Im getting a sound like a dry needle bearing when I accelerate in 4th and decelerate in 5th. I also have a whirring sound in all gears and neutral. Mostly I am concerned about the hard to describe one. It is a sound I have heard before on old manual transmission vehicles, like a fast rattle, it could be confused with engine pinging.
I am nearly certain it is from the gearbox because it is affected by which gear the truck is in? What do 4th and 5th gear have in common that 1,2 &3rd do not?