After replacing carrier and pinion bearings in the rearend, transfer case output housing, and 3 driveshafts, I thought the CV would get rid of my vibes. It didn't.
Not sure where to go next other than a car lot. The next three things I can think of other than trading it in are rear wheel bearings, companion flange on the rearend, or the transfer case.
Aggravated.
The vibes start at 58 mph and are worst between 65 and 70. 74mph is not so bad. 90+ it gets better. If I rotate the driveshaft on the rearend (clocking) it does change somewhat. This X had documented vibes starting at 35,000 miles. I didnt find that out until after I bought it and tried to fix it. It had vibes when I bought it, but the rear ujoint was worn and I thought that was all of the problem. I have had 3 SuperDuties and no vibes so i didnt research enough evidently. Can rear wheel bearings cause this? Never worked on a floating axle before. The vibration could be interpreted as a rumble. The rear axle is dead quiet until 58 mph.

 

You need to mount a video camera under the truck and SEE what the heck is vibrating. I would also try different air pressure in the tires and see if that has any effect.

 

Thanks katiesdad7. The X has had two different sets of wheels and tires. It is definitely mechanical.
I should better describe my problem.
When accelerating, the X is smooth until about 55. It then starts rumbling and vibrating through the vehicle. I can feel it in the gas pedal and sometimes the steering wheel.The noise is coming through the rear of the vehicle. My son asked why it sounds like a bunch of bumblebees in the back. This is why I thought it was in the driveshaft. When I found out the previous owner had it in for warranty work due to the same problem, Ford technicians replaced the driveshaft. That apeased her until she brought it back in at 70,000 miles. They did nothing then. Whatever the problem is has been there for at least 70,000 miles (it has 110,000 now). That ruled out wheel bearings in my mind because it hasn't gotten worse. I am now leaking some ATF between the transfer case and transmission likely due to the vibrations. All of the bolts on the extension housing are tight. Transmission mount seems fine. I even loosened the motor mounts and retorqued. For that matter, I also loosened the tranny mount and used a large prybar to pick up on the transmission a few times and retorqued the mount. You can see why I am going nuts!

 

Bumblebees in the rear? I would take a different approach. I would take off the roof rack bars just for the heck of it. If you eliminate all the underside mechanical issues then it has to be something else. maybe something aerodynamic?

 

A couple of questions:

Does your Ex have the vibration damper on the transmission cross member?
Have the axles or limited slip ever been looked at?

 

Roof rack cross bars were taken off in the spring.
Both vibration dampeners are in place (transfer case one is bent slightly)
The internal diff parts appeared to be OK when I had it apart when I put the bearings in.
I really appreciate the feedback.

 

Can you remove the rear shaft and in 4wd get up to speed and see if the vibration is still there? May rule out some things. What is your driveshaft angle? (angle between driveshaft and pinion) have you played iwth shimming the rearend further nose up/down?

Did you ever solve the original vibration when you bought the truck? If so what did you do? Also the problem started after your lift?

Could teh axle housing be bent/warped? A bent axle shaft perhaps? Not sure if its too possible with full floating axles but with a weird prroblem anythings worth a look at this point.

 

1-
I never have resolved the original vibration. The vibration is the same with the F350 blocks as it was dead stock when I bought it. The driveshaft angle is within 2 degrees of pinion and transfer case. The X is quiet up to 50+ mph. I drove it for a week with the rear shaft out. I didnt have the vibrations I have with it in. There was some noise from the front axle, but seemed similar to any 4 wheel drive when locked in. I have noticed when I am coming down from speed and on the brakes, it has a louder rumble at 55-60 mph and shakes the brake pedal, seat, steering wheel, etc.
BTW- thats quite a stable of cars you have.

 

Did you check the ujoints in the driveshaft? That would cause your sensation you're feeling, and would be speed (not rpm) sensitive.

 

Thanks, I just wish I had more time to stay on top of em all! Working on putting the excursion up on some 38.5" baja claws with a 10" BDS lift right now. Really I shoulda bought a house instead of built all these freakin cars though!

As far as your truck though you definitely have something uncommon going on there. You pull the rear driveshaft and the vibration goes away, and new driveshaft's haven't helped. For some reason when theres a load on that diff something is out of balance. I would be looking at your diff, it's the only thing I can think of that would possibly act differently with a load going through it. Or possibly a slightly tweaked axle that makes the carrier move around, when the driveshafts moving things along it takes away some of the play in there and the vibration becomes more pronounced? I cant see it being a wheel bearing as its a full floating axle so theres never really a change in the load on that bearing when the driveshafts in or out. I'm kinda just thinking out loud here, sometimes you get enough people doing this something clicks. How did those carrier bearings look when they came out? Does the housing have any fluid leaks where the tubes go into the housing? Any evidence the housing may have hit something at some time?


Ever just price out a junkyard rear axle?

 

He's been through a few driveshafts, even had a fancy one with a CV built into it made up. I'd be pretty mad and beating things with driveshafts if I was in his position. He has way more patience than I do! lol

 

Sounds like a great front wheel drive excursion. :-)

 

With the rear wheels off the ground - is there any play in the wheels? Might still be bearing related even if it isn't getting worse over time. Has the emergency brake system been checked?

 

Mine had it bad. I did the CV shaft and added a 2 degree shim and it solved the problem perfectly. Good luck man, I feel your frustration.

 

.... sounds like my nearly stock '05.

Anything over 65mph and it's like a choir starts humming in my back seats. Then, at about 75.... might as well not talk, 80-85 you can change the pitch on the gas, or off.... and at 90+ it goes away.

I called Ford, since it's done it since new. Told'em about it, and he said bring it in. Never did... as it's not too often I'm up at 80+ .... so I slowed down a bit, and just live with it.

I just figured I can't have EVERYTHING. I still love my Ex.