Growl like noise at about 30 mph?

By "new hubs", are you referring to the brake rotors or the wheel bearings? A humming noise, like an airplane engine, is caused by the wheel bearings. With older pressed-in bearings, you could tell which one was noisy by the way the noise changed when turning slightly, as in when changing lanes. Your truck uses a bolt-on assembly. Those can transmit the noise, so while it might sound like the noise is coming from one side, it's actually the bearing on the other side that's noisy.

You didn't say if this a four-wheel-drive or 2wd. With 4wd models, with the truck on a hoist, I run it, in gear, then listen next to each bearing with a stethoscope. One side will be obviously louder than the other side. Another way to find this is to raise the front tires off the ground, reach over the top of a tire, then lightly wrap your fingertips around part of the coil spring. Rotate that wheel by hand. If that's the noisy bearing, you'll feel the vibration. This doesn't work when the truck has torsion bars.

If the noise is coming from a bearing that was recently replaced, the common cause of that is improper installation procedures. Specifically, there must never be any vehicle weight on the bearing unless the axle nut is fully tightened to specs with a click-type torque wrench. Some specifications are rather low, but most vehicles call for in the area of 180 foot-pounds. A lot of competent do-it-yourselfers set the tire on the ground to hold the axle from spinning so they can tighten the nut. By that time the damage has been done. A better way is to stick a screwdriver or punch through one of the cooling slots in the rotor to hold the axle while the nut is tightened.

Let me know what you find.

This has to be caused by something that is rotating, so right there, that leaves out a lot of parts. The common noise from an exhaust leak up near the engine or exhaust manifold is a ticking noise loud enough to be heard from inside. That usually only occurs during acceleration. Running the engine, in gear, on a hoist, is no longer a thought because we do that to run the front wheels. Being a 2wd, you'll have to use the coil spring method I described. Also, improper installation procedures isn't the likely cause if the new bearings lasted two years.

For that bearing noise, turning slightly to identify the side that's noisy worked with the older-style pressed-in bearings found on older models from the 1980s. This was common on the Dodge Omnis and Plymouth Horizons. With that style, if you move from the right lane to the left lane, for example, some of the car's weight shifted momentarily onto the right wheel and bearing, making the whining sound louder. Turning the other way made the sound quieter, often going away completely for a few seconds. Those were easy to determine which was the noisy one, which was important because the bearing had to be destroyed to remove it.

With your bolt-on style of bearing, every professional has been fooled at least once, thinking the noisy bearing was on one side, then it turned out to be the other one that was bad. The noise transmits through the vehicle to sound like it's coming from the other side. The good news here is if you replace the wrong bearing, you can put the old one on the other side. Being a bolt-on assembly, they don't have to be destroyed to remove them.

This also doesn't have anything to do with play in the bearing. That only develops long after a noisy bearing has been ignored. I've only seen that once on a Dodge Shadow when the owner refused to believe it was bad and drove on it like that for years.

The 2wd Dakota uses front coil springs, so you can do the test I described by feeling for the vibration with your fingertips.

You can do one tire at a time. The vibration is subtle and would otherwise be overlooked unless you know what you're looking for. Chances are only one is noisy, so once you feel the quiet one, the noisy one will be evident.

There's also a tool for finding the causes of noises, but even a lot of professionals have never seen or heard of it. It's called the "Chassis Ear". I found the original model on eBay a few years ago for half of what the guys with the tool trucks charge. It has six wired microphones that you clip to suspect parts. Run the wires inside to a switch box with headphones. As you drive, you switch between the microphones to find the loudest one. Or, you stop and move the microphones around as necessary. You have to be careful to route the wires so nothing will catch on them while driving. There's at least one other model that uses four wireless microphones, and I think there's a model that uses all six wireless microphones.

I used a Chassis Ear once to find a noisy bearing. The tool was a standard-issue tool from Chrysler to their dealerships. After that, for me, having a hoist, it was faster to just listen next to each one with a stethoscope. These were almost all on fwd cars so I could run the front wheels in the air.

Forget about the struts. As I mentioned previously, this has to be caused by something that is rotating. Brake rotors don't make a humming sound. They can make a rumbling sound if they're badly rusted on the back side, but that will get much worse, or at least change when the brakes are applied.

When the tie rod ends were replaced, the truck had to be aligned. "Toe" is the last of the three main angles to be adjusted. If that is not correct, it will cause a choppy pattern to develop on both front tires. That pattern can set up a vibration or buzzing sound. That pattern could have developed before you replaced the parts. To identify that, rotate the rear tires to the front as long as those don't have any previous misalignment wear.

