Help diagnosing the problem

UPDATE: I installed an anti-theft cage for my catalytic converter (photo in my album). Although I initially checked it for rubbing on the driveshaft, after I crawled underneath I found to be rubbing on the shaft that connects to the transfer case. Bent it back and voila. Thanks everyone for your pointers, I did end up greasing my u joints as well.

Hey guys, I need some help diagnosing the sound coming from my 2016 DCSB TRD OR before it drives me nuts.

It developed a squeak that only is audible when the accelerator is pressed and the vehicle is in motion, so when I put it in neutral and rev it I don't hear it.

It won't sound if I am in drive and idling forward, but when I press the gas it starts when I start going around 5 miles an hour. It will get faster and faster the faster I go up until around 35 mph.

It's a high pitch sound, reminds me of the sound the brakes make when the pads wear down to the needle, but since it only happens when the accelerator is pressed I didn't think it was the brakes.

 

Driveshaft u-joints?
Original owner?
Ever been lubed?

 

If you very lightly touch the brakes while moving does it change or go away? if you brake harder does it change or go away? how about reverse? turning?

 

3rd owner, had the truck for a little over a month. Went off roading recently and it got in plenty of mud and water especially. I'm leaning towards U joint, will get a grease gun tomorrow and try it.

 

I tried braking hard and it didn't do anything. Reverse in idle it doesn't do it but I didn't try giving it gas in reverse.

Lightly touching the brakes: It doesn't do it unless I am accelerating so to answer your question no I haven't noticed that changes anything.

 

If it’s 4wd, put it in 2wd and jack up the rear diff and put blocks under the front tires and put the truck in neutral. When it’s safe, go underneath and check the drive shaft for any kind on play radially or in and out.

 

I like the jackstand suggestion. IMO if the sound increases when the gas pedal is compressed it seems to me it would be a rotating assembly. I would do the jack stand check and it would be smart to check all zerks/grease and all axle fluids.

When i have an issue I only change/do 1 potential fix at a time. This way I can learn what the cause was and any future issues later.