I have a 1999 Chevy Blazer with 56,000 miles on it. It just got a major face lift. I gave it a tune up, new throttle sensor, radiator drained, fuel system cleaned, intake gasket, the whole nine yards. But after all that, for some reason, the shifitng is rough, especially at 40-45 mph. It seems fine at around 25-30 though. What could be the issue. It wouldn't be bad if it wasn't so noticable; you can really feel it.

I heard from a couple of people that it could be the timing chain, is this a possibility?

 

You seem to indicate that after the work you did it started to do this ?

 

Ever since I bought it used, the shifting was always bad. I thought that maybe after it was worked on, it would go away, but it never did. Would could be the cause.