Hydrostatic transmission-Suddenly forward is weak

[larryuno]

Hi, the mowing day started normally. After about half acre one of my (rear) tire chains slipped free and caught in the mower-sending me back to the shop about 1 1/2 miles away to repair it. After that I began again and mowed normally for awhile more then after moving to a steeper slope noticed the tractor slowed considerably on the uphill climb. Tractor is Husqvarna YTH18542, transmission TuffTorq K46bt. Notably, reverse is now faster than forward on the level, and has more notable torque. I checked the drive belt, and it is still like new, but sprayed belt dressing on it just in case. No improvement. I performed a transmission purge as per manual. No difference. Mower deck disengaged, no improvement. Anyone with an idea as to the cause? Does it sound like a bad transmission? It has likely less than 200 hours, when I got back to the shop the infrared thermometer read 130°F on the trans. The linkage seems tight, no obstructions, the forward throw is 1/2" to 5/8"