Engine/Transmission (1998.5 - 2002) What's this whirring-moaning sound ?

[RKelly]

While traveling on the highway, and most noticably while slowing down (like while heading for an exit ramp), there is a "moan" coming from my drivetrain.

I can push the clutch in, put her in neutral, and that makes no difference in the frequency of the moan. It almost sounds like mud tires on the highway (but I don't have mud tires).

There is no vibration in the steering wheel. The rear differential has planty of fluid.

I think it's coming from the mid or front of the truck.

What is it?

PS Dealer replaced front right wheel hub assembly three weeks ago.

Also, I noticed a drip of oil on the output shaft (to the rear driveshaft) of the transfer case. Doesn't look like a fast leak, but thought I'd add that.

????????

After years of owning old Ford junkers, I must say, this is a new one for me.

Any ideas appreciated.

Thanks.

Ray

 

[John Berger]

Are you sure it's not just the normal sound of the engine? Does it decline in pitch with a drop of RPM's? The sound I am thinking of is the sound in the movie Duel that the truck made when lifting off of the throttle, but not downshifting. I don't think you would get that in neutral, though. Exhaust resonation, maybe?

 

[Steve Campbell]

Could it be from the .....

Power steering pump? Have you changed the oil in it lately. They seem to make more "noise" in the winter.

 

[RKelly]

To John Berger:

Unfortunatley, It is not linked to the rpm's of the engine. The moaning sound only changes as the actual speed of the truck changes. I could shut it off (rolling down the highway), and the sound would still be there.

Steve Campbell:

I replaced the ps fluid the first winter I owned the truck, and it's been fine since. I know the sound you're talking about, and this isn't it.

I'm starting to wonder if it is a wheel bearing. I've never had a problem with one of those, so I don't know what to expect, but the dealer replacing it a few weeks ago has my curiousity up.

I just can't figure this sound???

Any other thoughts ????????

PS It only makes this moaning sound about 50% of the time, and it's usually while going from a highway speed, to a slower speed (like gradually slowing for an exit ramp).

 

[redram]

If the sound is related to highway speed and you recently had bearings serviced, see if the sound changes (goes away) by applying the brakes or by turning left or right.



This might help you identify the sound.



Also, check your center carrier bearing on the driveshaft as a similar sound might occur if the rubber has cracked and is alloowing the driveshaft to resonant.



Good luck.



(remember to check out the rear by applying only the parking brake - this will isolate the front from the rear braking system / hubs if it's a rear axle bearing)

 

[RKelly]

Redram:

I assume you're talking about a support bearing in the middle of the rear driveshaft?

My short bed doesn't have a center support bearing, although if it did, that would be the perfect match for this sound(slight vibration) that I'm hearing.

I have tried turning the wheel, and applying the brakes, and both of those things make no change to the sound.

?????????

 

[Adam]

Wheel weight?

I know it's a long shot, but it has happened to me before. The dealer replaced a seal in the rear-end of my Cherokee and while the tire was off it magically lost a wheel weight (from the inside, naturally). Took it back and they said it was the seal "breaking in". Raised the BS flag and re-scheduled for when their driveline tech returned from hunting season. As luck would have it, I caught a nail in the tire and when I replaced it with the spare, the noise and vibration were gone. Even talked the dealer into repairing and re-balancing the tire.



Just a thought...



-Adam

 

[RKelly]

Thanks Adam. I didn't think of that. I'll head out to the driveway to check that (as soon as the temperauture gets above 15 degrees, that is).

I made an appointment with the dealer on Thursday, so if I don't figure it out by Wednesday night, may God help me.

 

[RKelly]

Solved !

Ya know how I mentioned the front right wheel hub assembly had to be replaced a month ago?

Well this sound was coming from the front LEFT this time. I couldn't locate the sound to save my life, and hitting the brakes and turning the wheel made no difference in the sound. It's just that it was louder on de-acceleration.

Thank God I bought that extended warranty.

So why are these wearing so fast?

I don't plow. I take good care of her.