So I just had a fluid change and a code reader done on my blazer to see why my truck doesnt always down shift. In the winter it works fine, now that its getting warmer, accelerating it goes through the gears fine, come to a stop, try to go again, it goes but it didnt seem to down shift, manually put it into first or second and then shift it into Drive or over drive after once the revs start to get high, and it goes fine. Just seems to be inconsistant.

Anyone have any ideas on what would be causing it. There are no codes being thrown from it.

 

Could either be a problem with the 3-2 shift solenoid or there is a problem with the 1-2 valve (spring broke or valve stuck) which is located behind the 1-2 shift solenoid.

This exploded view will show you where the applicable solenoids are located.

 

Forgive my noobness.

How would one go about replacing these? I have to drop the tranny dont I?

Oh and Ive been doing some searching since reading your reply, and noticed a lot of people got error codes from the tranny. Is it odd that I didnt get any but am still having these problems?