MYSTERY shake KINDA

[blacklightning]

2018 single cab 4wd Express.
Bought this thing and knew it had shake, hard pass up, things practically new inside out upside down. Priced right. Anyway. Maybe some regret.
I rarely go over 65 so it's not a big deal, I'm blown away that I'm getting solid 24-25 avg mpg out of this hemi. Paying for itself.
Shakes above 65-70.
First thought was tires.
Till I set the cruise on 75 and realized the shake comes and goes.
Predominately, itll shake going uphill, smooth out downhill and flat road is mixed bag, may or may not shake.
With that said, it'll sometimes do the exact opposite.
I did turn MDS off, set cruise and it still randomly shook but not nearly as bad.
So I've searched, read something about torque converter lockup and something about about dampers.
Been busy, so haven't had time sit ponder much, did have time write this novel but figured my symptoms are pretty specific but no searches matched.
Ive check driveshaft play, u joints, CV axle, but it's fact it smooths out that tells me it's probably none of that.
Any thoughts appreciated.

 

[blacklightning]

2018 single cab 4wd Express.
Bought this thing and knew it had shake, hard pass up, things practically new inside out upside down. Priced right. Anyway. Maybe some regret.
I rarely go over 65 so it's not a big deal, I'm blown away that I'm getting solid 24-25 avg mpg out of this hemi. Paying for itself.
Shakes above 65-70.
First thought was tires.
Till I set the cruise on 75 and realized the shake comes and goes.
Predominately, itll shake going uphill, smooth out downhill and flat road is mixed bag, may or may not shake.
With that said, it'll sometimes do the exact opposite. Or it just doesn't seem stop shaking.
I did turn MDS off, set cruise and it still randomly shook but not nearly as bad.
So I've searched, read something about torque converter lockup and something about about dampers.
Checked u joints, CV axles basics but something's telling me it's none of that.
Been busy, so haven't had time sit ponder much, did have time write this novel but figured my symptoms are pretty specific but no searches matched.
Any thoughts appreciated.

 

[Mojo88]

......
I did turn MDS off, set cruise and it still randomly shook but not nearly as bad.
So I've searched, read something about torque converter lockup and something about about dampers.
Checked u joints, CV axles basics but something's telling me it's none of that.
.......

Here's the thing with 'shakes' at highway speeds.............. don't overthink them. Most of the time it's gonna be u-joints, CV joints, wheel bearing, wheels, or tires. And often times it's difficult to confirm that a part is bad. You may crawl underneath and try to wiggle the u-joint, and it feels solid. But eventually you take it apart and you see that it's bad (but hasn't quite exploded).

Anyway, I would focus on those five basic things: u-joints, CV joints, wheel bearings, wheels, or tires.

My suspicion is that when you set the CC, you introduced a more consistent speed, which lessened the vibratory effect. Versus you working the gas pedal with your foot, where there would be more fluctuations in speed/rpm and it sounds like the shake is very sensitive to all that.

 

[blacklightning]

Setting cruise caused the vibration to become more consistent.
Generally downhill smooth, uphill shake, level ground mixed bag.
I even put trans in neutral and it still shook
It's not a, I think it's shaking, it's a, the center console is about to come off it's mount shake..

I'd think if it were balance issue with tires or driveshaft, 75 is 75 going up or downhill, so for it to smooth out like silk going downhill, seems odd. Then go uphill and have center console try beat my leg like I owe it money.

Did put weight in bed, not much couple hundred pounds on end bed and seem the shake came on earlier.

Hopefully it's just balance or bad rear tire.

 

[Wild one]

Setting cruise caused the vibration to become more consistent.
Generally downhill smooth, uphill shake, level ground mixed bag.
I even put trans in neutral and it still shook
It's not a, I think it's shaking, it's a, the center console is about to come off it's mount shake..

I'd think if it were balance issue with tires or driveshaft, 75 is 75 going up or downhill, so for it to smooth out like silk going downhill, seems odd. Then go uphill and have center console try beat my leg like I owe it money.

Did put weight in bed, not much couple hundred pounds on end bed and seem the shake came on earlier.

Hopefully it's just balance or bad rear tire.

