first off, Merry Christmas to everyone I noticed while plowing snow that my 580 will surge while reversing. It does it worse when reversing up a hill, I thought at first it was the boom thumping against the boom lock but it seems to be in the drive system.
Merry Christmas to you too! My 580C surged while in reverse when I first got it home and I was quite concerned about it until I figured out what I was doing. Mine has the clutch cut out control switch on the dash. The switch was in "Neutral" where if the brake is depressed then the transmission goes into neutral until the brake is released. I was backing up with my foot slightly resting on the brake so when the machine moved backwards, my body weight shifted forward just enough to actuate the brake switch, then when it went into neutral, my body weight shifted back off and the machine went back into reverse. This would cycle back and forth a few times neutral, reverse, neutral, reverse... until I realized what was going on. I'm not sure what is going on with yours, but that is what happened to me. Also I know in a car if the trans fluid is low it will sometimes go into neutral around corners, then back into drive due to the fluid sloshing around.
If you have the early 580K with the external emergency brake on the front of the diff, have seen the rotating disc worn on the splines so that it was wobbling and rubbing against the pads every rotation. That would seem logical when you notice it just backing up a hill. If you think that the rotating disc is loose on the splines and this could be the cause, let me know and I will tell you what I did with mine.
Thanks for the replies guys ,its a late model K (phase 3) machine that's kinda what it feels like, if I was to tap the auto neutral switch on either the shifter or loader control lever, I'll check into it (if and when it warms up -27C this AM) it seems to do it when under load reversing, not so much on level ground??
With that temp, I wonder if you have a fuel problem? Ice in the tank? :beatsme Engine mounts could be suspect as well???