I have a 2000 Chevy Blazer 4x4 the transmission wont shift out of 2nd gear. I still have reverse, 1st and 2nd but it wont go from 2nd to drive. the speedometer also quit working it has approx. 122,800 miles on it.

Sounds like you have lost a shaft(sungear) in the transmission. It can be repaired, but you can get a used one for less than half the cost. Repair-$1300.00+, used - around $500.00

My 1999 GMC jimmy 4DR 4WD, has the same issue, i have 1,2,R,D no od no 3 is non existant by manually placing my shifter in 3. VCC vehicle speed sensor is likely the issue the transmission gets speed data from this sensor and the transmission shifts by the speed, not pressure.4L60E E in Electronically controlled. i sujest checking wiring to the VCC on 4WD vehicles is in the tailshaft of the transfer case, on 2wd its on the tailshaft also. 2 wire sensor. FYI if it were the sunshell it would not go anywhere, and if sunshell was stuck it would not have more than one gear