When it comes to washing brake parts, Brake Parts Cleaner is the only acceptable product because it evaporates quickly enough to not soak into the porous linings, yet it gives you time to scrub it around to remove foreign material. Carburetor Cleaner does the same thing but it is designed to evaporate almost immediately so it will vaporize and burn in the engine. That doesn't give you enough time to do much cleaning. Water between the linings and friction surfaces will generally evaporate before you put everything back together and drive the truck, but when you drive through deep water, it causes one type of brake fade. It's like having a lot of tiny marbles between the two surfaces. The bigger concern is soap. That is a foreign material that isn't designed to dissolve or remove grease or other petroleum products. Once the linings heat up from normal driving, contaminants will soak into them and never come out. That can result in reduced braking power, and / or, more commonly, a brake squeal. The same is true with fingerprint grease on braking surfaces. We try to handle parts only by their edges. Fingerprint grease or any other contaminants can be washed off with Brake Parts Cleaner, and it is acceptable to wash the same stuff off linings, but that has to be done before they go through a warm-up cycle. To say that a different way, any grease or contaminants you allow to get onto brake parts can be washed off with Brake Parts Cleaner while you're still assembling them. Once you drive the truck, it's too late for the pads or shoes. You can wash the rotors and drums, but the pads or shoes must be replaced. Most professionals will even not allow drums and rotors to be washed once they've been warmed up. Those are made of cast iron which is porous. When the contaminants get warm, they soak in and can't be washed out effectively.

Let me add a side note here as long as we're discussing contaminants. Be extremely careful to not ever allow the slightest hint of a petroleum product to get into the brake fluid. That includes engine oil, transmission fluid, power steering fluid, penetrating oil, or axle grease. Most brake system specialists even wash their hands before handling any parts that contact brake fluid. One drop of a petroleum product in the brake fluid can result in repairs costing more than the vehicle is worth. I can discuss that in a lot more detail, but I hope it never becomes necessary.

The vibration you're looking for in the coil springs is very subtle. We would easily overlook it or fail to notice it unless we're specifically looking for it. I normally find that on 4wd or fwd vehicles. Being a 2wd, you have a slightly different wheel bearing design that may not develop the vibration when there's no weight on it. In that case, the Chassis Ear is the best tool to find this. The only other method is parts substitution, but that's the most expensive and least effective way to diagnose a problem. It would be faster and much less expensive to have a mechanic diagnose the source of the noise.

Dandy videos. That is not the normal bearing vibration. From what I can tell, the place I'd start looking is on the splash shields behind the rotors. They sit pretty close to the rotor, as in less than 1/4" away, so it doesn't take much to bend one until it contacts the rotor. You can bend them away with a flat-blade screwdriver.

Less common is for part of the splash shield to rust away, then part of it rubs on the rotor. I've only seen that a few rimes, but there was always enough left to hold it in place once it was bent back into position.

The next thing to look at is the brake pads. On the outside, you can look through the wheel and see the friction surface of the rotor. Look for a rough, or ground-up section, most commonly along the outer edge first. On the inside, you might have to remove the wheel and caliper to see that. Part of the lining will be ground down to metal too on one of the pads. Worn pads get louder when you apply the brakes.

In your original post, you said this is heard above 30 mph. That is a common symptom of the noisy wheel bearing. Worn and grinding brakes are normally heard more at very low speeds

A little noise is normal, but you shouldn't be able to hear it inside with the windows rolled up.

You've covered a lot of conflicting symptoms with many variables. At this point I would go with the Chassis Ear. Obviously you can't run 30 mph next to the truck, with a stethoscope. If you can't find a Chassis Ear to borrow, it would be least expensive to have a specialist diagnose the noise. The best places to go for that are the tire and alignment shops.

If you're pretty sure of which side the noise is coming from, you can try switching the bearing assemblies side-to-side, then see if the noise sounds like it changed location. Leave the rotors on the same sides, but while you have them off, check the splash shields for tiny shiny spots at the bottom, indicating they were rubbing on the rotor.

That play you keep mentioning is not part of this. Noisy bearings can be as tight as a brand new one and still make noise.

I'm nervous about shifting to "neutral" while driving, but as far as the noise changing between acceleration and coasting, that is a real possibility because the engine and transmission will rock back and forth. If you run into a belt or pulley that rubs on something when the engine shifts, suspect a worn or collapsed engine mount. Look for signs that something has been rubbing. Sometimes you can make the noise occur by running the engine, then pushing the vehicle forward and backward while it's in "park". That will rock the engine, often enough to make the noise occur. Of course, if you have a collapsed engine mount, for example, and it's allowing a half shaft to rub on something, the vehicle will have to be moving for that to show up. This is where the Chassis Ear is priceless.

