http://service.mtdproducts.com/Training_Education/769-01421_SM_White ZT.pdf shop manual, thoroughly inspect transmission, drive belt, idler pulleys, all hardware with hands on, making sure everything is tight & secure before tackling transmission. Read through this manual first.
Professional Shop Manuals same as above
this may help out. Took going to the mtd dealer site, looking up your model number to get the part number of the tranny, then going to my distributor site to convert in to the hydrogear part number. Then to the hydrogear part number as a dealer, and finding the part number for the service manual
You have the 310-2200 or zt-2200 tranny ZC-DMBB-4DDC-2PPX
Here is the service manual
http://www.hydro-gear.com/Main/docs/service-repair-manuals/ezt-(zt-2100-2200).pdf
Mine is doing the same thing!,,,,When the mower is cold the left hydraulic steering works, warmed up it does not respond? Troy built zero turn. Anyone seen this before?