Mystery vibration at 60 miles per hour

Last week my truck started vibrating when my speed was around 60 miles per hour.
The steering wheel does not shake, the gear shifter and transfer case shifter do not vibrate.
I can accelerate above 60 miles per hour, place the shifter in neutral and allow it to coast to 60 miles per hour and there is still a vibration but the shift knobs and steering wheel do not.
It does not vibrate below that speed or after that speed and I only feel it in my seat and the floor board.
I put my brand new tires on it and took it for a test drive and it still has the same vibration.

I have an appointment for a front end alignment tomorrow, I hope that helps.

UPDATED HISTORY
Last week I drove 240 miles to do military training, there was no issue driving down. I drove around town a couple of days just to get things to eat and such, still no issues.
On my 240 mile drive back home I noticed that I was getting a vibration when I was coasting at highway speeds. If I accelerated the vibration went away, if I let off the gas the vibration came back.
When I got home I crawled under my truck to drop the center section so I could grease the double cardan joint, I was wondering if this might be the issue. (My drive line is a Spicer unit and does not have an accessible grease zert on that joint, I have to use a needle adapter.) When I removed the two bolts from the carrier bearing I noticed it was substantially warmer than the rest of the drive shaft and u-joints.
I replaced the carrier bearing with an almost new one from my old driveshaft, it spun very freely. I also replaced my front outer tie rods and swapped in my new octagon alignment cams. Hence the reason for the alignment appointment tomorrow.
I purchased a new set of tires several months ago and had them mounted on an extra set of 4Runner wheels. After installing my new wheels the vibration is much less then the old tires. But I still have the vibration in the floorboard, seat and gas pedal. There is NO vibration in the steering wheel or the gear shifters. I'm stumped.

 

I suspected you have a bad carrier bearing or U joint in your drive shaft.

 

I replaced the carrier bearing with an almost new one from my old driveline, it spun freely...
I would expect the transfer case and transmission shifters to vibrate if it was in the driveline, but they are smooth as glass during my butt massage at 60 MPH.

 

Any chance there is wheel damage, or wheel warping from incorrect torquing?

 

Not sure, the new tires I put on this morning are on a new set of wheels. So I doubt that is the problem.

 

Just to clear a timeline up:

At some point previously, you've changed your carrier bearing (with a used bearing),
then you got a vibration (last week)
then you got new wheels and tires today (did not alter vibration)

Right ?

So you're assuming that changing out the wheels and tires crosses those off the list? I'd ask the shop to balance them at least once more, or have them road force balanced at a shop that offers that.

While you were changing the bearing, did you grease and inspect the u joints as well? What brand bearing? Non-OEM/Spicer bearings are notorious for failing quickly.

Vibrations suck, and there is rarely a smoking gun.

If an alignment doesn't solve it, you're in for a long frustrating road.

 

I updated the original post and answered these questions. I'm not sure if any of the local tire shops do a road force balance.

 

Thanks for the more detailed history. It helps a lot when making suggestions online.

Because you notice a difference when accelerating vs coasting, I'd consider checking some of the other bearings. Wheel bearings, etc.. The diff bearings will be a little bit more tricky... I had bad front wheel bearings that didn't have any perceivable movement (up, down, diagonal, etc) at all, but did make a slight vibration under acceleration while turning. I tried many cheaper alternatives before biting the bullet on changing them.

I also recently developed a newer vibration, which ended up being rear brake drums (I had them turned at a shop when I rebuilt my axle).

 

As a general rule, when I feel a vibration in the seat the problem is toward the rear of the vehicle. A steering vibration indicates a problem in the front. So, even though your driveshaft center carrier bearing spun free, that only indicates a good bearing. Has the rubber isolator holding the bearing in become worn? Couple things to try. Move the rear tires to the front and vise versa. If you now have a steering shake you have a tire/rim/balance issue. Or, carefully support the rear wheels off the ground following all safety precautions. Have someone put vehicle in gear and look for a bad rear tire, bent rim, or drive shaft not spinning true. In rare cases I have see the balance weight(s) missing from the driveshaft. Keep us posted.

 

I was thinking about placing the rear axle on jack stands and spin the tires at the prescribed speed. Safety first of course!

 

Well I feel stupid!
Placed the rear axle on jack stands and had my son put it in gear. The rear flange at the rear pinion had all four bolts loose.
I tightened them up and took it for a drive, no vibration!

 

Call it a learning experience. Glad the "raising the wheels up and putting it in gear" revealed the easy fix. Remember- seat vibrations = rear of vehicle. Steering vibrations = front of vehicle. That's divides the location in half- almost. Thanks for posting your findings and results. Cheers.

 

I also have been dealing with vibration problems. Why would a vibrating shifter indicate a driveline (driveshaft?) problem? My shifter definitely bounces around and i can generally feel my vibration in the shifter knob.

 

ztwatson-
Is the shifter "bouncing around" like it's loose, or just vibrating when driving down the road?

 

Phessor,
Glad you found your problem! Let us know how your alignment goes with the new octagons & bolts installed. I am sitting on the fence with those. IIRC, the manufacturer stated that most all have the front octagon in the middle and the rear all the way out. The pic you posted of your octagons appears to be set up in that fashion. But I/we would like to hear your first-hand experience on what worked for your alignment. TIA!

 

It bounces around when i hit bumps or as the truck jostles. When driving on a smoother road I can feel the vibration both in my seat and with my hand on the shifter.

 

ztwatson- Hard to narrow down based on what you said. You have a shifter bouncing around and a vibration. That can be related or two separate issues. I would start with taking a good look at the transmission mount for the bouncing shifter. If the shifter lever is actually sloppy I would look at the shifter lever seat that sits in the top of the tranny. They are prone to extreme wear. The shifter end bushing is also a high wear item. The pn's may be 3350535020 and 3354831010. Verify of course, but search these numbers and it will give you an idea if what the parts look like. Cheers

 

Glad I found this thread, having the same issue. Going to 60 mine start shaking, going to get balanced first and alignment. Hopefully that fixes the issues.