I am using the backhoe right now as a snow plow (in low gear) as Maine gets a lot of snow right now and I noticed that when I just drive the machine there is a distinct slow-surge pattern. It happens at about a 1 second interval. The machine speeds up a bit and the next second it slow. It does not stall, it does everything it is supposed to do, but it does have this funny feature, even (or possibly even more so) after it has been driven and warmed up. The engine speed does not vary, the driving speed varies. I did check the transmission oil level, but that seems fine. What could cause this?
Is your surge when crawling very slowly. If so my kioti tractor did that. I think its a hydrostatic thing. Your 110 is hydrostatic right? I believe (not an expert here) a hydrostatic drive is turned by multiple short stroke pistons pushing on a circular disc. If your working the tractor really slow you can feel each piston do a stroke. Anyway, my Kioti did this. It was more noticeable under load.
I think you are right about the nature of my transmission (hydrostatic), but I also think that I noticed the surges most when going quite fast (well at least fast in the lowest gear!). I will check the fast and under load theory next time I use the machine.
I used the machine this afternoon and the leapfrogging (surge slow surge) seems to start after the machine warms up and at any speed. I changed to a higher gear, no change. Again it is clearly in the transmission since the engine rpm don't change.
Sounds like you should be speaking to your JD technician.
gonna assume your fuel filter is clean? had a similar problem recently on a newly acquired machine...felt it one afternoon...the next morning, the problem became evident, the fuel filter was full of crud...