control arms are more of a clunk, not a grind.

You've taken both hubs to 185 ft-lb, correct?

Just for shish, grins, laughs, and giggles

Put the truck in neutral with parking brake off
jack up only one rear corner
spin the tire and feel for any roughness
put that corner on the ground, jack up the other corner
spin the tire
any difference?

With one tire on the ground and you spinning the other, it should spin the driveshaft. This will isolate the wheel bearing for each side, the pinion bearing, and the spider gears and rear wheel bearings.

"Hypothetically" if it was something in the rear, it would make the same grinding at speed as it does when turning. *However*, if the issue is in the spider gears, it will only come to light when they are active, which is a differential speed situation.

*Note: will not work with the limited slip differential unless the clutch pack is trashed

 

Yes, both sides are torqued to 185ft-lbs. Amazingly enough, when I re-rented the torque wrench from autozone, it was still set where I used it last week, no one had borrowed it since then.
Fun that you should reply that, I was just about to edit my response to include this test. However, I did it a bit differently, by picking up the rear end completely. I tested spinning the tire from both sides either way as fast as I could and listened for spider gear chatter. I then had someone hold the opposing wheel and spin it in both directions, testing both sides as fast as I could spin the tires.

Everything, from what I could hear, was absolutely silent. The only noise made was swapping directions, and it lightly clicked one time as the gears changed directions. I'd assume if the spider gears were worn or had too much tolerance, it'd happen in either direction and not just one?

EDIT: On my way home today, I tried to take lefts harder than usual (most of the turns I make are rights though, go figure). I could just barely make out the noise. I used to be able to actually 'weave' in my lane and make the noise just barely audible/felt. No matter what I did today, however, I could not get it to be loud enough to really discern from road noise. Almost like it's just deciding to go away on its own slowly, I wonder if maybe it was caused by all the recent rain/possible mud. Also a better description of the noise is kinda like a vibration/dull tapping. I almost thought it was the bed rattling against the framerail with rubber between it (it's not a metallic sound). I hate when diagnosis is just "gotta drive it" especially on my way home I saw a Ram 1500 with a 45'd front left tire on the side of the road, obviously the lower balljoint snapped.

 

In your tests, did any of the combinations spin the driveshaft?

a vibration/dull tapping makes it even more un-pinpointable

 

When you pulled off your rotors were they discolored kind of black blue?

Because buy the looks of your hub they got cooked by dragging brakes dragging brakes create enormous heat that transfers into the hub assembly cooking any grease in the bearings and destroying the hub seals.

That's what destroyed my last hub lucky for me the hubs were due to be replaced anyway.

 

No discoloration or overheating. Both sides have even pad wear, still almost 1/2" material on both pads, both sides. I changed the pads and rotors about 6 months ago. I don't think the brakes drag, as I was able to remove the brakes and rotor almost immediately after I got to work, they were not very hot.

For now, diagnosis will have to wait, I just ordered me a cheap camera I can strap under the truck to try at least identifying front/back before moving on. No need to throw more parts at it yet

 

Back when you changed/replaced the pads and rotors do you remember the color of the rotors?

Dragging brakes wear normal dragging front brakes is a common problem with the Dakota not fully understood.

That hub in your pic's is cooked good it got extremely hot somehow.

The 98 Dakota has the worse disk brakes ever low quality small pads from 99 to 2002 they improved the front brakes considerably then from 2002 to 2004 they were improved again.

Only the 98 Dakota had crap disk brakes

 

My previous rotors looked fine as well, they were almost new looking (minus standard rust on non-contact areas, it wasn't worn deep in the pad areas), I just got a habit of doing rotors with pads anyway. However: for the drivers side hub, it does not account for the 170k the previous owner put on it. I don't know their braking habits, and it smelled very burned. The passenger side hub didn't smell burned at all, just the grease that leaked out was a little black. Worth noting that both hubs actually felt good before removal, no slack, no sound, or grinding feel when spun by hand. I might still have the old rotors, I have a rack where I work that I tend to just toss my old parts on and never really get rid of them.

