Not shifting?

Alright guys, so as you know, i have a 2002 with a 4.0 and a V6. My first problem started today when i went to switch out of 4X4 low back to 2wd and it would switch back, but the light for 4X4 low stayed on, on the dash. Then i notice my rpms are super high, i was in a 55mph zone, and i was at lik 4500 rpm constantly, obviously im thinking that its stuck in low? or missing a shift? side note when i drop it in 2nd or 1 on the shifter, it sounds like hell and is really like jumpy when i touch the gas. anyhelp?!?