I can mention some other things I've run into years ago that might give you more ideas of where to look. One was the plastic splash shield under the pulleys on older Caravans. One got pushed up out of shape when the owner ran over some large rocks. The water pump pulley would rub on it at times. Another one, also on an older Caravan, happened when the owner ignored the rubbing / grinding noise for almost a year. Turned out to be a collapsed engine mount on the passenger side allowed the power steering pump pulley's lip to grind on the frame rail right next to the fuel line. Some engineer was thoughtful enough to place an anchor clamp for the line right in that spot, so the pulley would have to cut through that metal clip first before it hit the fuel line. That one also didn't make noise when running in the shop.

The weirdest one I ever had would never act up in the shop, and never for the first few miles on a test-drive. Once I got out in the cold winter air, after roughly five miles at highway speed, a loud very irritating whine would show up. It did not change pitch with speed, but it did go away below about ten miles per hour. Of course, by the time I got the hood open, the noise was long gone. I forget how I figured it out, but I verified it by using a piece of string to tie up the separate AC condenser cooling fan blade. Turns out the bearings in the motor were worn but the fan could freewheel when it was warm from being in the shop. Once it got cold, the air flow through it at highway speed caused it to spin and set up the vibration. The only other clue was when it was in the shop, it seemed to spin too easily by hand.

That last one, as I recall, took me a few hours to figure out. That might give you some new ideas to pursue. If none of those ideas help, seriously consider finding a Chassi Ear, especially if you may have use of it again in the future.

I don't have a smart phone so I'm not familiar with the APP you mentioned. Can you use that while driving the vehicle?

Front-wheel-drive vehicles with transverse-mounted engines have the most trouble with engine mounts because they use a different design. One of them also positions the engine and transmission from side to side. On the Dakota, engine and transmission mounts can collapse too, but they cause a lot less trouble.

Chassis Ear. That's exactly the kind of thing they're made for. If you want to do a visual test, look for oil leaking from the pinion seal. If you see that, try pushing the end of the driveshaft up and down. Sometimes a worn bearing will allow the pinion gear shaft to walk away from the rubber lip seal and let oil leak out.

You can try running the engine, in gear, with the tires off the ground, then listen next to the differential. Be careful to not let your hair get caught in the driveshaft. Some people use a long screwdriver to touch their ear on one end and the noise source on the other end.

Be aware, the most common causes of noises from a differential involve the depth of the pinion gear, and the side-to-side adjustment of the ring gear. Setting up an axle is quite tedious and time-consuming, and best left to specialists. The tooth contact pattern is checked with a special paint, then compared to drawings in the service manual. Once properly adjusted, that doesn't change on its own over time, so if you're hearing gear noise, the axle was likely worked on previously and not adjusted correctly at that time.

Wheel bearing noise on a solid axle is not common. It is too small and turns much too slowly to make enough noise to hear. Also, your previous descriptions don't match most driveline noises.

I can't stress enough that you would be done with this problem if you had a Chassis Ear. I just did a search on eBay and found super good deals on a bunch of them. I bought mine about ten years ago for $200.00. Today, I found the same model for way less than half of that, plus a number of other models I've never seen before. One of them has a "Buy it Now" price of only $54.00 with free shipping. That's less than the cost of one wrong part.

With six channels, clip one microphone to the bump-stop bracket right above the pinion gear. That will pick up noise from anything inside the differential. Place microphones on the steel brake lines at each rear brake backing plate. Those will detect noise from the axle bearings. You can place a pair of microphones next to each front wheel bearing too, but since those wheels turn left and right, be sure to route the wires in such a way as the tires won't catch them. You can also clip them to the coil springs when you have that type of front suspension. Coils don't make noise on their own, but they can transmit it from other nearby sources.

As you switch between the microphones while driving, if one is much louder than the others, concentrate on that one's location, and move the others around to various spots in that area, then go for another test drive. In this way, you can narrow down the source.

One thing I noticed with these microphones is they tend to detect noises that are transmitted through the clamps they're mounted to. What I mean is they have to be in contact with whatever is causing the noise. If a microphone is just hanging in the air, or clipped to soft rubber or plastic parts, it will likely not pick up any sound. They are really effective at picking up sounds transmitted through metal parts.

Another source of noise that can be rather elusive is idler pulleys on the engine. They usually DO make noise while idling with the hood open, and we often identify the noisy one with that long screwdriver I mentioned, but with the Chassis Ear, it's easy to show your customer what you found. This too doesn't agree with your previous descriptions, but it's still worth mentioning.

As for removing the differential cover, the only thing you can see visually is a broken tooth on the ring gear. That is extremely rare and would create a different type of noise. Tooth noise also usually changes between accelerating and coasting. If one of the carrier bearings was bad, the ring gear could bounce up and down leading to a horrendous crunching noise.