Your take on these noises

[07TrailyLS]

rather than making 2 separate threads I think it would be easier to ask two questions together. The first video I'm linking is my truck parked next to burger kings drive thru window this morning to amplify the noise. Ever since I bought my truck from the chevy dealer with 50,000, it's made this noise. It's hard to hear but to me it sounds like tiny pebbles in a tin can going round and round. I don't know if it's valve train, or outer engine such as the water pump, but it is intermittent and is not always there. If you turn up the volume you should be able to hear it over the idle. All I can think of every time I hear it is the timing chain. It can't be a lifter or anything like that because it does not decrease or increase on throttle. The noise is just there. It only does it while idling. Park, drive, doesn't matter. but I'll see what you all think.

The second video has a click coming from my rear axle I'm pretty sure. It's a short 5 second video showing how the rear end pops 4 during acceleration and let off several times like Rice Krispie treats hitting milk. I just put brand new acdelco u joints in and was sure the problem would be solved. Well low and behold, it's still there.

Back history would be 2007 LS. 95,000. I've changed oil and filter every 3-5 thousand with Mobil 1 full syn. Since I bought it 2 years ago. Rear axle fluid has never been changed (since I've had it at least). Trans fluid wasn't changed since I've had it, but is still a nice red and at the full line. Coolant has also never been touched. And I recently realized after using my torque app that my trucks only running at 186 degrees. Don't know how long it's been like that since that fake dial always reads exactly 210 or 1 notch below . Any more info just ask . Thanks guys
EDIT: I have taken the serpentine belt off and let the truck run for 15 minutes last year to no avail. Engine sound persisted.

 

[jeffro312]

Hey not hundred percent what it is but to rule out a couple things.

Depending how mechanically inclined you are if you can remove your serpentine belt off the truck then start the truck for a short brief time with engine warm see if noise is still there without belt.

If the noise is gone without belt on then it's something outside engine like pulley or w.e. moving parts are there.

If sound persists then inside

Just some troubleshooting tips

As far as your second question goes my I can't explain what that sound is sounds like something metal swinging under truck and when you go fast it gets enough momentum to swing hard enough to hit metal and make that noise. Haha just my thoughts. Is your spare connected under there?

I'm sure the smart guys on this forum who know a lot more then I do will chime in. Figured I'd give you something to do until then

Post your findings about engine with no serpentine belt and go from there

Edit: also as far as differential fluids I think I saw every 50k to change that

Truck I think is supposed to run 195-210. Mine is usually 197 -205 ish. You may have the lower temp thermometer. Has that ever been replaced that you know of. I have a 2004 Buick though not sure if all mad equally

 

[07TrailyLS]

Yeah. Mine rarely ever hits 190. I doubt someone put a 180* stat in before me. Just worried it's been doing it a while and my cat could be starting to clog.

 

[Mooseman]

Have you checked the level and condition of the diff fluid? You should plan on changing that as well as the transfer case fluid, which has a relatively short 50k mile interval. Don't forget the front diff.

Your t-stat is probably fine but if it was replaced with an aftermarket one (likely), it might be on the low side. I put in a Gates at first and found it to be on the cool side. Put in an ACDelco and it ran at 190. Although I haven't looked at the 4.2 TB lately, my 5.3 Saab runs at 190.