Vibration only at 45-50mph (1 Viewer)

[DiscoCam]

So I am in the process of finishing up the last few details on my 80 since purchasing 5 months ago. About 3 weeks ago, I started getting a strange vibration. It starts at 45mph and goes away at 50mph. Doesn't matter which gear, but there is less vibration with a lower gear. Only happens when accelerating and going uphill.

I noticed this right after I installed new tires, (Michelin Defender LTX 265/75/R16). I had also installed a 4x4Labs rear bumper a little before that along with my winch. Tires are balanced for sure, had it checked again.

At this point, I am suspecting that maybe somehow my rear bumper is causing the vibration? I honestly don't know. I am at a loss on this one. The truck drives great otherwise.

Here is a list of things that I have done since then. None of them really solved the problem, but they all definitely made the truck smoother.
-New engine mounts
-New transmission mount
-New exhaust mounts
-New exhaust hanger for the tailpipe
-New u-joints front and rear
-dynamatted floor

Should also mention that I am at the end of my baseline; pretty much all fluids, lubricants, perishables, etc have been dealt with already.

Any tips, thoughts, ideas, are welcome. Anything. I have no clue at this point.
Thanks everyone.

 

[ppc]

Even though the tires have been rebalanced it still could be a defective tire, slipped belt etc. Tire balance machines typically spin a tire up to highway speed, ~70 mph. You need to swap tires one at a time until you find the problem tire or get them balanced using a road force balance machine.

 

[DiscoCam]

Even though the tires have been rebalanced it still could be a defective tire, slipped belt etc. Tire balance machines typically spin a tire up to highway speed, ~70 mph. You need to swap tires one at a time until you find the problem tire or get them balanced using a road force balance machine.

Interesting. Is it possible that a defective tire only causes a vibration under acceleration? I thought a tire issue would not depend on accel/decel/coast. Could be wrong.

I will try swapping tires with the spare tomorrow. The spare is new as well. At some point I thought it might be the RR tire and swapped with that and made no difference, but I should be thorough and do the rest.
Thank you @ppc

 

[wrxFTWdey]

My front wheel bearings were both loose and I experienced vibes in the front end. Happened around 35-45 and hills and bumps made it worse

 

[Rifleman]

I know this will sound dumb, but I've seen tire installers do some stupid things. So I'd go back and check the mounting surface on all 4 rims to make sure they are sitting flat when mounted on the axle. Then I'd check to make sure all the lug nuts are tight, and torqued to the correct amount of torque.

 

[DiscoCam]

I know this will sound dumb, but I've seen tire installers do some stupid things. So I'd go back and check the mounting surface on all 4 rims to make sure they are sitting flat when mounted on the axle. Then I'd check to make sure all the lug nuts are tight, and torqued to the correct amount of torque.

Not dumb at all. I wirebrushed every hub and and wheel just in case and no change. And torqued to 85ft-lbs
I swapped each tire with the spare (spare is also new) and did not notice a change.

My front wheel bearings were both loose and I experienced vibes in the front end. Happened around 35-45 and hills and bumps made it worse

Does sound like wheel bearings, but all mine are tight. I didn't replace them since they seemed to all have little to no wear; I packed them with new grease and tightened them back up. Just check today and I didn't notice any play in any wheel.


On another note, I noticed on my tire carrier that I can slide the mounting portion closer to the tailgate by about an inch. In doing so, the vibration seems to have lessened a good bit. So I think I might be onto something here.
I'm gonna check the preload on the bearings in the swingout to see if maybe they can be a little tighter.

Thank you everyone for the replies so far. They have been very helpful. No stone left unturned lol.