Can you duplicate the noise without the truck moving, by power braking it? Or does the truck have to be rolling?

 

good thinking...

 

When I bought the truck I had the dealer install 2" belltech drop struts, set at 2"... and they removed the blocks and added lowering shackles set at 2". So essentially a 2/3 drop.
Back in December I dropped the truck off to just have a flip kit/hanger lift done and set the rear end at 6"... thus making it have a 2/6 drop (believe it or not it does sit level lol).
From the moment I picked it up from the dealer it has been making this noise. My first thought was pinion angle or driveshaft pushing in to the case. First I got the driveshaft cut by an 1", it needed this either way or else the yoke would be in to the case too far when I loaded the truck up with 2k lbs. After I realized that didn't fix it I removed the transmission spacer, didn't fix it. After that I ordered 4* shims in order to get the pinion closer. Still no go after all that.

I'm in agreement with you, it has to be something rotating... hence it sounding like more of a vibrating/grinding noise to me.

It physically feels more noticeable at low speeds, at high speeds you hear the noise but don't really feel it.

The truck never ONCE made this noise or anything remotely close to it prior to the flip kit... it was as quiet as can be.

Pat suggested this last night, will give it a shot after work today and see if I can recreate the noise.

 

Have to be very careful when you do this. Lift the truck off the ground and support the truck by the frame. Let the wheels hang. Start the truck and put it in gear, Let the wheels rotate. See if you can duplicate the noise and vibration without a load by varying the wheel speed by just a couple of miles per hour forward and reverse. Don't spin the wheels very fast as this can be dangerous. This is a static driveline unloaded test that changes the dynamics of the frame while loaded in a different position. Once again BE VERY CAREful. Make sure you have help while doing this.

 

I've seen other brands of headers rub after a motor mount got weak. I can't see your video at work so I can't tell anything about the noise besides what you have described. Could you give me any other descriptions of the sound, ie buzz/rattle/click and how it relates to vehicle speed and rpm? Had a friends OE muffler develop a rattle shortly after installing LTs.

 

Mines close here but dosent rattle check your motor mounts I have had them break.

 

So I'm on my way home right now going to be quick. I power brake the truck for a few seconds and couldn't create the noise. So I get on the highway in floor it and It doesn't do anything until almost 4,500 RPM's now. WTF?!?!

 

Just got to to make the noise while I was brake torquing it... ugh this is annoying

 

Videos are a little short but unfortunately if I record for to long my phone won't send them lol.

Very faint but it starts to do it around 4200-4300 RPMs, this was after brake torquing the first time.




Brake torque

 

I dont hear anything odd in those clips ???

Maybe a bit of valvetrain noise, but certainly no pipes banging. Still on AFM lifters?