I'm not sure if this is the right forum for this thread but I believe my motor mounts are going bad when I bout the truck about 5 months ago when you would crank it or cut it of there would be a small chirp sound I didn't think much of it but now it is getting worse it's like a rattle/squeak sound if that makes any since lol but it's only when I cut the engine off or on or when I bump the pedal enough for it to make the engine twist and in reverse at idle if I hold the brake you can hear it so I assume when the engine is at the exact vibration frequency it makes the noise I am assuming it is the motor mounts if anyone has any other ideas they can share it would be appreciated because I'm sure replacing motor mouts on a duramax is probably a pretty penny thanks for any input!!
Have someone watch the engine while your in the drivers seat brake depressed and apply light throttle to see if the motor moves excessively. It would torque up from the driver side. Good luck.
Look, listen before replacing the motor mounts, could be an idler pulley (very common) or belt making noise.
It's not the belt bc it had been doing it since I got it but I recently had to replace the idler pulleys and belt and it's if it was belt I assume it would do it morethen just when the motor shakes but where exactly is the idler arm? And thanks for the help!