My brother in law just recently bought an 04 trailblazer with about 172k on it. It has the 4.2 v6 but no sure bout the trans.
He was driving down the road when his tach revved up and he noticed he had no gears. I looked at it for him. Noticed it had way too much fluid, maybe it smelled a touch toasted. But not burnt by any means. His torque converter is spinning at least from the outside. No matter what gear you put it in the engine does not load up or otherwise give any indication that it is trying to go in gear.
A quick scan showed no codes. I did verify that the TCC slip is identical to the engine rpm. Maybe broken input shaft, sprag, torque converter? Any ideas?