2000 chevy blazer, tranny was shot so I replaced with another used one. Seemed to bolt up and go in ok, each gear seems to work but the shifting is all over the place. not sure what I did or didn't do. Any help is appreciated>

 

What year truck did the replacement trans come from?

 

I think it came from a chevy van of some kind, not sure of the year, but it looked the same

 

Does you speedometer work correctly with the replacement transmission?
Did the replacement trans come from a full size van or a safari/astro van?
I ask about the year of the replacement trans because there are some odd years that do not interchange with others such as 1996-1997 transmissions are different from 1998-2000 in the S10s. I cannot remember what exactly is different, but although they look the same from the outside they are internally different.
Hopefully someone will chime in that knows the internals better than me and can explain it better.

 

yes the speedo works, I think the tranny came from a smaller van like the astro