blazer trans problem

So I have a 1993 s10 blazer witht the 4.3 auto 4x4. The other day my sister was driving down the road and as soon as she merged onto the highway the truck didnt want to pull. I go to check it out and get in it rev it up and it starts moving fine then starts bucking hard. I shifted it to 4low and it seems to run fine. then i clicked it outta 4low and it took off fine i get off the exit andit acts like its in nuetral then i shifter to 4low again and start out agin and shift back out of 4low and make it home what could this be? She just had the computert changed in it last week. and hasnt really ran right since. Could they have out the wrong computer in as i was told the trans is computer controlled

Could be several things.
Is the engine running right?
Have you checked the fluid level in the transmission?
Any check engine lights on?
If a repair shop changed the computer and it has not run right I would take it back and recheck it.
What computer was changed and why was it changed and was it a new or used one?
MT

i really dont know about the work done on it I know it wouldnt run then they replaced the computer it ran then. The fluid is fine no engine lights were on but the engine did seem to be surging

i really dont know about the work done on it I know it wouldnt run then they replaced the computer it ran then. The fluid is fine no engine lights were on but the engine did seem to be surging

The engine has to be running good for the transmission to work good.

Also if the pcm was replaced it will have to match the truck and engine and needs programed for the truck.

I would work on the engine running problem.
And check out what they did on the computer replacement end.
Good luck
MT

The '93 does not need the computer to be programmed, its not vehicle specific in that regard. If it was replaced with a used unit, so long as it came from a 4.3 with matching drivetrain, it will work. As for a new refurbished ECM, all that is usually done is that the PROM gets transferred over to the new ECM and thats all there is needed, so long as the PROM was not damaged in any way. Also this is assuming though part numbers are the same and correct.

took back to shop and they said it runs fine although it hesitates and dies constantly Im going to check timing today and try to get it ready for winter

If it dies and hesitates it is not running good.
Sounds like you need to find another shop.
Good Luck