I checked my unit last night, it's max was 3170 RPM, but it struggles to get to 19MPH. I have the WSM and am going to check the pressure settings. I really don't mind the low speed most of the time, it would be nice when I'm driving on the hard surface road to be able to go closer to 25MPH.
Pete
That confirms my WSM quote of 3200 rpm.
Hoping for the OP that it's rpm problem. Easier to adjust than the hydraulics.
I've not looked at mine, but by Arthur's description adjusting rpms shouldn't be a problem. Just need an accurate way to measure.