Never had any engine or transmission problems with the 4420 other than had some difficulty getting the gear shifter to stay in reverse sometimes. It would tend to pop out while backing up sometimes. Had a lot of problems last year though with 2 hyd. pumps, hyd valve that controls reel height, header lift and variable speed. It had an undetectable internal crack in the valve that blowed holes in 2 hyd. pumps as presssure was leaking internally instead of letting the check valve release. Then primary countershaft, bearings and holders and a few other minor things went out. Had a chance to trade for this 88 66620 Titan II with only 1098 hours so I took the opportunity to trade up and get more capacity which I really needed. I love the 6620 but have no real complaints with the 4420 It was a good solid machine. I have heard horror stories about the 4425 and 4435 so I would steer clear of them. Been following the saga on your 4400. So how has that been progressing IJ By the way nice page showing your tractor restoration !