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Drone/Vibrations on Highway 70 mph +

T

thepdk

NAXJA Forum User
Location
Detroit
Hello,
I have 98 4.0l w/ 175k miles. Stock chassis & drivetrain.

I get what I can only describe as a "drone" at highway speeds. It's not exhaust drone, almost sounds/feels like a sub woofer noise, low frequency. The dash vibrates a bit letting me know it has some kind of vibration.
It starts at around 70 and stays consistent as I increase speed. Does not vary with RPM either, as soon as I slow down it goes away.

I have replaced lots of parts and have done quite a bit of maintenance however still have it, although It is much better than when i bough it 3 months ago.

I have replaced the following w/ new components:
Wheel hubs/bearings
Both front U-joints
Front Drive shaft U-joint (all other u-joints feel tight)
Front brakes (pads/rotors)
4 Brand new firestone winterforce tires 225/75/15, 100 miles on them. Road force balanced.
Replaced both diff and TC fluid.

Anyone else suffer from this? What fixed it? The noise beats you up pretty good.

Thanks
 
Several thoughts come to mind. 1. Have a close look at rear driveshaft slip yoke where it goes into the transfer case. Grab it at the u joint yoke and attempt to force the slip yoke up, down and sideways. There should be zero play in any direction. Play here usually indicates a worn slip yoke. 2. Drop the rear driveshaft and grease the slip yoke splines excessively and reassemble and see if the noise is better or if the noise changes. 3. You could be hearing a bearing in the transfer case in the process of failing. At 175k, you might consider refreshing the transfer case anyway as a PM item, at which time all the bearings can easily be changed. 4. You could be hearing an outer rear axle bearing failing. 5. You could be hearing a rear differential carrier bearing failing. 6. You could be hearing a pinion bearing failing. 7. Your transmission mounts could be shot and you could be hearing the exhaust system hanger rub on the transmission crossmember (very common issue at this age/mileage) 8. You've thrown a balance weight off of either driveshaft. I'm sure someone else will have other items to consider.
 
sounds to me like tire/road noise. your new snow tires are more aggressive than a standard all-weather tread but quite compared to an m/s treat.
check your air pressure. air them down to around 25 or 26 and try it again. if the noise changes that's your likely culprit.
dont forget to air back up......
 
I have this same issue. I have found that my drivers side rear axle bearing has up and down play and the yoke on my 8.25 has stretched. The u-joint has some play within the yoke.

I keep it under 65....
 
I think mine is from the rear drum. The emergenecy cable broke which is the adjuster for the brakes. Mine rubbs when you turn the tire.
 
What happens when you remove the front driveshaft?

It very well could be the splines or u-joints in the front driveshaft.

My new rear driveshaft caused a hum starting around 65MPH.

Vibrations may also be worn bearings on the driveline. Both my front and rear axles had shot carrier bearings when I bought it.

So you may have more than one problem.
 
Its quiet when I took the front driveshaft out. I rebuilt it this weekend. Everything was good in it but I replaced it anyway since I had it out.
 
If the splines are worn, replacing u-joints or the centering ball won't eliminate the problem. Could also be the front output bearing(s) in the transfer case. You have to take the transfer case apart to change it.
 
Will pinion and carrier bearings make noices if the front driveshaft is out if there bad? Or will it only make noices if it is under load from the front driveshaft?
 
Thanks for the reply's

So for an update:

I swapped front wheels, still have same noise, no difference.
I also replaced the trans mount but the noise is still there.
I have the parts to replace the cardan joint but haven't yet, I'll do it this weekend along with a rebuild of the rear brakes.

As much as it pains me, I'm going to take it to a shop and let them diagnosis it.
 
Update 2:

Still have the same noise/vibration

I replaced the Double cardan joint, ball and ujoints. Also well lubed the splines.
The front shaft is now fully rebuilt. Zero play.

I also replaced the Track bar, and got an alignment. Toe was bad but made no difference.

I removed the rear drive shaft, and greased the rear output shaft from the TC. I didn't replace the rear ujoints, although they look old, they function as they should and don't exhibit any play.

All this might have made a very slight difference but still have the pulsing noise/drone/vibration.

Ive also tested the motor mounts,
Points of concern:
The rear dive shaft is pretty rusty


I feel very slight play in the rear output shaft of the transfer case. It's not from the splines, I removed the driveshaft to test.
Holding the shaft it has very slight play up and down/side-to-side. Almost not enough to see but it does make a little clank noise. This is the only "play" anywhere in the driveline. I have read multiple conflicting information on how much of any is acceptable.

help!!
 
It'll be fine.
Pull the rear shaft and do it.

Instant 50% elimination.( also may confirm my first statement of front transfer case output bearing)
 
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