trans problems maybe?

i have a 2001 silverado with m30 tranny,g80 rearend, 4.8 liter engine 4 by 4, when i first got truck could pull my boat out of water in drive. took boat home one day had to make hard stop some ahole pulled in front of me, since then i cant move anything up a grade except in 4 wheel drive low. truck just sets there gas all the way to floor wont move in any other gear even 4 wheel high. when it first happen there was a rubbing sound for about a month could not find what it was. one tranny shop said was spaig maybe. all gears work good on flat ground.

your posting is not very clear on whats going on .

in gear D the gas pedal to floor what is the engine doing ?

if the engine revs up with pedal to floor in D then the tranny is cooked .

if the engine does not rev up then its an engine problem or a plugged up exhaust system ..fuel filter / fuel pressures low etc,,,.

locking up the brakes should not have caused this if the vehicle was not altered from OEM design ..