So I started to notice a vibration only when the truck is under power at about 65 plus MPH...


Now I already know I have a driver's side front wheel hub that needs replaced and the springs are typical Excursion springs (they all 4 need replaced), but this is the first time I have experienced the vibration.


Before you ask...the steering wheel does not vibrate. The vibrations can be felt at my feet and they create a low toned droning vibration that starts at about 65 mph.


When I'm cruising down the highway at 75 mph and take my foot of the accelerator, the noise and vibration basically goes away.


My diagnosis (and a few probably "stupid" questions): u-joints are going bad...


Any thoughts?


Could it possible be something else?


Any ideas how long they may last before I "have" to change them?


What is the worst thing that could happen if they completely fail?

 

Very similar to what I had going on or recently. The rear joint was bad but didn't look that bad until I took it apart. It was actually really bad.... Crawl under there with a big screwdriver driver and see if it wiggles.

 

This type of vibration sometimes can be caused by a bad COP.

Try this, when you're normally experiencing this vibration push the O/D or Tow/Haul button and see if the vibration goes away when your RPM goes up.

 

I believe the OP has a 6.0 PSD.

In fact, I noted very similar vibration right around 60-65 when towing heavy but no symptoms when not towing. I will be interested to see if this is the u-joint as it may be something I will have to address as well.

 

Also, inspect driveline to see if it threw a weight off.
When they're balanced, weights are used near ujoints.
Mine did this.

 

Bad u-joints? Driveshaft balanced as listed above? When I bought my EX they dealer had to get the ujoints replaced and shaft balanced due to a vibration that started right at 65 mph.

 

When this happened on my truck, one (and another time both) hubs didn't fully unlock from the last time I used 4wd. I had to get out, flip the lockout a few times, then manually turn the the ujoint to unlock it.

 

I have the same issue on my 2003 7.3 Excursion. I will be watching to see how you fix yours.

I had the u-joints replaced, and the drive shaft balanced. However, even with these fixes, I still get a very specific drone/ audible buzz right around the 80 MPH mark. If I release the fuel pedal, it goes away instantly, if I get back on the pedal and throttle the fuel up and down, I can make the noise happen on demand but only when I am right at 80 MPH.

The other factors I am working with, is that I have about an 8 inch lift in the rear (spring only, no blocks), newly rebuilt transmission with a stage 3 torque converter, and I am running stock 265/75R16 M/S Cooper Discover tires at 55 PSI that are new within the last month. Oh, and I have stock gears in the diffs, 3.73 with newly changed fluid with adding the friction modifier for my limited slip.

 

You have a 8" in the rear only & running 265/75 tires
The reason your doing 80MPH every time you look at the spedo is your standing on the skinny pedal !!

 

[QUO.TE=harley4jcs;15018573]You have a 8" in the rear only & running 265/75 tires
The reason your doing 80MPH every time you look at the spedo is your standing on the skinny pedal !! [/QUOTE]

I should have been more specific, I have a 6 inch Pro Comp lift, but change the rear springs out to get rid of the 4 inch block and it ended up being more like an 8 inch lift in the rear with about 2 inches of Rake.

 

Dealing with a very similar situation now as well. My issue is vibration that starts about 60 mph but is present under power and when off the gas. Haven't had a chance to remove rear driveshaft yet and check joints or get it balanced. I will be watching this thread as well...

 

I should add that the vibration went away after I completely unlocked the front end.

 

Interesting...not to sound crazy but could you post a picture of your rig with the lift and stock tires? There's a good chance that I'll end up having to run on stock rubber for a while, even after Monster gets a 4"-6" lift. I'm curious how it might look.

 

BIG hammers and BIG screw drivers...go BIG or go home, right? Seriously, this sounds like an easy enough test to help narrow it down to the U-Joints...I'll try it!

Monster is a 6.0, but this is easy enough that I'll give it a try...can't hurt any...

Pardon my possibly silly question...If not all shafts have been balanced, how would I be able to tell if it threw a weight?

Yikes! If my Warn hubs are stuck I'll be pissed and that probably accelerated the deterioration of the wheel hub.



Since money and time are huge factors right now, I'll try all of the above to see if I can definitively diagnose the problem.


Thanks for the ideas...


I'm a DIY driveway mechanic and with the days still so short, I rarely get home in time to have any daylight to work on her, so it'll take me awhile to scrape up the time, but I'll keep you all posted about what I find.

 

Update:


1. Wheel locks are free and smooth. The axles move freely when not locked in 4x4.
2. As suspected the "Tow/Haul" mode did not make any difference.