John Deere 4400 Hydro Uneven Speed on Hills

[JD70LPStandard]

Used my 4400 with hydrostat transmission to mow some fairly steep hills with my flail mower. When going down the slope, I found the tractor would creep along at the desired speed, then speed up (like it was coasting or freewheeling just a bit) for a few to several feet, then slow back down to the desired speed. This happened going forward and backward. The tractor went up slopes at a uniform speed going both forward and backward. I've got a lot of seat time with larger Deere farm tractors with gear transmissions, and wasn't expecting a hydro to behave this way. Is this normal for a hydro?

 

[patchnball]

what range were you using? C range will get one in trouble on any hill. Very steep and I use A range on my 4400.