Hydraulics issues JD 440c

Log-it-up · January 29, 2019, 12:30:09 PM

Hello friends
I have a JD 440c skidder I have lost hydraulics power, I had a mechanic test the pumps and said they where putting out adequate pump pressures ( no stereing and blade function).
Here is the kicker if i wait for it to set over night it will act fine for a period of time (15 minutes or so), I have been told it may be the pick up tube for the charge pump.
I am not much a wrench guy but can hold my own i was wondering How i get to pick up tube
FYI its a late 70's 440c with a manual transmission
Thanks for your help

mike_belben · January 29, 2019, 02:29:56 PM

That gripe is consistent with a clogging sump screen. Heavy sediment or maybe even a forgotten glove or rag falls off the screen overnight and is drawn up again promptly the next day. Whiny pump cavitation when its acting up is further confirmation of a fluid starvation to the input side of the pump. That machine may not even have one, i dunno, but in general terms look at suction side for clogging and/or major air leaking in.

mike_belben · January 29, 2019, 02:33:17 PM

Further suggestion rather. Confirmation is when you fish a dixie cup out. ;D

Southside · January 29, 2019, 06:42:33 PM

Another area to check is the priority valve. I had a 540 from the same period and the valve began to stick which would cause the same issues. Basically this valve has a shuttle piston inside of it and it diverts fluid to the steering and brakes over the blade, however when the shuttle gets stuck in the middle of the ports everything stops.

Mine was on the engine side of the firewall by my right knee, multiple lines coming into it. I adjusted it per the JD specs, replaced O rings, cleaned it, nothing helped, seems it just gets worn out of tolerance enough over the years and shifts so it jams. Ended up gutting it out and voilla, problems solved.

backwoodsdave · January 29, 2019, 10:32:02 PM

Had a Ford backhoe do that with the trans, it had some watery mud in the bottom where the pickup screen was , had to flush it out good and clean the screen, also i don't know if the 440 has a rubber hose on the suction side of that pump it could be collapsing or coming apart inside and starving the pump until it sets a while.

tacks Y · January 30, 2019, 08:15:43 AM

I have a C also, I do not think there is a port to access the screen. The 440, and 440A had one, a better set up. I think you have to remove the rear cover on tranny to access. Mine is in my garage as I am putting chains on it so I will look.

mike_belben · January 30, 2019, 08:57:34 AM

If its a sump supply issue youll likely have atleast reduced performance with all functions once misbehaving begins. If all but blade and steer are normal and those two are both unique to a priority flow control then SSL is probably right. Id start there first if the strainer is an access nightmare.

If the priority valve has similar sized hoses you could swap them and look for the problem to shift, or plug the primary outlet which would give full flow to the secondary outlet. Think of an elevator shaft sitting ontop a water main. All the water travels horizontal, only excess water that reaches the third floor is going to the secondary circuit. If flow drops off, the level falls below the threshold and no flow goes to the secondary for a little while until volume resumes. Theyre simple poppet and spring valves that could probably be fixed up if disassembly is possible. They may also have an acorn nut and a preset spring seat to adjust. Try backing it off if there is one.

Brian w · January 30, 2019, 01:30:04 PM

I have a 640C I have been having similar problems with it. Mine is a power shift if yours is similar then the access to the screen on mine is on Left side of transmission behind the transmission filter there's a flat plate with 4 half inch bolts the plate is about 4 inches across. Remove the plate and then pull the screen out but be careful you will lose about 5 or 6 gallon of fluid.

Log-it-up · January 30, 2019, 09:05:12 PM

Thanks for the information guys im going to look into those things soon we got a bit of a cold snap coming in there calling for -35f so I'm going to wait for the warm up this weekend you informed

tacks Y · January 31, 2019, 07:49:37 AM

Is this power shift or 6 speed manual? My manual C does not have access to the pickup. I think there is a drain below it, pull plug drain oil and see whats in there? There is a filter on left side also.