A couple of thing s that have been suggested that I would like to reinforce: First, be sure you are using genuine CaseIH HyTran Ultra fluid. I buy mine from my local CaseIH agricultural dealer. Second, buy and use a quality filter. I like Fleetguard, but any of the listed filters are fine.
Here is a link to help you change your HyTran and have a bit of fun doing it. It is important to have a rear cover gasket from Cub Cadet or CaseIH, not try to make something out of silicone or Form-A-Gasket.
http://www.ihcubcadet.com/IHCCFAQ/HytranChange.htm
This link talks about HyTran fluid:
http://cubfaq.com/hytran.html
All of the filters listed in this link are good:
http://cubfaq.com/HydroFilterX.html
Here is the part number for the cover plate gasket: IH-350837-R2
Good luck with your project. Please let us know how it turns out. I
hope you enjoy your 1250 as much as I enjoy mine!
Be well.
Brian Wittman