 

Dakaz, I am not seeing the heat discoloration that you are. It looks more like rust to me.

 

Now I have an additional thing to fix... Drove the truck in this morning and someone carpooled with me. They said the sound was like a wobble to them. Figured it couldn't hurt to check the lugs, especially on the passenger right since it's the only one I've not had off recently, or tightened myself (last time that wheel was off was last time the tires were rotated by the tire shop). Both fronts have been done by me in the past week+ 'cause of the hubs. Driver left has been checked by me/rebuilt when I replaced that rear brake line (and replaced that wheel cylinder). So it's the only one I haven't messed with in recent months.

Tried to tighten them (they were torqued fine) but moved the truck a little.... aaand my truck sounds like a cheap motel bed. :I Everytime I gently rocked the truck, squeak, squeak, squeak. I've been having a light squeak/click during light braking (one reason I changed the front brakes/rotors on the front) yet never felt it through the pedal. I guess I finally parked it on the 'touch' section, and with the parking brake engaged, let it reach. So I know where that sound is coming from now.

Great thing is: I ALREADY have the brake kit and shoes for it from redoing the left. I just never got around to doing the right side. So at least I don't have to buy anything new for that, just need a warm day. I'm going to be a bit mad at myself, yet extremely relieved if I pull that drum and find say, an over stretched spring, unseated pad, or similar that maybe was flopping over the shoe on left turns and grinding against the drum.

EDIT: Another idea that came to mind (and would sorta explain why it only happens during left turns, and has quieted down a little) is maybe drum corrosion/rust. It been raining or drizzling almost every day for over a month, yet to see 3 days with no rain in a row since November. That could have caused a buildup of rust around the lip between the drum and backing plate, so when I do a turn and put load on the rear axle, it moves just slightly enough for the drum to grind against the backing plate. Would explain intensity vs hardness of the turn too, harder turn, more loading, closer and rubbing harder. I googled it and found a video on youtube from some ford channel explaining that very thing, he said it can sound like a wheel bearing going out and manifests during turns (for load shift).
I'm not very optimistic about either of these being the cause, but I wont know for sure until I take it apart.

 

Another bit of an update, since it's easy enough, I redid the differential test following magnethead's guidelines. Again, everything was absolutely silent. Tested both sides, spun as fast I could in either direction, and crawled under the center to do the test from underneath to be closer to the diff.

Here's a (horrible) video from the passenger side

I didn't bother recording the driver side since it was the same exact result. Theoretically, spinning the passenger side has the same effect as a left turn, the right tire has to spin faster. In this case, much faster vs a non-moving... The only thing I can think of that this test doesn't bring into the equation is the lateral load. While I did this test, I made note to check a few tolerances. Driveshaft backlash seems to be 1/8" or less of turn before it turns the tires. Could just be the add up between pinion and spiders from one extreme to the other? From what I've read this is about normal. I also tested moving the axles in/out, they move enough to be noticeable, as in you feel and hear a light clunk, but can barely make a visible notation, so maybe 1/16" lateral play? Again, a lot of forums say this is normal with a c-clip setup. (some say they have over 1/4" of travel, which to me kinda sounds bad). I also tried spinning from both sides pushing against the tire, and pulling it, all was smooth. Took a chance to look behind the passenger drum, doesn't LOOK to have any edge buildup, but I can't see past the lip.

Going to try to remember to throw the brake kit and shoes in the truck when I get home tonight and change it all out during lunch tomorrow. If the noise/vibration continues after that, I guess I'll have to wait until that camera comes in and record a video from under the truck. Its ETA is this weekend, but it'll be raining, so I can't do the test.

EDIT: On the way home we formulated an idea that was closer cause the sound actually really presented itself. He mentioned something about wheel hop, but I thought it was closer to a dull rumble strip sound/feel.