Pulsating vibration at from 45 to 65, worst at 55mph. What could it be?

Triple Black · Jan 18, 2020

I have a '02 Ram 2500 5.9L v8 4x4 with a nv4500 that has a pulsating vibration that is worst at 55 mph.

The vibration feel like "vooOOOoom...pause...vooOOOoom...pause...repeat". It cycles about every 1 1/2 seconds at 55 mph. It's getting worst and I can't figure out what it is!

Here's what I know:

The vibration existed when I got the truck in 2016.
I originally thought it was the front wheel bearing. However, the axle nut was just loose.
I have gone through 2 sets of wheels, 4 sets of tires, rotating, balancing, blah blah... No change.
Removing the front draft shaft originally helped. Now there is no change.
Rear drive shaft center bearing was replaced. It was bad. No change.
Rebuilt engine. Worn rings. No change.
Rebuilt transfer case. Front output bearings were bad. No change.
Rebuilt front diff. Axle seals leaked, replaced all bearings and seals. No change.
Both front wheel bearings felt exactly the same to a brand new wheel bearing. (I believe the previous owner replaced both front wheel bearings trying to fix this issue)
Zero vibrations when spun up, with wheel off the ground, to 80mph in 2wd. Did not test in 4wd (front driveshaft is removed and dissembled). There was a racket in the transmission in 5th gear at 1k RPM, that went away at 1.5k RPM.

More details on the vibration:

Pulls slightly when vibrating. Not sure if the pull is from the front or rear.
Vibration is independent of gear or load or engine rpm
Slight changes when turning right or left at speed (changing lanes, going around a bend)
No different when applying normal brakes or the parking brakes.

Known issues:

Alignment is out of whack (tie rod is rusted)
Shocks are bad.
Transfer case tail shaft bushing shows sign wear.
Brake rotors are worn and calipers are sticking. ABS light is on

What it could be:

Warped front brake rotors and dragging calipers
Rear wheel bearing
Rear drive shaft u-joints
Rear diff bearings
Front axle u-joints (the were slightly loose, but still good)
Alignment issue (death wobble)
Shocks
Transfer case bushing
Something else?

Thanks!

Triple Black · Jan 19, 2020

I checked the front brakes and wheel hubs today. Bolts for the wheel hubs were loose, a cotter pin for the ball joint was rubbing against the front left axle, one of the brake hardware was on backward scraping the top of the rotors, both dust shields were rubbing against the rotors, and the wheel speed sensor wires were cut. I fixed all those issues. The front brakes feel solid, no more front end noises, and the ABS light went out.

I failed to mention (in my huge post) that there is a strong hopping in the left rear at 40 mph which smooths out at 45. I'm suspecting that might be the cause of the vibration. I'm going to order rear wheel bearing for both sides to see if that resolves the issue.

Triple Black · Jan 20, 2020

Another update... I strapped the front output shaft so it wouldn't move (driveshaft is removed). This stopped the transmission from shaking and made it clear the left rear wheel bearing is bad. I found 1/16" of play back there on Saturday. It should only have 5/1000th of inch of play! There's also clearly a death wobble in the front.

Next step, order all new steering linkage, inner and outer wheel bearings with seals for both sides, and change the rear gear lube.

Pulsating vibration at from 45 to 65, worst at 55mph. What could it be?

Triple Black

Junior Member

Triple Black

Junior Member

Triple Black

Junior Member

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