Help with a mystery Chirp/squeal

I need help!
I have a squeal coming from my undercarriage SOMETIMES. I live in Houston and the squeal only shows up when its cold. Im about 75% percent sure its not belts but im no expert and could be wrong, it just doesn't sound like squeaky belts to me. Sticking my head out the window to locate the noise, my first guess would be my front-most U-Joint.
Here's what i know:
It only squeals/chirps when its cold.
It really only happens when I'm moving(usually faster than 20)
It goes away while accelerating.
Its at its worst when letting off the gas to coast.

Any ideas would be extremely helpful!

 

I too have those symptoms except it does not have to be cold outside. I suspect it is the spare tire vibrating under the truck and I intend to lower it and maybe place some padding between the tire and truck frame. I recently lubricated the leaf spring contact points and the tailgate hinge points but that didn't help. It also might be some body mount point making the noise.

But it might be the u-joint. A while back when chasing the noise I greased the u-joints but it made no difference. I would think it would have at least dampened the noise some if the u-joint was the culprit. I keep chipping away to eliminate the possibilities.

This evening I tightened up the emergency brake cable. With the wear of the brakes the cable needs adjusting to take up the slack. I am not convinced this fixes the problem but maybe I will get lucky.

 

Saturday I was under the truck. The only thing I could do to mimic the chirping sound is tap my finger nails on the drive shaft tube nearest the bumper. I had read where the u-joints and this drive shaft section need greasing so I did just that.

I pumped grease into the u-joints until they squirted out clean grease. I had to remove one bolt in the middle joint to allow connection to the zerk fitting, but I got it in there. Into the zerk fitting for the drive shaft unit I pumped 28 times before it started showing signs of being full. It must be a spline shaft in there that had become dry. I over filled it by a few more pumps, then removed the zerk fitting and bounced the rear of the truck to relieve pressure associated with over filling.

I am optimist that this will squelch the crickets and will report back at a later date.

 

Regardless of this fixing your noise, and hopefully it does, happy to see you pulled that zerk to relieve the hydraulic pressure built up after 28 pumps of grease, lol. Sometimes it's not a bad idea to just pull the 8 nuts and bolts to remove the shaft and separate it to grease the splines and ensure the grease is making it's way to where it should. If you separate the drive shaft, it has to go back together so the splines line up the exact same way they were before you separated it... Most already know, not trying to be captain obvious.

 

Thanks for the additional tips. Maybe when I get a chance I will pull it completely apart. So what happens when there is more weight in the bed than my body weight compressed and the hydraulic pressure is greater? Does it blow a seal or is there a planned escape route for the excess pressure?

 

The Toyota drivelines I've had apart have had a felt seal on the shaft that should allow the air to escape as the grease is inserted. What I've found on almost all of them though is the felt seal hardens through the years and makes it much more difficult for the air to escape creating a build up of pressure. This excess pressure can shorten the lifespan of bearings at the diffs and the t-case. I always do as you did and remove the zerk to allow the pressure to escape, if it has built up.

 

i had these exact same symptoms, it was the carrier bearing, very common issue. also check your transmission mount.

here's my detailed diagnosis.