86 S-10 stalling. WHY?

ive got an 86 s10 extended cab 4x4, 2.5 4cyl., automatic. once in a while it stalls when i put it into reverse, also if im going down the road and press the brake to hard, like if i come to a stop sign to fast. any ideas why it does this? Also when i take off the motor races up before it will shift. any ideas on why this is happening and how to fix them would be very helpfull.
thanks, Fordy8man

the stalling would be the torque converter not disengaging, the motor racing upbefore it shifts would prolly be the tranny starting to go.