I have tried to read the other issues with whining and i really hope I don't have to replace bearing in the differential but I think it is my problem. I just want to run things by you all for reassurance.

Anywhere from 15mph and up there is a constant whine that I believe if from the transmission back to the wheels. I can't figure out where it is coming from exactly. It kind of sounds like the noise your tires make while they are driving over a concrete bridge. The sound never changes but it gets louder with speed.

I have removed the fill plug on the differential and allowed the excess oil to drain out (previous owner must have filled it on a downward slope) and it looks pretty clean.

I jacked up the rear end and pushed/pulled on the tires to see what kind of play there was...I can move the tires/brake drum/axle assembly 1/16" but based on the clunking noise when you move it, it seems like it should be more than that. I eyeballed the movement by pulling the wheel away from the diff and placing a cinderblock flush with the tire at that spot. The pushed the wheel toward the diff and it looks to be 1/16"
Both sides of the truck have this same amount of slop in the rear axle.
Is this bad?

Zac

 

I had a whine when i bought my truck and it was the rear axle bearing i think, specifically the differential bearing.

 

Okay I listened a little more carefully on the ride home, and the whine really increases in sound at 48 mph. Breaking does nothing for the sound, neither does turning either direction. Coasting has no effect nor placing the tranny in neutral while at speed. The noise remains until you slow to below roughly 15 mph.

 

Bearings in the rear are going. Replace the pinion bearing and the others inside by the carrier and whatnot. If ya dont you will cause more damage then you would like

 

Jack up the rear, and turn things by hand, it should be smooth... if you feel any kind of 'grittyness', time for some new bearings. Replacing them ALL is kinda expensive, but, still cheaper than replacing the rear when one of those bearings lets go.

 

I found this in the FSM....
INSTALLATION
(1) Thoroughly clean both wheel bearings and interior
of the hub with an appropriate cleaning solvent.
(2) If a bearing and cup must be replaced, remove
the cup from the hub bore. Use a brass drift or an
appropriate removal tool to tap out the cup.
(3) Install the replacement bearing cup(s) with an
appropriate installation tool.
(4) Apply lubricant to surface area of the hub bore.
Install the inner wheel bearing in the hub. Install a
replacement bearing seal with an appropriate seal
installation tool.
(5) Inspect the bearing and seal contact surfaces
on the axle tube spindle for burrs and/or roughness.
(6) Remove all the rough contact surfaces from the
axle. Apply a coating of multi-purpose NLGI, grade 2,
EP-type lubricant to the axle.
CAUTION: Use care to prevent the inner wheel
bearing and bearing seal from contacting the axle
tube spindle threads during installation. Otherwise,
the threads, bearing, and seal could be damaged.
(7) Carefully slide the hub onto the axle. Install
the outer wheel bearing, the locktab and outer wheel
bearing locknut.
(8) Tighten the adjustment nut to 163-190 N-m
(120-140 ft. lbs.) while rotating the wheel.
(9) Loosen the adjustment nut 1/8 of-a-turn (120
degrees) to provide 0.001-inch to 0.010-inch wheel
bearing end play.

So it appears as though there should only be 0.010" MAX of side to side slop in the wheel when it is installed properly. I have much more than that. Does anyone think that I could be so lucky as to only need to replace the rear wheel bearings?????

That would be a much easier fix
Zac

 

The chrysler 9.25 rear end is a 'c-clip' axle. That is, the axles are actually held into the housing by a c-clip on the inboard end of the axle. A little bit of in/out play on the axle is normal.

 

I have the same noise coming from the rear but i have no play in the rear tires. Does that mean the diff bearing is bad still?

 

Could be any of the bearings in there. (and there are a half dozen or more to choose from...) Probably have to pull it apart, and see what's up.

 

From the FSM...

GEAR AND BEARING NOISE
GEAR NOISE
Axle gear noise can be caused by insufficient lubricant.
Incorrect backlash, tooth contact, or worn/damaged
gears can cause noise.
Gear noise usually happens at a specific speed
range. The range Is 30 to 40 mph, or above 50 mph.
The noise can also occur during a specific type of
driving condition. These conditions are acceleration,
deceleration, coast, or constant lo.ad.
When road testing, accelerate the vehicle to the
speed range where the noise is the greatest. Shift
'out-of-gear and coast through the peak-noise range.
If the noise stops or changes greatly, check for insufficient
lubricant. Incorrect ring, gear backlash, or
gear damage can cause noise changes.
I did this and the noise remained the same in neutral as it did in drive!
Differential side and pinion gears can be checked
by turning the vehicle. They usually do not cause
noise In straight-ahead driving. These gears are
loaded during vehicle turns. I f noise does occur during
vehicle turns, the side or pinion gears could be
worn or damaged. A worn pinion gear mate shaft can
also cause a snapping or a knocking noise.

BEARING NOISE
The axle shaft, differential and pinion gear bearings
can all produce noise when worn or damaged.
Bearing noise can be either a whining, or a growling
sound.
Definitely a whining sound!

Pinion gear bearings have a constant-pitch noise.
This noise changes only with vehicle speed. Pinion
bearing noise will be higher because It rotates at a
faster rate. Drive the vehicle and load the differential.
If bearing noise occurs the pinion rear bearing is
the source of the noise. If the bearing noise is heard
during a coast, front bearing is the source.
The noise happens during acceleration, also during a coast while still in Drive, and during a coast while in Neutral.
Does that mean it is the front wheel bearings or are they referring to a different set of bearings that are between the transmission and differential?

Worn, damaged differential bearings usually produce
a low pitch noise. Differential bearing noise Is
similar to pinion bearing. The pitch of differential
bearing noise Is also constant and varies only with
vehicle speed.
Axle shaft bearings produce noise and vibration
when worn or damaged. The noise generally changes
when the bearings are loaded. Road test the vehicle.
Turn the vehicle sharply to the left and to the right.
This will load the bearings and change the noise
level.
The noise never changes during a slight or sharp turn!
Where axle bearing damage is slight, the noise
Is usually not noticeable at speeds above 30 mph.
__________________________________________________ _______________

So here is where i am a little confused. If based on what i outlined above it appears to me that the front wheel bearings are the issue. On my Dakota I had a very load whining on the passenger front wheel bearing and the noise would go away during a right turn, due to the right wheel being unloaded during the turn. It just seems weird to me that both front wheel bearings would go bad at the exact same time. Well I guess if someone replaced the front brakes and didn't pack the bearings properly, then they could both go out at the same time. When I get a chance i will take apart the front brakes and see if there is bearing damage.

Thanks again for your time and assistance,
Zac