Has the truck been lowered or lifted,as the way your describing it,it makes me wonder if your pinion angle is a bit wonky,i also wonder if you might have bad bushings in the rear locating arms

 

[Jeepwalker]

How mechanically inclined are you?

If you have the gusto...put it up on jackstands, all 4 wheels. Lift up on the rear wheels. Rock the front wheels 6:00->12:00 positions (rock HARD like you mean it!). If those are good, inspect steering and ball joints (watch some how-to videos). Get under and shake the front/rear Drive shafts like you MEAN IT! Lift up/down on the front half-shafts. If that all looks good, start trk, put vehicle in gear and 4x. Watch the wheels and tires as they spin. Anything shaking ..moving in/out? Be safe... that stuff has rotating mass. Have a buddy give it some 'gas' and see what's shaking. Stay away from the wheels/tires as they turn. You'll see if a wheel/tire is really shaking/wobbling, there you go. Look REAL careful at the wheels for any 'movement' mis-shaped tire, bent wheel, etc.

Could be:
-Bubble on a tire
-Tire weight fell off, or tire out-of-round.
-Someone put on a cheap parts-store front hub and the flange came pre-warped (I had one like that brand new ...warped, out of the box!). Maybe the one I sent back worked its way down to a parts store near you!! LOL.
-Bent driveshaft or weight fell off driveshaft
-Front driveshaft flaked-out (if 4x4)
-Bent rear axle flange.
-Pinion bearing failing
-U-joints going bad, or not installed properly
-Bent rim (hit a curb ...or who knows what??)
-Driveshaft output bearing/bushing severely worn (doubtful)
-Front axle bearing or CV shot.
-Severely worn front bearing/hub assembly (but that should make noise).
-Former mechanic didn't get brake rotor on properly or some big debris behind rotor.

Those things don't cost much or anything to inspect on your own. Open hood and see if the engine is shaking? If you don't know what yer doing, or don't feel comfortable or competent digging in, take it to a shop. Should be easy to ID.

Good luck

 

[Tominator223]

I’d look at bearings & u-joints. Uphill bad. Downhill ok. 1 bad needle or roller bearing.

 

[Marshall]

I have changed quite a few u joints over the years that looked OK and you could not feel any shake, but they where full of dried grease and rust , sized up.
Going down hill, you have no load on the drive train, but with load or up hill, you have everything under load.
If you shift to N when at speed , its smooths out?

I have never seen a bad T.converter, Not something I have ever messed with,
so no idea on that. As its a used truck, no history on the last owner?

May not be that, but I would start by pulling the shaft, then also check rear end while shaft is out.

Tire problem should change if you rotate all the tires /wheels front to back.
Wife's car with new cheap tires , had a pull to right and not smooth.
They put that on the back and it was fine, but I made them put it some where else and install a different one.

 

[Marshall]

PS, Just a thought on tires, if a balance don't show anything, don't always show up a bad one.
Any friends with a ram ? if so try switching wheels on a weekend and see if the shake moves to the other truck, if so , bad wheel or time for new tires.

 

[ReddJackson]

I’m not a wrench, probably not as knowledgeable as the majority of the members here, that being said in my personal experience when I’ve had shakes at speeds 60mph plus always turned out to be Front End Alignment

 

[aszumilo]

I had a mystery shake on my 2004. Doing 60-65 (or around there), applying the brakes, I would get a pretty good intermittent shake. Felt like something in the rear was vibrating. New tires, Front End alignment, rebuilt rear differential, new U-Joints, new brakes and rotors all around. Never could find what was causing the issue. Dealer couldn't find it, drive line shop couldn't find it. Lived with it for a couple years, till I wrecked it.

 

[hogan1945]

Years ago my impossible vibration was a rear bent rim, and it was new from factory when i bought the Ram???

 

[iWolfRam]

Your description of vibration is exactly, to a T, what has been happening with my 2014 since I bought it with 50k on it. I’ve tried many parts, alignments, new tires, etc. Recently had a very well trusted master Mopar mechanic inspect everything that might cause the vibration, and he couldn’t find anything.

The ONLY thing left, in my eyes, is driveshaft out of balance / or something out of whack internally in the transfer case. At this point I’ve driven the truck 46k additional miles and gotten used to it. Annoying AF, but it hasn’t gotten any worse in that amount of time. It’s my only gripe about my truck, though.