IMHO, running in 4x4 mode all the time is probably the issue. Worse on highway or hard surface but it still creates a lot of stress in the drivetrain whenever you turn regardless of the surface. Most MFWD front ends are not limited slip but full, locking drive. Even when turning. I know lot of people on TBN run in constant 4x4, but IMHO don't do it. It is more strain with FEL on tractor due to the weight. We have ag tractors and do not run them in constant 4x4. It is not recommended. It creates too much stress on the drive line and excessive tire wear. Our ag tractors can be switched into 4x4 but will automatically cut out when I turn the wheels about 10-15 degrees. I can switch the front end into a constant locked mode and I do that when stuck in mud or turning in mud and need the traction. Most of my field work is done in 4x4 mode but only when going straight.
On CUTS and utility tractors, just use 4x4 when you need it or think you need it:thumbsup: