I have to push on the brake pedal really hard to get any stopping power. The pedals are really hard, they move very little, if at all. They are all the way up, not on the floor or anything. I took the pedal assembly apart and everything moves smoothly and freely. I just took the transaxle down and apart. Everything looks great. Brake discs are evenly worn and have lots of life left. The piston and casing braking surfaces are perfect, no ripples or gouges. The oil was clean. No metal flakes anywhere. The gears are gorgeous. I will check on how free the piston is tomorrow, and take a look in the transaxle. Also if I have it in neutral I can easily lock the tires up on concrete. The machine is very weak in any other gear than first. The speeds for the loader and backhoe are slightly above nominal. The backhoe and loader seem to have plenty of power. There are 6600 hours on it.
Is there a separate hydraulic pump in the transaxle? Maybe that is not working up to snuff.
Sound like your brakes are working good. Those older Deere's worked like that. My 310D needs lots of pedal pressure to stop. When it warms up (after 2 hrs) its much better. If the pedals are up high and firm, your adjustments are good. The only other thing is you may not have the correct oil in the transmission causing more slippage than was intended. Try replacing with Deere oil or oil of the same specification designed for internal brakes.
I had cheapie tractor supply oil in there, It supposedly met all the jd specs but maybe it has to have an exact friction coefficient to work properly. I had some violent brake chatter also. They work best when really cold, like 50 or below. That would mean I need a much thicker oil.