So i have a 04 rwd 5.7 qc and it started as a squeaking noise only when reversing from rear like almost brakes scratching the rotors so i checked rotors brake and cleaned and greased all up and no change in the noise then it start making the nosie in reverse and when driving slowly forward. So i jacked up the truck from the rear wheels and put it in nuetral and started spinning the wheels and i could immediately tell the noise was not coming from the brakes on either side so i got underneath and with my foot spinning the wheels and i put my ear up to the driveshaft and it is clealry coming from the driveshaft in the middle a bit towards the rear more. not from u joints or differential or transmission. it is clearly coming from the inside of the shaft. anyone know why or how this happens and what inside the shaft could be making that noise,

 

Probably a dry u-joint. The driveshaft is a hollow tube, so, sound does strange things in it.

 

just replaced the u joint this morning and noise still there so got a used driveshaft and just finished installing 5 minutes ago and bang bang no more noise. so ive seen this problem in many post and forums. and many say u joints but i recommend to lyft the truck spin the wheels and get underneath and check where noise is coming from and if its inside the shaft then its the shaft cause mine was actually bent a bit and buy the joints while you are at it no reason if replacing shaft to not spend another 20 bucks on joints as well.