I love the simpliciy of the 5000 compared to any Hesston or NH moco I've looked it. It just looks like MacDon makes every effort to KISS. IIRC, my machine is a 1997 model and I bought it in 2001 at a farm auction about 150 miles from home.
The reel and balanced head are belt drive. The auger is chain drive. These drives are all easily accessible under the LH cover (which I caught on a fence so it is no longer there
)
The steel on steel conditioning rollers are chain drive inside an enclosure full of grease. I've never been into this chain except to adjust tension. The drive shafts for each roller come out of this case. Mostly greaseable sealed bearings are used throughout. The U-joints on the short drive shafts are also greasable as are the splines.
The joints and shaft splines are getting quite a bit of slop in them. Replacement might be good PM after this season, but I've considered it every year for a few years and the thing just keeps going
I don't think a U-joint failure will wreck any additional parts, it will just be the downtime of it. Any auto parts store or truck driveline supply place should have readily accessible parts. Inland Truck Parts
http://www.inlandtruck.com/ has been very good for me with any kind of driveline issues I've had with farm equipment and would probably be my first stop.
I've been told the JD balanced head is the weak point on the MacDon 5000. When you think about it, the 16' single sickle is a heavy load. So far, so good. I run sythetic gear lube in the balanced head, and I try to keep guards and sections sharp. When things get a bit dull and the sickle starts hammering, that's usually when trouble starts.
The seals on the PTO pump starting leaking a couple years ago and leakage became intolerable at the end of last hay season. I took the pump off and took it to a good local hydraulic shop.
http://www.AdamsISC.com/ Cost about $250 to get new seals.