2003 trailblazer wont go in reverse .

Alternative

Start by checking the fluids. if its an automatic it won't shift if the ATF is low.

if you feel the handle clicking into gear (you feel it distinctly fall into place in reverse, neutral, and drive) but it wont go, it might be the electronics, or it could be a bad transmission. if this problem just happened one day with no warnings of the transmission going out, its probably the electronics. however if the handle feels like its just moving up and down without falling into place, its probably the transmission linkage. should be quick and cheap in that case

This transmission is shifted by electric solenoids which are controlled by a computer, you must get the computer scanned for fault codes first.

As you press on the gas, does the sound get louder? If so, replace your fan clutch, very common to go out.

it has to do with the clutch on the cooling fan. I have had to have mine fixed at about 50 k and it is acting up again at 87k. This tends to go away on mine as the engine heats up.

I think there is a update for the pcm for that code and for the loud cooling fan best I remember

It sounds like you broke the sun gear shell in the transmission. This is real common on 4L60E. The transmission will have to be disassembled to fix it. If this is what is wrong it will have no reverse and hold 1st till about 30 and then skip 2nd, right to 3rd. Then never shift in to 4th.

Hi, you should check if the blower plastic fan is rubbing against the fan housing ,they get lose with time and make those noises.good luck C1...

This one is easy. The clutch fan is not disengaging. Mine does the same thing after it has idled a while but then will release (wind noise stops) after getting up to speed.