Inherited 1450

Ok, I need some advice. I have inherited a Cub Cadet 1450. It was my Grandpa's tractor. This tractor was kept in excellent condition and used regularly as a mower and with a snow thrower for 20+ years. Then it was left outside with a tarp over it for 10 years. It was left in the care of my mother and step father for the past 10 years. The lever that controls the hydraulics broke and wasn't fixed. At some point, an attempt was made to fix it, but due to time and money, wasn't finished. Another cub tractor, a 1250, was bought to be used for spare parts, but it ended up sitting under tarp also.

Anyway, over this past weekend, I changed it's oil, and cleaned it's carb, and replaced the battery, and when I turned the key, it started right up. The only problem is that it won't move. I don't know much, if anything, about the hydro transmission, so I'm not sure what to do. When I push the lever forward, the tractor won't move no matter what. If I pull the lever all the way back, the tractor will creep backwards.

I have both the snow thrower and the mower deck and would love to get this tractor running again, if for nothing else, as a memento of my grandfather. Does anyone have any suggestions? Any help would be greatly appreciated.

BTW, I also have the 1250 tractor also that I believe was bought for parts before the 1450 was left to rot. If it is possible that I can use something from it, that would be great.