, the engine and transmission bog down quite a bit. It'll run out of steam and slow you right down with a pusher of snow, so that you have to back up and hit the pile harder to move it again. Turning to the left doesn't effect the motor/ drive. Is this how it's supposed to be because of steering tied in with the hydrostatics? Thanks, Thomas
the serial number IS B4L00568 the serial number is the last eight digits of the PIN number Does the machine have the optional creeper control if you turn the machine from full left lock too full right lock and vice versa with machine stationary does it stall the engine then or only when moving Mark
It does have the optional creeper control. The lever itself is in full speed position. I haven't looked underneath yet or followed the cable to see what's going on in that end. I will look tomorrow. I'm pretty sure it does stall the machine once you real full lock stationary. I can double check that as well tomorrow.
It does stall out when full locked left or right. I don't see any issue with the creeper control. It does seem to drive much better with the park brake disconnected now but the power loss issue when turning (especially right) is still defiantly there. It has been there since before I noticed this drive issue from the park brake though
did you find your problem with your 904b? i have the same problem with mine. it is acting like hydrolic are not flowing or the brakes are on but i checked the brake controls they are ok.turn left ok turn right boogs the machine
it was an issue with the throttle linkage being rusted/ frozen. was only getting about half throttle checked the rpm. machine was used for snow removal mostly. got everything moving worked like it should.