Kubota L4610 with Glide shit transmission. about 1300hrs. Using the tractor on the side of several hills. I've noticed several times when i have a bush hog or disk attached in the back and the bucket on the front, when i go to turn with the rear lift all the way up, the steering gets tight for a few seconds. Problem goes away if i lower the the rear lift down some. I change the fluids around 1000 hrs. no leaks, Seems to be full. Any ideas on what is causing this?