Hello all, first time user and first time tractor owner. I have a 70 ford model 753. 3000 I think. 3cyl 6 speed. Been loading and unloading soil all week then all of a sudden it would barely move in 1st gear when I would try to scoop up a pile. For a while I was able to put it in 2nd drive around fast for a couple seconds put it back in first and have power again to scoop up soil and drive around at proper speed. Now tractor barely moves in low gears and doesn't move in hi gears. The tractor shifts fine the engine runs great. All fluids were drained and topped off proper Could this be a problem with my transmission. Need some expert advice please. Thank you nate