Cyclic whining noise. Please help diagnose
 

Hello all, firstly I'd like to begin by saying thank you for your time and advice in advance if you are here.

Truck: 96' 2500 auto 4x4 5.9L odo-165k , mostly stock.(gov springs, KDP)
Issue: Cyclic whining noise that presents itself above 15-20 mph. Idling or below 10mph not audible. Braking and accelerating do not effect the noise.
Troubleshooting this far:
- Checked wheel bearings for play, all wheels good, except passenger side Rear has the slightest play. (I hesitate to include this info because I really don't think this is a wheel bearing noise, though could be)
- Engine fluids all normal and at appropriate level
- P/S works
- Noise seems to come from driver side, front of vehicle, not sure if engine bay but likely
- Speed does effect the cycle of the whining, but not much at all
I suspect it is a vacuum pump or vacuum line, or the 4x4 CAD vacuum fork shifter (yes I'm a noob and don't have posilock). My next troubleshoot is to get a vacuum gauge and test the pump and lines.

I am attaching a few videos of the noise. Please forgive the wind noise (volume warning) as well as my poor camerawork. In case you guys didn't know its hard to drive safe and record :^)

1. Me driving in an empty parking lot, accelerating up to 20 then coasting, without applying brake

2. Coasting to a stop at a stop light from ~45 mph while brakes are lightly applied. Observe noise going away as truck gets down to below ~15 mph.

3. accelerating to 20mp, then coasting without applying brakes in an empty parking lot behind a strip mall, so the sound can be heard bouncing off the wall. Noise is very audible toward the end of the clip.

I kindly ask for any advice. I am an novice mechanic at best so I could use some pointers for troubleshooting methods. Thank you

It sounds "rotational", which if I had to guess, it would be driveshaft related, axle related, or brake pad related. Rotational squeakey's are usually U joints going bad.

I did check for play in all U-joints, there was no U-joint play.

But do they have adequate lubricant in them?...:confused:...Ben

The suspension components could use a greasing, and I will get that done and see if sound persists, but I don't think that's the cause. Not to doubt you.. but I will try it. Thanks

I was referring to the U-Joints...Inside them on the bearing surfaces...Some have a zerk fitting, but lots of the newer ones do not, and the lubricant wears away leaving dry bearing surfaces which can cause a squeak...[whistle]...Ben

Joint play is irrelevant. It's as Fordzilla stated, greased or not.

I had a U joint fail (china made) in my front axle. Tight as could be. No play whatsoever. Two caps were rusted to the trunion solid, and when I went to turn they squealed like a democrat screaming racism.

Brake pad sensors can cause this too.


get the truck onto 4 jackstands, off the ground.. Get someone in the truck to slowly get the wheels spinning. You'll find the "squeal source" relatively fast.

Check the boots on your inter-cooler.
Not rotational but they could be loose or cracked and blowing.
Just trying to think of things on the driver side that would/could make noise.

P

Thank you. I will grease the U joints and report back.

I will also check the inter-cooler boots. Thank you