I have an 1993 S10 Chevy Blazer 4x4 with a 4.3 vortex, and my problem is that when I go on the road, it shifts from 1st, 2nd, 3rd,..gear before I even go 20mph.... My transmission is automatic.

a number of issues. Tcc regulator bore worn out, the infamous check ball seat it hammered badly, or/and calibration issues. I have seen all three issues on the same trans - often!

check your kick down cable attached to the carb, it may be out of adjustment and forcing the trans to stay in "passing gear"

Hi:

Your transmission has 3 shift rails...
1st - 2nd
3rd -4th
5th- Reverse

If your 3rd gear doesn't work , you have an internal transmission problem, such as a syncronizer, or similar fail... There is not much you can fix, without removeing the transmission.

i got a 1996 chev. blazer s-s10 4.3 engine 4x4.problem i got is i got 1st 2nd & overdrive & reverse but no 3rd gear what should i do

Sounds like you have a bad shift solenoid. Not sure if the Chevys are a solenoid pack, or seperate, but it will need to be replaced.

Hello;
It sounds as though your trans is going out. How is reverse? If reverse is real strong then you may just have a solenoid going out. Drop the pan and change the oil and filter if you are comfortable doing that. Inspect the pan for metal shavings and contaminents. Otherwise it would need to go to a shop for repair.
Thanks;
Rich
RPM Northwest

Have the transmission governor checked

need more info i had a 1984 chevy half ton and first, second, and third worked fine but lock up didnt work. the problem was there was no vacum at a switch under the hood on the fire wall also your shift linkage could be out of adjustment. try driving down the road and raise up a little on the shifter.

Chevy is known for using a cheap grade of wiring harnesses that corrode over time and short out. my 93 s10 blazer had a bad wire in the transmission harness resulting in only 2nd and 3rd gear and wouldnt shift by itself, i dont know if im right but something to check into.