2002 Sport Trac with annoying vibration

[cpman]

Right at 45 mph (+/- 3 mph) my 2002 Sport Trac (4:10 gears) has what seems to be a continuous drivetrain vibration. Other than that, up to 85mph no vibration. Ironically, 45 mph is what most of the posted speed limits are, so that's were I drive most of the time. Checked tire balance, transfer case to rear diff angles and u-joints. All seems good. I did not remove the drive shaft to check u-joints, so it could be possible that I could have a tight u-joint (100k on the meter, original u-joints), but you would think it would vibe all the time if that was the case.

Has anyone else here chased this problem, and if so how was it resolved? Possible balance issue? I love this truck other than this issue that I wish I could fix, then it would be perfect.

Any opinions would be greatly appreciated.

 

[swshawaii]

Found a TSB that applies to 4x4 only @ 55-75 MPH. Hopefully not the issue, new drive shafts aren't cheap. GL

http://www.revbase.com/BBBMOTOR/TSb/DownloadPdf?id=129316

 

[roughrider17]

Had the same problem on my 02 ST, jacked it up to check my tires and see if there was any abnormal wear and noticed an ice chunk easily 1 foot in length jumping around behind the rubber wheel well. Once i removed it, the vibrations stopped. Not sure if this is the same problem, but its worth a shot.

 

[05dakotatrac]

Given your location it's a good chance snow and ice packing in the wheels. If not that I would lift the front end and give her the shake down have someone help shake the wheel side to side and up and down and look for play in the ball joints wheel bearing and tie rods inner and outer

 

[Galactica]

It could also be lugging in 5th gear OD with the TC locked up and you are getting engine vibration through the drivetrain.

 

[charthouse]

annoying vibration

I chased a very similar problem on my '04.. did similar checks on driveline, u-joints replaced, wheel rotation, balanced etc.... vibration goes away over 50mph.. recently purchased new all seasons (Yokohamas) and vibration is gone.. appears broken belt or something in older tire.
if your tires are recent, try swapping wheels for a day with someone else's same tire size. worth a shot!