I have an 03 6.0 Excursion. I've not felt really any vibration difference with the hubs locked or unlocked. Driving speeds from idle to 80 on the interstate.
If the hubs are unlocked the front driveline shouldn't be turning. If it is, It definitely isn't spinning at the same speed as if it were locked. I've recently replaced everything in the front axle. Timken unit bearings, Spicer U-Joints and all the seals,including the vacuum seals and other than everything working properly, there is no difference in vibration. The only thing left to replace is the tie rod and drag link and everything but the axle shafts, housing, nuckles and gears have been replaced.
Once you get the vibration sorted out, if you then find yourself chasing a clunk, make sure to replace the Sway Bar End Links, Track Bar Bracket Bushings and Steering Stabilizer shock. I replaced the ball joints with XRF (highly recommended) along with the other listed items, and still had a clunk when hitting bumps and a creak when turning. The clunk was the track bar bushings and the creak was the stabilizer shock.
So at this point I've replaced on the front axle:
Brake pads
Brake rotors
Both unit hubs
Ball joints
All seals inside hub for ESOF
Vacuum seals
Axle shaft (knuckle) u-joints
Sway Bar End Linkes (look like a dog bone)
Sway Bar (track Bar) Bracket Bushings, these are on the back side of the axle under the u shaped hold downs
Steering Stabilizer Shock
Shocks with Bilstein
Everything is nice and tight and quiet. Once I replace the tie rod, drag link and ends it should drive better than new. Now there is between a quarter and half inch of play in the wheel and 90% of that is wear in the drag link to tie rod joint. Truck has 169,000 miles and the steering linkages are the factory ones.....
