Help!!!!!!! Cant stop!!!!

Ok 2010 sportsman 550 xp
Driving me nuts. Hard to shift and brakes wont stop it. All fluids good. Just changed ADC and front diff. fluid. Pulled drive belt looks good. Primary secondary seem to be right to spec and working properly. The faster i go the better it runs and can brake. But when going slow or coming to a stop squeals like crazy and jerks and wont stop or shift. Turn key off shifts like butter. Will not start in gear even with brake engaged. Now when i hit switch for 4×4 it starts a slight squeal and if move switch to ADC bangs and jerks and vibrates like crazy.
I am lost! Need machine bad. Its been down for quite a while. Any help would be appreciated…we be poor…cant take to shop…but i can by the parts and fix if i knew what the heck was wrong????? Thanks