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Discussion Starter · #1 · (Edited)
Firstly, as will become apparent, this applies to 4x4 models only. My truck is a 2nd Gen (1994-2001). I'm not sure about the configuration of the other generations, so this may or may not apply.

The Symptoms
So, about a year ago, I was chasing an awful noise/vibration for months before I discovered what it was. It was very similar to a wheel bearing growl but was completely random. It would drive perfectly OK for a while, then it would start and would sound as if you were driving over the warning strips to the outside of the fog line. The frequency of the noise was speed dependent, not RPM dependent. When you slow down to 10-20 mph, it would turn into a clunking/rattle-clang (Sounds strange to describe it in words, but if you've heard it, you know what I mean). If you stop and start again, it will have gone away... for a while.

My experience is that it was progressive. It started only showing up at highway speed. You could slow down to 45 and it would go away. Over time, it would happen at slower and slower speeds. To be clear, this is not the death wobble, that is much more violent. It is very similar to a U-Joint or a wheel bearing growl/vibration, in that it is a constant drone, but it will go away and come back seemingly randomly.

Also note, that this noise will go away if you engage four wheel drive. As you'll see in a bit, the shift collar is stabilizing the joint in the front axle shaft and preventing it from shaking.

The Problem
So, the issue turned out to be a failed pilot bushing/bearing between the inner and outer shaft of the front axle on the passenger side. So 2nd gen Dodges don't have locking hubs like other trucks, the passenger side front axle is split with splined ends on either side of the split. A shift motor moves a splined collar across the split to engage the front axles for four wheel drive (Chilton's manual page 7-14 figure 43).



So the stock axles come with an integral polycarbonate/oil impregnated/graphite something-or-another composite bearing/bushing.



In my truck, this bearing was completely disintegrated.



This meant that the outer shaft could "wobble" around on the small shoulder. At lower speeds, two shafts would simply rub on each other. It was not until this joint got thrown slightly out of balance that it would cause the harmonic vibration.

The Fix
You cannot get this bearing without buying the entire axle shaft. As I did not see this necessary, I decided to machine a replacement out of oilite. I should stress that this is not pure brass or bronze, oilite is made by pressing fine bronze granules together under high pressure. This makes it porous to oil.

Firstly, I machined the end of the inner axle to true up the surfaces that had been beaten up.



Then I started in on the bearing.



I increased the thickness of the thickness of the thrust flange to 0.125". I finished the outer diameter to 0.001" less than the inner diameter of the outer shaft. Then I bored and reamed the internal diameter out to 0.004" larger than the diameter of the nib on the inner shaft.



Then I pressed the bearing into the outer shaft. Used a rubber mallet to set it.



Then put it back into the truck. Note, this setup requires that the housing be filled with gear oil. I've been running 90W gear oil. I have yet to have an issue with it.



If you don't have access to the machinery or the material to do it yourself, you could have a machine shop make you one, or simply buy the new axle shafts with integral bearings.

I couldn't find anyone online who has had the same problem. So I don't know it has ever been an issue before, or simply nobody posted a story about it. Hopefully, this saves someone a significant amount of diagnosing time.

To check if this is your problem, remove the cover on the axle housing. If you can move your outer shaft up and down relative to the internal shaft and/or your bearing is now a washer (as mine was), you can be pretty sure that this is the problem. If this isn't the case, look to your wheel bearings and/or u-joints.
 
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