If you're gonna buy used ag equipment, you need to get yourself some EvapoRust. And PB Blaster. Lots of PB Blaster. I'd say AeroKroil, but that stuff is spendy.Over the summer I bought a used 3-point post hole digger. We're setting a bunch of fence posts and running about 600' of fence. So, let's use the auger! Nope. The slip collar on the PTO attach collar worked fine. But the ball detents weren't retracting and it was completely corroded up so I couldn't get the PTO shaft in there. I took it apart, WD-40'd the hell out of it, let it sit overnight, cleaned all the rust off, and fidgeted with the detent balls until they freed up. Cleaned it all as best as I could with a wire brush and some steel wool, put it back together and it worked like a champ.
I've never taken something like that apart and fixed it. Best part was the brownie points I scored with the wife. That and I smelled like WD-40 all day. Bonus...