There is a long thread on this in the "Tractors" forum under Snapper RER drive wheel. Walt Conner

I can not believe that JD dealers accept a customer's property into their possession for repair without acknowledging so with paperwork. That paperwork establishes that the dealer is in lawful possession of the property and would be necessary in the event of a catastrophe like a fire or theft. In 20 years in the motorcycle business the only time I've seen a dealer NOT issue a customer paperwork (a work order) when accepting property for warranty repair is when the dealer contemplated or actually did falsely bill the manufacturer for work not done or billed the manufacturer for a more expensive procedure than was done. This sounds way too fishy and if it were me I'd get to the bottom of this with the dealership owner or John Deere. It would be a bummer if the K58 was replaced with a K46 and I'd be real unhappy.

Oh lordy, here we go yet again. Use the forum search facility at the bottom of the forum opening page and do a search for subject like "Hydrostat oil change, Hydrostat fluid change, Hydrostat transmission slipping. This is a perennial complaint and YES, the oil can be changed (no matter what the book or the dealer say). and YES, old, degraded oil will cause symptoms like this. Many are the hydrostatic transmissions still going strong that would otherwise have gone to the scrap yard but for an oil change, which is not that hard to do (you said you are handy, or know someone who is). :^)

i think there is a spring that holds pressure upwards on wheel, but also the shifting parts must be adjusted properly. are you sure the clutch cable parts aren't binding and stopping wheel from going up? stand it up on the rear end and have someone push the clutch and watch all the parts, pretty simple once you see it in action. Only other thing i can think of is the drive plate on the engine has some how slid up,dont even know if that is possible, there is a set spec for where it sits on the shaft. If you havea "easy clutch" which is a update on those so you dont do a wheelie when you let out the clutch, that can slip if worn out even if the rubber wheel is in contact with drive plate. Others here can probably tell you more than i. I have 2 snapper RER's but havent used either in ages, nor worked on them, so i forgot a lot about them im sure.