• Thank you for visiting HeavyEquipmentForums.com! Our objective is to provide industry professionals a place to gather to exchange questions, answers and ideas. We welcome you to register using the "Register" icon at the top of the page. We'd appreciate any help you can offer in spreading the word of our new site. The more members that join, the bigger resource for all to enjoy. Thank you!

Cat 904b drive problems

87notchbk

Member
Joined
Aug 27, 2016
Messages
5
Location
CT
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?
 

lantraxco

Senior Member
Joined
Jan 1, 2009
Messages
7,704
Location
Elsewhen
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?

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.
 

87notchbk

Member
Joined
Aug 27, 2016
Messages
5
Location
CT
130

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.


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.
 

Thomas Brooks

Member
Joined
Aug 9, 2018
Messages
20
Location
Erie pa
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
 

Mark250

Senior Member
Joined
Aug 30, 2015
Messages
1,243
Location
victoria,Australia
Occupation
heavy equipment technician
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
 

Thomas Brooks

Member
Joined
Aug 9, 2018
Messages
20
Location
Erie pa
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
 

Mark250

Senior Member
Joined
Aug 30, 2015
Messages
1,243
Location
victoria,Australia
Occupation
heavy equipment technician
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
 

Thomas Brooks

Member
Joined
Aug 9, 2018
Messages
20
Location
Erie pa
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.
 

Thomas Brooks

Member
Joined
Aug 9, 2018
Messages
20
Location
Erie pa
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
 

RICk MCENTEE

New Member
Joined
Jul 22, 2020
Messages
2
Location
66936
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
 

87notchbk

Member
Joined
Aug 27, 2016
Messages
5
Location
CT
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.
 
Top