vibration

1996 Fleetwood Southwind, F53 Ford, 35 ft. At about 40 to 50 mph I get a vibration, smooth except for that speed. Did it with the old tires, does it with new tires. Feels like a bad universal but they look fine, I grease then often, no play that I can find, no rust around any of the caps. This is the first vehicle I've owned with center support bearings, it has 2 of them, and I don't know how to tell if they are OK or not. Nothing is obviously wrong. I can lift one of them about 1/4 inch, maybe less, looks like maybe the rubber part of it has partially failed? No unusual noises. MH has 123,000 miles, I've put about 50,000, don't know if they were replaced before I bought it. Thanks Much.

;D Don't drive between 40 and 50    :

It is possible, but not common, for something like a brake hub to be far enough out of balance to cause this.  I am grasping at straws, though.

I don't know how close my experience is to yours, but if you're talking about those bearings that hold the driveshaft up, I think replacing them is worth a try.  I have a 1972 GMC truck with one of those support bearings.  Every 10 years or so, the vibration gets pretty bad and when I finally think of replacing that support bearing, I can't believe the difference.  The way I remember it, there is no play in it when the support bearing is new.  It won't move a quarter inch.  I'm not a mechanic, though.

I have thought about going from 40 to 50 real fast but the poor old thing doesn't have real fast. It's been going on for about a year, maybe more, so I don't think a hub is the issue. richardhufford reply is encouraging, I've never changed one, perhaps a new adventure. Thanks, Bill

One quarter of an inch is a worn carrier bearing. It shouldn't have any play just like a u-joint.

That's a lot of miles and years on those driveshaft carrier bearings.

Vibrations are symbolic of a soon to fail bearing.  Replace both of them before the driveshafts come apart and do some damage.

Make sure you phase the driveshaft if you take them apart. Three drive shafts will be mighty expensive if it comes apart, might take the trans with it too. If it were mine, it would have all new universal joints and carrier bearings, with those miles and a vibration. 

If it?s in the driveline, the vibration will change exactly between the + and the -. + being when your foot is on the accelerator putting power to the rear wheels, - being when your foot is of the accelerator and rear wheels are driving the engine. Driveline vibes usually disappear in that sweet spot.

Charlie 5320 said:

Make sure you phase the driveshaft if you take them apart. Three drive shafts will be mighty expensive if it comes apart, might take the trans with it too. If it were mine, it would have all new universal joints and carrier bearings, with those miles and a vibration. 

Click to expand...

^best advice given on this topic^. Replace them all and be done with it.
I've had a u-joint vibration before and the u-joint looked and felt great until the driveshaft was pulled.

Charlie 5320 said:

Make sure you phase the driveshaft if you take them apart.

Click to expand...

This is what he means by "phasing".

https://www.youtube.com/watch?v=dt69zYAcXME

You can drive through the vibration and it goes away over 50 MPH?

jubileee said:

If it?s in the driveline, the vibration will change exactly between the + and the -. + being when your foot is on the accelerator putting power to the rear wheels, - being when your foot is of the accelerator and rear wheels are driving the engine. Driveline vibes usually disappear in that sweet spot.

Click to expand...

^^^ What Jubileee said!

Take your rig up to harmonic point then let off the gas. There will be a brief moment the vibration is lessened or goes away as the force is relieved from the driveshaft u joints and bearings.

Its the driveshaft support bearing.
My dealer replaced all tie-rod ends and completely rebuilt the rear end before they figured it out  : I paid for all the new parts but he absorbed the extra labor costs

I agree with the group that says one of the carrier bearings, or the rubber support housing, is bad. Should definitely not be a 1/4 inch of play. To properly check drivetrain components ((u-joints, carrier bearings,etc) you almost always have to chock the vehicle and put the transmission in neutral. This takes the strain off the drive train, while in park or in gear it sometimes holds the drivetrain tight and hides a bad universally joint or carrier from being detected. But usually in a drivetrain problem it shows up when you let off the throttle, and that?s when a vibration really shows up. A vibration range at specific MPH is almost always a tire balance issue. One of my first jobs was in a tire store and customers would come in wanting new tie rods or ball joints because they felt vibrations in the steering wheel. We always did a tire balance check first and in the time I worked there, a vibration at certain speeds felt in the steering wheel was never a bad tie rod or ball joint, every time a balance issue. I realize the OP had tires replaced and the problem remained, but all tires balancers and tire tech?s are not equal. At the shop in the old days, we had a bubble balancer, and a spin balancer. The bubble balancer was cheaper so many people opted for it. I never new why it was cheaper because you had to pull the wheels to do it. I was just a grunt and did what I was told. But back then, the spin balance machine was WAY more accurate than the bubble machine. I don?t know how they balance tires now, probably with lasers or something. But I wouldn?t totally rule out a bent rim or something. I had wheels that would balance properly on the bubble, but couldn?t get them to balance on the spin machine until they replaced the rim. Just another point of view from an old dude. ?

The spin balancer we used back in the late 60's,  was it spun the wheel on the car (up to 60+ mph) using a strobe light and a mark on the wheel with a magnetic pic-up,  it ballanced the whole rotating assembly...the tire/wheel,  the brake drum, lugs, hubcap as a unit.

IMO...It was better than how they ballance wheels today.

Yep Tony, that?s the time era I speak of. Unrelated to the original post, I have to tell this story. At that time I had a 57 Chevy Nomad station wagon. (Wish I still had it) I put some new wheels on the front called chrome reverse at the time. After I did that, occasionally one or both of the front tires would go flat. Could never find any leaks any they would stay up for a time and go flat again while I was driving. I mean I could never find a leak and I worked at a tire store for goodness sakes!! One night at work things were slow so I decided to pull my car in and balance the tires. I put them on the spin balance and when I quit, the tire was flat. I did this a couple times, and each time the tire went flat. I finally noticed that at high speed on the spin balancer, the tires would elongated and pull away from the rims and release the air. The rims were too wide for the tire!!! There is always an answer to every mystery.  ?

Took off the section of driveshaft with the support bearing that had some play in it. The bearing is fine but the rubber part of it has collapsed some on the bottom side. Universals are very good.  Will continue Monday. Thanks All

Windybill said:

Took off the section of driveshaft with the support bearing that had some play in it. The bearing is fine but the rubber part of it has collapsed some on the bottom side. Universals are very good.  Will continue Monday. Thanks All

Click to expand...

Another .03 ? If you don't know if the U-joints have ever been replaced, and the Carrier Bearing rubber (dampener/seal) has collapsed (not good).. at 21 years old (if OEM). And with the work you've done thus far.. A New set of U-joints, and Carrier Bearing.. along with Cleaning and Re-greasing (marine grade) the Slip Shaft assembly (new seal too).. Might Be The Way To Go ? For Safety.. and Piece of Mind ??