Had a new 336 inthe early 80's. For me it was a mixed bag, maybe because of how hard I worked it. At least during the early yrs, the info in the manual was incorrect for setting the timming on the needles. I think I broke about a half doz of them before the baler mechanic at the dealer informed me of the error. After setting the timming to what the mechanic said, all was OK. Knoter frame broke early in the first season. Replacement was somewhat generic as it came with a sheet of paper telling what mods needed depending upon which model baler it was going on. The big end bearing on the plunger failed on a reg basis. Always had to carry a spare or two. Went through 2-3 bearings a season. Tongue jack on the early ones were a widow maker with the loose handle. Oh on the bearing, custom for JD Had a unique bore size and only available from JD. I made a bushing so I could use a std size bearing. Bought bearings at local bearing supply company. Cost was about a thrisd of cost from JD.
When it was working, it did turn out a lot of hay fairly quickly.