question about grinding/roar noise
 

Picked up a 78 Chevy c20 automatic 350 2wd there is a grinding/roar noise coming from driver side floor board, if I put my food on the floor board under the brake pedal I can feel a vibration it feels like metal to metal grinding. It gets louder with speed anything above 40 it's extremely loud making sharp turns doest seem to effect the sound. I coasted down a hill with the Engine off and transmission in neutral the sound was still there even at very low speeds I can hear it (5 - 10) mph. also if the truck has been sitting for awhile like overnight the noise doesn't seem to start until driving for about 3 or 4 minutes.

Im new here any ideas very appreciated !
Thanks!

Re: question about grinding/roar noise
 

Welcome to the forum !
I think you should check your drive shaft for bad cross joints. It sounds like one(or more) is worn.

Re: question about grinding/roar noise
 

Welcome
If it's not the front brake squealers or dust shields I'd vote Ujoints,
sometimes they will "ping" going into R/D

Re: question about grinding/roar noise
 

Spent most the day messing with it and I believe very much so the noise is coming from the transmission. There is a little bit of play in the shifter while driving i wiggled the shifter around and pushed it in the upwards position just a hair and the noise almost completely went away let off the shifter back into its resting position the noise instantly came back. Then i pushed the shifter down a little and the noise got extremely louder. Now im real confused of what it could be something in the shifter linkage or something more serious inside the transmission

Re: question about grinding/roar noise
 

It sounds as if the trans may have a bad output shaft bearing,or input shaft bearing.
I would drain the trans,and check for metal in the pan/filter.