What's wrong with my jeep

I have a 2006 jeep grand Cherokee limited and it will
only move if it's in 4wd low and then it won't go over 35
or so and it says 4th gear on the dash. When I put it in
regular drive it won't go at all when o put it in gear. You
can hear the motor changing sounds when I shift
gears. I've changed the fluid in tranny and filter and
changed the shift motor for the transfer case. I don't
have much money and it's our only vehicle. If I don't fix
it soon and for cheap we will be hurting.