WB losing power

[STIHL GUY]

i have a belt drive bobcat/ransomes mower. it used to be fine on hills in 1-4 gears. Recently at full throttle it will not even go up the slightest hills in first gear and it will only make up halfway up the trailer gate before coming to a stop. the only thing i can think of is replacing the belts that turn the tires but im not sure if that is the right idea. any suggestions would be appreciated
Thanks

[Restrorob]

Check/adjust/replace the trans drive belt under the engine, It's not likely both wheel belts would go out/slip at the same time.

[STIHL GUY]

ok than you for your help