Tara Boswell

I have an 03 Trailblazer that has been great it has almost 250k on it. The catalytic converter was clogged and caused an over heating issue. We replaced a cracked radiator and fan clutch X2 then discovered the cat and replaced it. Probably 3 months after the cat replavement the transmission all of a sudden had this weird back and forth shifting from 3-4 at around 50-60 miles an hour. Then 1-2 and 2-3 shifts got sluggish not slipping it's more like a flair, I've read described, like a super soft, taking forever shift. Now if I'm at 60 and hit the throttle, it will go into 4th fine and if I'm above 60ish it holds great. It shifts great 1-2-3 when cold but as it warms up it gets soft. I replaced the valve body and it seems like all the symptoms are lessened but definitely not fixed. What could be the issue? I feel like it's not getting enough pressure somewhere to make it engage. My tranny fluid was garbage, dark and full of shiny sludge 🙁 I'm just trying to help it last until I'm done with school so I can get a job and a new car. Any ideas?

bbond105

The trans has a lot of miles on it and is near the end of its life cycle. You can hook up a trans pressure gauge to it to see if you are getting a good pressure rise under throttle, somewhere around 170 psi. max on a stock trans. You can also try some type of trans fluid additive. Most of the time an additive doesn’t work but it can’t hurt to try.