Okay, I really need help...

[Ghost2012]

I've been to three dealerships/garages and 4-5 different mechanics... NO ONE can tell me wth is going on with my 6.2L M1009

Symptoms as follows:

Slight vibration (no banging, knocking, etc) at idle in neutral, engine running.
Increased vibration in gear (dash starts making a little noise) while not moving.

I've checked the motor mounts, harmonic balancer, belts, transmission mounts, checked for contact around the engine.

However, the vibration seems to diminish when I so much as rest my foot on the pedal and up the rpms a little. I tried putting a board under the engine and lifting to no avail, but I did notice the board "twitch" every so many revs... kind of like dag-dag-dag-twitch-dag-dag-dag-twitch.

Things I've heard it could be:

Harmonic balancer.
Motor mounts.
Flex plate.
Contact of something with something.
Underwear Gnomes.
Just a clattery old 6.2L
Timing.
Torque converter.
Transmission mounts. I can post videos, pictures and sound clips and I will buy a steak dinner for the guy who finally figures this out.

Thanks in advance guys.

P.S. I really don't want to throw parts at this thing until it's fixed, please keep in mind I'm broke but can get the money to do one major job.

 

[Recovry4x4]

There is a harmonic vibration you get from the 6.2 when the idle is low. I bump all of mine up to about 850. so much to gain, nothing to lose. Bump that idle up. If you get the drone at speed look for worn out rubber engine mounts allowing the shell to contact the frame. Also, unless you can document when the balancer has been changed, change it. The 6.2 really handles slipped balancer weights poorly.

 

[Ghost2012]

Alright, I'll order a new harmonic balancer and get it installed ASAP. Where might the idle adjustment screw be located? My service manual is 120 miles away in an old box. I don't really get the drone all the way to redline, just near idle. I do occasionally get a shudder, but that's my tires being out of balance.

 

[Recovry4x4]

See the screw pointing down at a 45 degree angle? Thats it. its on the drivers side of the pump, takes a long screwdriver.