Equipment mechanics,,,,, mini ex track speed

[V30crewcab]

So I have a John deere 50D, its been tracking slower on the right for awhile. it finally got to where it won't push on that side anymore, like pushing a tree, chaining up and tensioning the chain, etc. I rebuilt the center valve because it started leaking, I've rebuilt the pedal linkage box because it had alot of slop.
I Just replaced the track motor thinking it was just worn out,,,,Well its still doing it, in fact its actually worse now. I have the factory manuals, but I can't figure out what controls the pressure on the track motors. the left one is linked to bucket/swing and the right one is linked to the stick/something else. any ideas? its on a job right now, but when I get it back I might swap hoses between the pedal sides and see if its the pedal/pilot system or the pressure at the main valve stack. other than that I'm not sure where to go with it.

 

[AlxJ64]

What was the source of the replacement track motor? I had a "reman" unit for a Bobcat sent to me that was probably in worse shape than the one I was replacing. The rebuilder essentially washed a take-off in his dishwasher and then painted it and sent it to me. I sent it back once I realized the brakes weren't releasing all the way because he hadn't serviced the brake piston at all.

Thats the other question... does that machine have a brake pack in the travel motor? If so how is it released on the machine and is that line getting pressure?

 

[V30crewcab]

its a brand new track motor from precision final drives in houston. it doesn't have a separate hose for the brake. its just opened with the hydro drive pressure.

 

[YotaAtieToo]

I've noticed a lot of minis have more power and speed on one track, even basically new. Tracking long distance in a straight line they will veer to one side. I kinda figured it was a plumbing deal where one line was shorter or something and just got a bit more flow.

Sounds like you have something more than that going on though.

Have you checked the rollers and idlers? We had a dozer that was doing all kinds of weird stuff at low speeds. We all thought it was the brake on that side. John deere came out and replaced the wiring harness turns out the main idler was super smoked and causing bad drag on that side.

 

[V30crewcab]

I used to be able to chain the rear, and move it forward til the tracks spin on the trailer, then chain the front. it won't spin the right track anymore. Its definitely getting worse. doesn't want to climb hills anymore either.
the front roller is about a year old on that side.

 

[rockota]

Random thoughts based more in bourbon than experience….

Hoses all clean?
Filters clean?
Idlers good?
Adjustments needed/available on EoH?

 

[Tractor Monger]

compare case drain flow from both motors. check relief valves for trash. Is the foot pedal stroking all the way, seals good? An Infrared gun will find a bypassing seal, valve, relief, etc. is another function not shutting off and robbing flow to the travel motor? Do you have a pressure gauge?

 

[RustyC]

You are loosing pressure in the weak right side circuit. Is the right side weak in forward and reverse??
Not spinning the track at all is a pressure issue, not spinning the track fast is a flow issue.
1. The pressure could be leaking to case drain at the motor.
2. The pump on that side is worn/weak unable to make the pressure.
3. Travel relief valve or line relief is opening at a pressure lower than spec.
4. Control signal to the pump is not correct. Pilot, Load Sense, Solenoid depending on design.

You need to know the pressure in the circuit to troubleshoot.

 

[V30crewcab]

yep, weak forward and reverse. I was hoping someone could tell me which relief is for that side. theres nothing in the manual that specifically states left or right side relief. it only has one pump, but theres a flow combiner valve in the main relief block I guess i need to look at, but I would think the other functions that run off that side would we weak also. guess I need to drop in a t on either side and check pressure first.

 

[RustyC]

I'm not a JD guy but having one pump eliminates the pump being weak as an issue. I would need to understand the system and how the implements tie into the travel circuit. Do you have a hydraulic schematic?
Not an easy process but you could always swap sides withe the travel motors and see if the weakness moves with the current right side motor.

 

[V30crewcab]

 

[RustyC]

My first move would be to swap #77 and #72. Those are the reliefs for each motor circuit.
2nd move would be to measure case drain on the motors and compare.
3rd move is to inspect / reseal the swivel #10. Worn seals leak pressure from the circuit. (You may be able to hear this leakage under high pressure depending on the location)

 

[V30crewcab]

ok guess the pressure compensator is in the bottom of the valve assembly. maybe the spring is broken on the right travel?

 

[V30crewcab]

So I pulled the spring on the pressure compensator and swapped sides, and the pressure drop moved to the other side. so I ordered two new springs from JD. not cheap but they are not making them anymore. wierd thing is it still has more power on the left side with the spring swapped. 2800 on the left and 3800 on the right. I may swap the old track motor back in and see what it does.

 

[V30crewcab]

Seems to be fixed, thanks RustyC for pointing out the pressure compensation valve that I missed in the diagram. While I was at it I turned the main relief back up from 3400 to 3850, factory specs.

 

[RustyC]

Glad you got things working. It should be a hot rod now.