Hello all. I have a vibration from the rear end of my ford E350 I cannot figure out. Started after having the Diff swapped. Comes on at 75ish MPH, and is a high frequency vibration. I have taken it to shops to have looked at and the shops have put it on a lift and gotten behind the wheel. They say that the wheels hop at high speeds during so, and that it is in the wheels ad tires. I had the wheels/tires "road force" balanced. I have torqued (very carefully) the wheels and tires. I put on new brakes and rotors.

Here is my setup and what got me here.
Ford E350 2013 with the V8 Passenger
2 inch lift in the front.
Bigger tires and BFG AT wheels. 2 inch wheels spacers rear
No seats in the back
No rear lift, just cargo springs with a trailer helper leaf setup.
Changed the Diff to a Yukon hosing with a 4.53(or whatever) from the factory 3.90. This exact change is when the vibration showed.

Things I have done.
Had the drive shaft checked.
Had the Diff checked twice
Had the tires road force Balanced.
Rotated the tires.
Changed the wheel spacers
Road Force Balanced wheels.

Observation. When I was double checking the torque on the spacers and tires last week, I noticed some play in the rear wheels and tires. Is this normal? I also really notice it when decelerating? Strange

 

"Play"? Rotational yes. Any other play is suspect and you should start taking things apart to find out if you have broken or worn parts.

 

Can you remove the spacers or put the factory spare on (if you have it) to see if it makes a difference?

Can you tell which side it's coming from? Maybe rotate the brake disc (sequentially) to see if you notice any improvement or degradation (check for disc out of balance)?

 

It's probably from the higher gear ratio. This puts more freeload on the U joints as their stress is lessened. The driveshaft is spinning faster too in relation to the axle speed. I got the same thing when I swapped from 3.55's to 4.10's in my van's 8.8 rear. It's starting point has moved up the MPH scale as the gear set has broken in. Used to start at around 75, now it doesn't start til after 80 mph. It too is noticeable when decelerating. There should be no movement in the wheels on the hub after tightening the lugs. I would run it a few thousand miles, then change the gear lube. When you drain it, check for metal in the oil. There may be some, just not a lot of it from the gear sets wearing in together.

 

Using my best internet troubleshooting skills...

Sounds like the diff was not set up right.
What does "Had the Diff checked twice" include?
Proper pinion preload check?
Wear pattern check?

Did the diff install get new bearings throughout? Maybe one is bad or not torqued right?

My limited experience with Dana 60s indicates the pinion bearing is a weakness.
Noticeable as a hum or rumble especially on decal when not set up right and setting them up right is not guesswork.

My pinion seal leaks and my pinion is grumbling on decal again but I don't have a vibration.
I think this semi-float 3.73 open D60 is going to get swapped for a full-float and a fresh set of 4.56 gears so I can tow my toy hauler (5.4 V8, 8000ish lb trailer, 500 mile minimum distances)