I got the same problem. My clay rich field is typical wet in spring, holding water on the surface for weeks, and has deep ruts from the previous owner and his tractor usage. Usually, when I wait for the field to properly dry, the ruts are now hard as concrete. Mowing across them with my CK4010 and rotary cutter, is hard on my tractor, even at slow speed in the 1st range, shakes me up good. What I did was:
1. With my tractor, I mowed with the ruts, instead of across the ruts. Mowing very very slowly, its incredibly slow and counter productive. But reduces shaking of the tractor.
2. Bored to death with slowly mowing ruts with a tractor, I switched to a faster and very nimble Zero Turn. Mowing time decreased and so did the shaking, because of accurate and precision placement of the zero turn wheels.
3. Attempts to remove the ruts with a box blade and then a tiller, both failed, due to concrete nature of hard clay. Only renting a Harley Power Rake for a week, removed most of the deep ruts, followed up with a 50/50 mix of top soil and river sand spread and graded over the area. All ruts are now gone. I now make all efforts to mow when the field is properly dry so not to create any new ruts.


