[AllanC]

One way to start the diagnostic process is to find a level, straight road with a good surface and very light traffic. Take the van up to about 60 mph, shift to neutral and shut down the engine. Be mindful that the steering will be difficult with no power assist but that should not be an issue on a straight road. As the vehicle slows note the speed when the noise is loudest. If the noise disappears when the engine is not running but vehicle is coasting, then you know it is not a driveshaft or differential or transmission noise but an engine noise.

 

[djsamuel]

It could be the start of an issue with the CV joint. If a vibration is caused by a problem in the half shaft, it's effect will increase when the rotational speed of the shaft matches a harmonic in the car. That's when it would be the most noticeable. However, the speed band you mention (45 - 25) seems a bit wide for it to be a harmonic of some sort. Could also be tire or bearing noise. Does the sound change if turning in either direction while the vehicle is making the noise?

My guess is, if it isn't having an effect other than noise (you can't feel any vibration, the car doesn't pull to one side, etc), as time goes on it will get worse. At that point, the cause hopefully will become more apparent.

 

[ImperialCrown]

I've heard a 'buzzy/reedy' type noise when a splash apron or splash shield starts vibrating in the wind. Once they start, they usually keep vibrating until the vehicle slows to a point where the road draft isn't sufficient to keep it vibrating. They won't really change pitch or volume.
Look for loose or unfastened splash aprons at the front behind the grille, at or under the radiator or at the inner fender area.

 

[MoldyOldy]

Sorry for taking so long to re-visit this, but I've been busy & out of town.....The noise started again last night, and I threw it in nuetral & killed the engine...noise still there.....Now, I'm getting an occasional low "growl" type noise, best way to explain it would be it sounds kind of like the noise you used to get with snowtires on clear dry pavement.....and a very slight vibration in the steering wheel.....I did the axle shafts @ hubs about a year and a half ago (less than 15,000 miles) so I'm wondering if maybe the parts were defective? Would I feel it in the steering if it were a differntial/transmission isue? Thanks again for any help.....

 

[Bob Lincoln]

Did you center the engine in its mounts when you replaced the axle? That's mandatory. Vibration, wear, and CV joint disintegration can result from the engine/axle combination not being centered.

 

[KOG]

Wheel bearing is a possibility.

 

[djsamuel]

Wheel bearing is a possibility.

I agree. The growling sound sure sounds like a wheel bearing. Does the sound change between a left and right turn?

 

[MoldyOldy]

Took advantage of the tiny window of opportunity we had here weather wise....Changed the front hubs, noise still there....I guess next step would be axle shafts once the weather gets a little more bearable, snow in the offing here.....

 

[MoldyOldy]

Noise is pretty much permanent now, more of a growling/grinding sound.....when I throw it in neutral and kill the engine, the noise doesn't go away....this is really getting annoying!! Hoping it's just a CV joint or something easy.....when I did the hubs though, the shafts still seemed to be solid and tight.....

 

[ImperialCrown]

Replacing the axle shafts without confirming that the noise is from them would be an expensive guess. If the noise is happening almost all the time now, that could be a good thing as it will make finding it easier.
If you can safely support the vehicle or get some lift time, I would raise the vehicle off the ground. With it running and in gear with the wheels turning, try to pinpoint the noise source.

 

[Fishpolekid]

I have heard this problem before in my 1999 Sebring convertible, the noise comes and goes. I did notice the other day that when I heard the noise and swerved left and then right it made the noise go away.


Also notice this noise is more promanent during cold winter months

 

[B10alia]

Could be tire noise, if they're cupped or something. I'd try rotating them, it's free except for the sweat equity and if the noise moves, you know the problem's with the tire.

 

[John Wood]

It could also be the differential output bearings for the axle shafts. I've had them go before. No joy.

 

[MoldyOldy]

You're not the first person I've heard mention the output bearings.....I'm guessing that's a job for the tranny shop and I'll get raked over the coals? Or is it within the realm of a good do-it-yourselfer, one of those jobes that's not neccessarily difficult, just an involved pain in the [I should have my mouth washed out with soap for using such terms]? I've been trying to find some pics of them on Google images, but can't .....

 

[Jerry Simcik]

Umm, aren't we overlooking the obvious?

It's your brake pads.

The inconsistent noise at first is caused by the pad's metal or warning tabs starting to rub against the rotor. When you apply the brakes, the force pushes the pad up against the rotor fully, which eliminates the noise temporarily. When you let off the brakes, it usually returns. It will be worse in the morning, especially if it's wet out, as there will be surface rust on the rotor. Over time, this noise will get more consistent, and much louder. It is common on older cars the that caliper slides freeze up, so while the outside pad may appear fine, the inside pad (which is harder to inspect) may be worn completely.

Check the brake pads. It's a simple check, and I bet it fixes your problem.

 

[MoldyOldy]

Checked the pads when I changed the hubs.....plenty of meat left! When the noise started, it was a high pitched almost buzzing noise.....I'm beginning to think in terms of the output bearings, as I'm starting to feel it a little in the steering wheel now.....If it is the bearings, I'd be GREATLY disappointed, as that tranny only has MAYBE 40k on it......105ish on the van, but like most overdrive trannies, the thing was replaced NUMEROUS (as in 7) times....

 

[Jerry Simcik]

Okay, if it's not the pads, did you also check the warning tabs and look for anything else that could be dragging or rubbing against the rotors?

I had this exact thing happen - though with another car - and it was the pads. This is why I suggested it.

 

[B10alia]

Have you rotated the tires?

 

[John Wood]

You're not the first person I've heard mention the output bearings.....I'm guessing that's a job for the tranny shop and I'll get raked over the coals? Or is it within the realm of a good do-it-yourselfer, one of those jobes that's not neccessarily difficult, just an involved pain in the [I should have my mouth washed out with soap for using such terms]? I've been trying to find some pics of them on Google images, but can't .....

Leakage from the tranny output shaft seals might provide additional confirmation of a possible bearing failure.
This is pretty much a job that should be done by a tranny rebuilder. It may be possible to drop the assembly out the back, by lowering the cross member, removing the dif cover, both axles and both extension housings (driver's side is an inside housing and passenger side an outside housing). Be careful when removing the extension housings because the entire ring gear assembly will fall right out onto the ground! Then with special tools, the bearings can be pulled off and new pressed on (the cones in the housings should be replaced along with the seals). The problem here is that the bearings sit on selective shims which determine the spacing to the housing cones and the ring gear lash. That is the tricky part for proper setup and any error can soon cause catastrophic failure. Most chain store shops don't take the time to check this and they just re-use the original shims in the same way they came out. You might or might not be lucky with that approach. Ideally the tranny should come out and all measurements made on the bench to get the rear end set up properly per the manual. A few special tools are required and if you have gone that far, you might as well replace the internal clutches and seals (a not too difficult job).

Check this link out for some diagrams on a newer, but similar setup: http://www.justanswer.com/dodge/63yed-dodge-caravan-sport-hello-i-finally-determined.html