750c series 2 tracking issues

[Trey1]

i have a 2000 750c series 2 dozer with around 5k hours. Machine was operating fine, had been pushing some trees and rock, when I finished the job I had headed to the truck. That's when the right side of the dozer started jumping sideways. Ive since then changed the fluid, filters and right side speed sensor. Will operate fine as long as you don't pull the fuel back over half way and keep the speed under 2.5. Also doesn't do it on a hillside in reverse. What could this be? Started mis tracking after this, has also thrown a f617 code a time or two. Have someone trying to tell me it's a pump but it's hard for me to believe, was operating and pushing too good to just suddenly stop, also wouldn't think the pump would cause it to be sporadic and jump all over the place. Any help would be greatly appreciated. Thanks!

 

[mikebramel]

Check the charge pressure and do you need to calibrate the sensor

 

[mrappels]

Hey there trey,
I'm no expert on JD, but from what i just read about it, the track motors are driven by individual hydraulic motors and pumps.

I would also like to suggest, if the charge pressure checks out, if the control system is electro-hydraulic, swapping the the plugs to the solenoids that control oil flow for forward movement to the motors - could always do the same with pilot lines..

see if the issue migrates from left to right. be careful to make sure that the return oil has a way out. may need to swap those too.
could be lucky and be as simple as a loose plug or broken wire..

it is also possible that there's an issue with the pump swash angle when it tries to push the oil for forward movement.. either via the fore-mentioned charge pressure, or by something more mechanical...

also, when you say it works on a hillside, are you saying that you're reversing down with the gradient? could be free-wheeling if it is the pump?

lastly, was there any temp difference between the two motors? could be a brake engaging intermittently? again, wires and pressure..

cat have a real handy doc that gives a brief on every code they use. is my bible when identifying a code on the fly.
anyone know if JD do the same??

Good Luck and hope this helps.

 

[Trey1]

Thanks you both for the reply, I've got it at a shop right now and supposedly all the charge pressures check out other than the right side pump. The problem started all at once which makes it hard for me to believe it's a mechanical problem. As far as on a hill I was meaning backing up a steep hill I could crank the speed all the way up and it doesn't affect it on a hill until you level out. From what I've seen i believe the 617 code is a low voltage code for that side