2003 F150 unknown vibration

Joined
Oct 4, 2009
Messages
770
Location
Litchfield, Ohio
Trying to help a good friend of mine with his truck. Its a 2003 F150 4x4. The truck has a vibration that is very noticeable between 40 and 60 mph. The vibration isn't consistent in occurrence or frequency. Its hard to even tell where its coming from because its not a super strong vibration but its enough to notice. He has had it to two mechanics both of which said they couldn't feel it. This has been going on for at least 4 years now with his truck. At the time it started the truck was his daily driver but its only a backup now. Truck only has 120,000 miles on it. He put new tires on it thinking they were the issue. Didn't help at all. Had the wheels re balanced thinking they were out but that wasn't it. Everything in the front end is tight. No play in the steering or wheel bearings or ball joints. We replaced all the shocks thinking maybe one was bad but that made no difference. Replaced the universal joints in the driveshaft thinking one was bad and still no difference. I'm at a loss as to what it could be.
 
A couple of things to check.

1. drive shaft splines. Ford makes a PTFE grease for them. Dry they also clunk when starting and stopping.
2. Spark plugs. Can cause shakes at different speeds when the gap gets too big. Often mistaken for torque converter shudder.
3. Transmission fluid. Worn, wet or tired fluid can cause issues.
 
Before any further replacement of good parts, where is the vibration felt? Steering wheel or seat? That atleast will give you some direction to find the source of the vibration as far as front or back. Does it occur in one gear? Engine under load? Myself, I would diagnose before making the parts guy rich.
 
Before any further replacement of good parts, where is the vibration felt? Steering wheel or seat? That atleast will give you some direction to find the source of the vibration as far as front or back. Does it occur in one gear? Engine under load? Myself, I would diagnose before making the parts guy rich.
That's the biggest problem is telling where its coming from. Its really not that strong of a vibration. It does it when accelerating or when coasting.
 
Many things could be wrong, including something as simple as "U" joints, engine/transmission mounts, or as complex as internal transmission wear or engine misfires. This we know.

What's not so clear is when a system as complex as a drivetrain has resonant characteristics that show up only at certain speeds. These are exceptionally hard/impossible for the average person to deal with. Many of us have noticed large weights hanging off of transmission tailshafts or differentials. These are put there to damp such problems out. It could be that such a thing was removed... Or needed.


ford_8_8_w_damper_weight_7073e68681b55d607aa16e633c026fddda5e8691.jpg


DSC00160__80681.1575825703.1280.1280.JPG
 
Another vote and +1 for possible U-joint issue.

Just reach up to the front and rear of the shaft (the truck may be tall enough to just slide under)

Grab the shaft at each end and watch the joint trunions (cross parts with the bearing caps) and give them a twist, shake up and down, pry a little with an ugly screwdriver. Any clicks, clunks, or free play at either end (tranny/transfer case and rear differential yoke/front yoke and x-fer case output)...swap em!

Just did mine for a moooooooaaaan @ slightly above legal highway speeds. Both the rear shaft at yoke to diff and the spline-side forward output shaft from X-fer case were loose, revealed when giving them a tweak with ugly-driver.

Changed all 4 joints with Spicer components for just under $97. I had to heat and beat them out with a ball joint tool due to factory injected Nylon holding the caps in the yoke ears, but totally a driveway and afternoon job. Took longer to detention them with light thumps from my stubby sledge hammer. (Don't install them if they're tight, tap-a-bump them a bit after clipping them together and pressing the bearing caps in. They should be as loose as a goose before you bolt them up)

20210417_122623.jpg
 
That's the biggest problem is telling where its coming from. Its really not that strong of a vibration. It does it when accelerating or when coasting.
From that, I would be looking at motor mounts or driveline.
 
Back
Top