on my trailblazer when my trans went out u can hear it grinding u can hear the gears starting to break and your will start to putter a new trans will cost u about 1900 good luck
On ours the regulator went out and it actually overcharged the battery , (burned up the electrolyte) was putting out 15.4 volts the first sign was that we went through 2 sets of headlights in a month...
Not 100% sure about the 2004, but in the 2005 it is inside the square box just left of the engine. (air suply tube goes into the top of the engine). You need to unscrew the box to take it off.