Help on noise id

[dsrtflcon7]

hello.
just wondering if anyone else has heard a cricket/scratching chalkboard noise coming from the bottom of the truck when in motion, almost kinda sounds like its coming from the trany? and also a hissing sound when i engage into reverse then goes away in D, P, & N.

recently changed valve cover gaskets if that helps.
any help is greatly appreciated.

 

[thor999]

I would investigate the drive shaft and transmission, hopefully it is something simple.