1974 830 3 point problems

I'm having problems with my 3 point lift on my 1974 830. It will not raise up all the way with a load on it. I'm not sure what's going on. I have changed filter and fluid. There is a little lever in the center of the tractor in front of the seat and behind the gear shifter handles. And one to the right of the seat that is marked L, D, LD. Not sure if these are on the right setting or if I need to adjust them.