i am thinking of upgrading from a 4420 to a 6620 what would you look for as far as things wrong with a machine. i would like to find a machine with less than 2000 hrs if possible and i really want a hydro and reverseable feeder house.
I've got an '88 model, Titan 2. I haven't had any problems with the machine except for a weak hydro, and any machine can develop that. You'll be able to tell at first glance if a machine has been well maintained or not. I think all of the T2's had the feederhouse reverser. I would think a hydro machine would be much easier to find then a gear drive machine. I'm not so sure about finding a machine with less than 2000 hours, at least not very easily.
There is a dealer in Pa. that has a lot of them on his lot. I'm sorry I can't find the name of the place right now. Maybe someone else will post it. I posted a "wanted to buy" ad on Tractorhouse. I was very specific about what I wanted, and two days later I was hooked up with the machine I have now. Mine came out of Missouri.
Have ran a 79' Turbo/Hydro 4wd 6620 for 15 years on small acreage. The 466 is a heck of an engine especially in that small of a machine. It has been a good machine, but if you get one with a reverser check and make sure it doesn't have a lot of play and movement on the shaft. We have not abused the reverser and have still had problems with it. That is really the only complaint I have with the machine after all these years. Also, when we got the machine we wondered if the 4wd would be worth the extra money..well, now I'll never own a combine without it. Good luck!
We have a 6620 that we are going to sell. It has about 3400 hours on it and has been through the shop at john deere. We picked up more acres so we bought a 9400 It has the reverser and a hydro. My wife does 98% of the farming so thats who runs it!