Drivetrain Whine

[Herkdriver]

I have an 03 4wd with 180K that's developed a higher pitch whine sound. I can't really tell where its coming from but I do know that the whine increases with car speed and not RPM. The sound appears at low speeds and increases in pitch and only "goes away" when the engine noise drowns it out. I flushed my tranny with amsoil about 80K ago and my transfer & diffs about 12K ago. My front wheel bearings and cv axles were replaced last year. I've searched around but most people who report a whine noise seem to connect it to engine RPM which is not my case. Any ideas on where to trouble shoot from here?

 

[alia176]

Can you find an empty road, run it up to 40mph or so, throw her in Neutral and shut off the ign. Be sure to bring the key back to IGN just so you have steering wheel control. Does the noise appear to slow down as the vehicle slows down? If so, sounds like something in the drivetrain, possibly the Tcase or either of the diffs.

Usually a wheel bearing may groan vs whine, for lack of a better word.

Another idea is to jack up the vehicle on jack stands, then start and run the vehicle in D. Step outside and listen for the sounds or have someone else stay in the vehicle while you try to track down the noise from the outside of the vehicle.

 

[Herkdriver]

I know when I let off on the gas the whine doesn't change until the car starts slowing down at which point the pitch begins to decrease like its winding down. I'll give your road test a shot tomorrow and see if it confirms this or if I notice anything different.

 

[mfaile]

Same issue

03 with 180k miles. Thought the sound was rear wheel bearings. Replaced them and still there. Ended up having to replace differential. Quiet as a mouse now.

 

[Herkdriver]

Yeah that's why I hate throwing parts at it when you just never know if it's the issue or not. I've ordered a set of ChassisEARs to help pinpoint the source but of course now the whine has been almost nonexistent the past few days. I'm sure it'll return soon enough and hopefully I find it's just a wheel bearing and not a diff...

 

[Herkdriver]

I finally got to test out the ChassisEARs that I ordered. Man those things are a great tool! I was able to narrow the whine I was hearing down to the transfer case and most likely the rear end of the case. I checked the fluid level and it was about three ounces low but I didn't notice any leaks and I didn't hear any difference in the noise after I topped off the oil.

Before I settle on the tcase I just want to make sure I'm not overlooking the driveshaft. Is it possible for the front U joint to make a higher pitch whine sound? I haven't heard anyone describe a drive shaft making such a noise but, as I said, I don't want to potentially overlook it.

 

[AuSeeker]

I finally got to test out the ChassisEARs that I ordered. Man those things are a great tool! I was able to narrow the whine I was hearing down to the transfer case and most likely the rear end of the case. I checked the fluid level and it was about three ounces low but I didn't notice any leaks and I didn't hear any difference in the noise after I topped off the oil.

Before I settle on the tcase I just want to make sure I'm not overlooking the driveshaft. Is it possible for the front U joint to make a higher pitch whine sound? I haven't heard anyone describe a drive shaft making such a noise but, as I said, I don't want to potentially overlook it.

It's relatively inexpensive to replace the u-joints on the driveshaft, so I would do that first and you will know that they're good for many years/miles to come and if the whine is still present you can progress to the expensive transfer case repair!