im having the same problem in my 99 4x4 blazer, changed the 1-2 solenoid like a month an a half ago and yesterday is stuck in second again, does it every now an again just stick for a couple days then drops out, but i noticed last night if i manually shift it then switch to drive when i get up to speed it does fine, till i have to stop anyway then i gotta start all over again.

 

If it won't shift out of 2nd, it could be the 2-3 shift solenoid.

 

well it lurches from first to second at around 20mph and it sounds like it really has to wind out to shift, an then at random times just sticks in second, wont shift any lower which is a pain cause then it takes forever to get up to twenty, but when its stuck in 2nd theres no lurch.