Engine/Transmission (1998.5 - 2002) code 0720?

[GWall]

i got the code 0720 and it will not shift out of first gear unless you let off the throttle a little bit and then get back into it, then it shifts fine the rest of the gears. i changed the speed sensor on the transfer case because i looked it up before and thats what it was. it happened after i got done doing 4x4 donuts on the pavement the other day. thanks in advance.