Matt G. You're making me want a loader more and more.
Charlie P. That outfit is coming along great!!!
Dennis F. Somewhere (it was moved before our remodeling/addition) is a Hydro 656 torque tube. It is supposed to be part of the museum one day when we finally have the resources to assemble a true space for such a thing. If I recall Sunstrand was instrmental in developing the IH tractor hydros as they were developing the combine hydros. On page 10 of the 15U Series Service Manual under the Heat Exchanger heading it states that the hydrostatic transmission should NOT exceed 200* as a continuous operating temperature. When a hydro does get too warm and the transmission starts to slipping it is wise to shutdown as soon as possible and let the system cool down. Occassional overheating shouldn't cause excessive damage.
I know of a John Deere 318 that the PO used 90 weight oil instead of the reccomended oil. The tractor is used only about 20-25 hours a year and that 15U slips even when lukewarm. Too heavy of oil caused premature wear.
A little tip as far as my thinking goes.... When someone says that their 10 year old (or newer in some cases) hydrostatic propelled lawn or garden tractor won't go up a slight incline without slipping once the oil gets warm there is a fairly good chance that the implement relief spring is going bad. Sure you can replace that only most of the rest of the transmission isn't going to last too much longer. Those cheap box store tractors may have a decent engine only the hydros aren't built to last.
Now a little bit of when someone says to me that my 15U transmission in my Cub Cadet , JD, etc. tractor's hydro is slipping and I've heard that it will be BIG $$$ to fix. The dealer told me so. The dealer will always state worst case scenario and one must remember that a lot of them are getting $50-75.00/hour to work on your tractor. The labor alone will soon eat up ANY tractor's value. I say this.... download the manual, study it and then buy the gauges and begin troubleshooting yourself. Worst case scenario is this... Yes, you may need another hydro only you can buy a good used one pretty reasonable and install it in your newly acquired tractor and then be good to go.
One final tip.... Those implement and charge relief springs do wear out the same as the check valves. On the charge relief and implement relief area one will also want to check and see if the poppet isn't getting worn out. These are simple and inexpensive repairs.
Enough of my ramblings.... this is just some of my thoughts.
Frank C. That durn bull bucked me off way early.
Mike M. Nice little Cub Cadet. Definitely a keeper.