I bought a new 6x4 diesel in '01. Good machine, rough ride. Dealer installed a shock absorber to the accellerator pedal which helped dampen the movement over rough ground. It would climb nearly any hill I wanted to go up, just had to get used to the fact that the front end would come off the ground when you topped the hill. It wasn't really good in the mud, not much ground clearance and would bottom out quickly. The '04 HPX diesel I traded it for has been a real improvement over the 6x4, better ride and handles mud much better.
It was a good, heavy duty machine. The diesel engine had a bad rompiing surge in it at idle that the dealer couldn't fix. Finally replaced the engine although it probably was the injector pump. The brakes didn't stop very well and made a lot of noise. Added a bottle of John Deere Friction modifier to the trans fluid and it cured the braking problem.
My HPX has been almost trouble-free. I hope I can trade for a new model this fall.
The brakes are inside the trans. When you change the fluid, add a pint of John Deere Friction Modifier to the trans. It made all the difference to the brakes on my 6x4. Your brakes may be worn out but it's worth a try.