My 2004 chevy trailblazer won't shift from second to third gear

the t/b and envoys have known trans problems 1 is torque converter other is sun gear /basket failure --the diesel would cause rough and some performance issues but not really tranny problems have vehicle scanned for trouble codes also the 4x4 module causes headaches such as going into neutral or 4x4 on its own

A few question to see if I can help. Could you possibly post a photo of this knob in the comment section below? Is yours a manual or automatic transmission? Is there any markings on or near the knob? Is it a lever like a gear shifter or a twist/ rocker switch type?

their is no round knob on center console --coin shelf-2 cup holders-shifter -cup holder- armrest --vents--rear audio control--12v acc--2 cup holders

my 2004 chevy impala shifts hard when it warms up

sounds like a broken shift cable. (the connection between the shifter and the gearbox) common symptoms are the shifter move easier than normal.and does not move to any gears (not even park or neutral).

Have you checked transmission fluid recently. If the levels are low and/or if the dipstick smells burnt, there is a good chance your transmission is shot. Check it out & let me know; may have another idea if the fluid level checks out.

no gears indicates that the torque converter clutch servo/solenoid s faulty
probably a disconnected wire from your working with the others

The end of the shift cable has broken, there is a plastic ring at the transmission end of the cable that breaks. You will need to have it towed to the mechanic.

4th clutch hub splines are stripped off. GM didn't harden the splines until 2004 or so so the early model gradually wear to the point where they are so thin they strip off - and then, no 4th gear

Bring to tranny shop or repair shop, have it scanned for trouble codes, many electrical parts and solonoids in those trannys, possible it may just be a shift solonoid bad or needs adjustment, much cheaper than replacing tranny. good luck!