Vibration felt in rear of truck
 

I have a 2002 Quad Cab 4.7L 4WD 6'3" bed Manual transmission that has a vibration issue I can't figure out. Here's what I know...Vibration begins around 65 MPH. It is always there, but the severity of the vibes goes up and down, and I can't find an obvious pattern as to why. I can go down a steep hill and put the truck in neutral, letting the engine idle, and the vibration remains at 65 mph or higher, so I don't suspect engine parts or flywheel. It isn't tires or wheels. I replaced the tires when I got the truck, because they were old and rotting in the sidewalls (good tread though). Anyway, the vibration continued with the new tires. I tried throwing on the wheels/tires from my 07 Durango (wrong size tire, but the wheels fit) and the vibration continued with the Durango set. The motor mounts seemed ok, but the transmission mount was replaced due to the rubber found dis-bonded from one of the plates. Tranny mount was no help. I had the (one piece) drive shaft balanced and both U-joints replaced along with the transfer case tail shaft bushing - no help! I understand the differential had been rebuilt due to a pinion bearing failure. The fluid looks good, but I get some gear noise occasionally, especially when exiting the freeway or coming to a stop. The noise isn't all that bad, but it's noticeable if you are listening for it. I took it to another very reputable drive line shop, and he told me he could re-work the drive line and charge me a lot of money, but it won't fix the problem. On a test drive, he drew on his experience to say that it feels like tires, wheels, or something that produced a slower up/down shake than a drive shaft would produce.There was doubt the differential or even transmission parts would cause the vibration at that frequency- plus it seems to me the gears don't have the mass and weight to produce the sometimes intolerable vibration I get. I even put new shocks on. It rides better, but the vibration is still there. About the only thing left that I can think of is maybe a bent axle shaft or something in the hub/brake rotor area. There is nothing felt in the front end at all. The steering wheel is rock solid and I also removed the front drive shaft for giggles. Turns out it doesn't rotate anyway in 2WD mode. I've also noted the shift lever slaps back and forth with the same severity as the felt vibration...I'm at a loss of where to go next. Any ideas???

Disc brakes with internal drums for e-brake, right? Check the adjustment on the e-brake, I had one truck that wouldn't vibrate at all, till you had been driving for a bit.... the e-brake was adjusted too tight, and it would heat the drum/rotor feller to the point that it would warp, and the vibration would start...... stop to see what was up, and it would have enough time to cool, so, no vibration again for a little while....... That one was FUN to find.

If it is more consistent, I would be tempted to jack up the rear, and check the wheels/rotors for runout. Doesn't take a lot to make a horrid vibration... that would be consistent though..... you would get the same vibration at the same speed, each and every time.

It may be an axle bearing........ but, you should be able to feel that if you spin the tires by hand.

From what I'm reading I may not be helping much, but my father had a vibration only at 65+ MPH with his 02 equipped with the 4.7. Turned out to be his rim was a bit bent from being used on a car lift that was too small and that mainly caused the vibration on the highway at high speeds every time... I think I had a similiar issue on my truck before I sold it and it was also an 02 with the 4.7.

The tires and wheels were changed to a different set temporarily and the problem persisted from the OP.

I know you had the driveshaft balanced and u-joints replaced but have you tried a different driveshaft?

I'd test the runout of the axles first. Make sure the surfaces are good and clean. A little rust under there could cause things to be out enough to possibly cause a vibration.

I had a bad vibration in mine starting at about 40,000 miles. The right front hub assembly was bad. Replaced it and the problem was better but still vibrated. Turned out to be a bad tie rod end. Replaced it and it was perfectly smooth at all speeds. Still is at 180,000 miles.

i just went through a vibration that showed up around 65. i balanced tires, did ujoints to no fix. it was a front hub bearing assembly.

Thanks for the responses. Sorry I'm so slow in replying. It'll be a couple of weeks until I can give attention to this again. The warped brake rotor/drum is an interesting idea - I'll definitely check that out. I tried to find a different driveline, but local junkyards can't figure out how to move a vehicle using a forklift without damaging driveshafts - and at this point I'm not willing to spend the dollars for a new one. I neglected to mention in the first post that I had already removed all the wheels and cleaned both mounting surfaces (wheel and hub) with a drill and wire wheel. They weren't that bad, and it didn't help. I've already placed the truck on jackstands and with engine running in gear, I didn't see any wobble to speak of. There really wasn't any wobble at all between the inner wheel surface and the fixed brake caliper - there is a 1/2 inch or so between them.

But I think I'll re-visit the differential too. If it wasn't done right, maybe that's been the issue all along. I've finally noticed a pattern during my short commute. Occasionally there isn't any vibration, but it returns when going around a curve in the road. Maybe the "differential" rotation in a turn is affecting how it vibrates. More to come...

When you mention that it returns when going around a curve, it really does sound like it's developing from the differential/rear end area.

Again, thanks for the replies. I'm still fighting this issue. I got inside the differential and found that the gear lash was very loose. I believe the spec was .006", and it was around .040 or so. The running torque of the pinion seemed ok (at around 20 in/lbs) so I left that alone, and adjusted the bearing adjusters until the pinion/ring lash was very close back to spec. The slight gear noise is gone, but the vibes remain. But now it doesn't seem as severe. Maybe there are multiple issues conspiring to frustrate me! I rotated the tires (again) to see if it makes a difference. I'll find out in the morning commute. I also jacked the truck(again) and with it on jackstands ran it at 75-80 mph. The driveline, u-joints, differential, and transmission appear to be smooth as butter, and I felt no vibration (while stationary on jacks). Even though the felt vibration while driving is in the seat, along with the shift lever still slapping back and forth, and it seems to come from the rear, could it be from the front?? I'm now wondering about the front axle or CV joints. I don't have the front axle disconnect feature, so the front axle constantly rotates. In 2WD mode, only the front driveline doesn't rotate, I sure don't feel anything up front though. I had an old army helicopter mechanic ride with me, and he used a vibe analysis trick using a pencil. He noted the vibes are vertical, not sideways or otherwise erratic. Thanks again for the replies. I'll try to keep this updated and will post a fix if found.

OP here - it's been awhile, but I had to just deal with the vibration for a few more months before getting it figured out. In mid-2020, I took it to a couple of places that couldn't figure it out either. Then one large shop (trucks, semi's etc) took a look, and found the problem. It seems I was being taken for a fool with the steering being rock solid, and the steering wheel had no vibration. I just didn't believe it was coming from the front end, but it was. On my truck, there is no locking hubs (Axles turn constantly). With the front differential being offset to the drivers side, there's something called an "intermediate shaft that is about 8 or 10 inches long on the drivers side, and one about 2 feet long on the passengers side. These are just splined shafts that connect the CV half-shafts (which are identical left and right) to the differential. The splined intermediate shaft fits into a "socket" of the CV shaft. These were all "wallered out" , and should have been very easy to find by just crawling under the truck and wiggling by hand. It sure didn't feel like front-end problems, but it was. Hope this prevents someone else from looking foolish.