Diagnosing driveline whine

[rcolosi]

I have a specific noise I am encountering with my truck, and wanted to run it by you and see if anyone has any ideas, or similar experiences.
Vehicle: 2004 Ranger XLT super cab 4X4, A/T

- At exactly 40mph, what sounds like a "moaning whine" begins and continues until 45mph, and then stops
- It does it again between 60mph and 65mph
- If I tap the accelerator between these speeds I can hear the whining start up as soon as I touch the gas.
- It sounds as it is coming from the area of the transfer case, or center of the underside of the vehicle. I do not believe it is a differential issue.
- It does it at 40 and 60 mph regardless of what gear I am in.
- It is NOT the tires. I just replaced them a week ago and the noise is exactly the same. Actually it's louder since the new tires are much quieter and I can hear the whine better.
- I replaced ALL the fluids in the driveline, and they are all correct and at the correct level.
- The transmission/transfer case/4WD all work perfectly
- The TSB has been done to re-grease the slip yoke and relieve the driveline clunk
- It is not as bad if I am in 4WD.

Any ideas would be MUCH appreciated!!

Thanks,
Bob C.

 

[85_Ranger4x4]

My parents 2002 Explorer does something like that too, it does it worse with more weight in the car too. It comes and goes depending on if the engine is working or not, coasting down a hill it all but goes away, going up a hill it is there.

The dealership told them it might be the driveshaft being bent or out of true, so far they haven't put a new one in it though, you might check that out. A bigger dealership had a tool they can put on the driveshaft that will actually tell them if it is the problem.

 

[Big Jim M]

I have to tell ya I've been chaseing bout the same sound..(noise).. After months of chaseing I have found that the SOHC has a variable intake that opens and narrows to keep mixture velocity up. The factory says these things make a sound at two different opening areas. I only hear mine at coasting or slight power near 60mph..
If it's not vibrating or squeaking I'd just drive it and wait.
Big JIm

 

[85_Ranger4x4]

My parents sploder has a pretty good vibration to it too, I fogot to mention that before.

 

[rcolosi]

I have to tell ya I've been chaseing bout the same sound..(noise).. After months of chaseing I have found that the SOHC has a variable intake that opens and narrows to keep mixture velocity up. The factory says these things make a sound at two different opening areas. I only hear mine at coasting or slight power near 60mph..
If it's not vibrating or squeaking I'd just drive it and wait.
Big JIm

Thanks Jim,
Yeah.. I think that's what I'll do. It's still under extended warranty, so if the driveshaft comes flying off, I guess it's covered. And there is no vibration, so I guess that's a good thing for now!