I just had 4 new Michelin LTX2's mounted on stock rims to my stock truck. They were balanced with John Bean equipment (high quality stuff). The diagnostics showed two of the rims a little of spec but not out of round and both well within tolerances. They all balanced up fine.

Previously, I had snow tires mounted on the same rims and they were were relatively vibration free ... for snow tires. I've only really driven the truck 1,000 miles home after I bought it so I don't have a really good "feel" for it but on the drive home, I had with no complaints and didn't feel any obvious vibrations. However, I was cruising around 65 mph for 14 hours and didn't do any sustained driving at 55mph.

The Problem: At 90 kph (55 mph), there is a distinct sounding and feeling vibration in the seat of the pants ... not in the steering wheel. It is not the death wobble and it does go away below 50 mph and above 60 mph. It seems to be coming from the rear.

Thinking the wheels were incorrectly balanced, I rotated them front to back. Exactly the same symptoms in the rear, no vibration transference to the front so I'm thinking it's not the new tires, old rims or balancing job.

I talked to the mechanic and he said the new LTX tires may have smoothed out the ride enough over the older, snow tires that now I feel what may have always been there but was less noticeable previously. He suggests it could be the drive shaft angle (sagging rear springs), an unbalanced rear drive shaft or perhaps u-joints.

Before I take it back into the shop and start spending a ton of dough to figure and fix, I'd like to have your opinions as to what you think it could be, what they should look at in sequence and anything else you can think of that may be useful for me to know.

Also, if they start to take it apart, what might I have they do while it is apart (maintenance or replacement wise) since I'm paying the labor to have it "opened up" anyway.

Thanks.

 

There are a couple TSB's on that. On the 2 piece driveshaft you shim the carrier bearing down. On the one piece you swap the tapered blocks side to side.

Swapping the tapered blocks worked on mine.

Josh

 

Thanmks a bunch Josh. Where do I access the Technical Service Bulletins? I've never had to go look for one before. ~ Bug jr ~

 

Here is 2 Piece:
--------------------------------------------------------------------------------

Tsb 07-5-11 Vibration/hop At 40-48 Mph - (8.0 Hz) - Trailer Hitch Equipped Vehicles Only
FORD:
2005-2007 F-Super Duty


ISSUE:

Some 2005-2007 F-Super Duty vehicles with a long wheelbase of 156", 158", or 172" (396, 401, or 437 cm) and equipped with a trailer hitch may exhibit a vehicle vertical vibration, often described as "hopping", on smooth or coarse road surfaces in the 42-48 MPH (68-77 Km/h) speed range. Although this behavior is considered normal for an over 8500 GVW truck, some customers may be sensitive to the concern.
ACTION:

To improve the 42-48 MPH (68-77 Km/h) vertical vibration, follow the instruction sheet included in the Damper Service Kit.

NOTE: THE INSTALLATION OF THIS DAMPER WILL NOT IMPROVE RIDE ON SEGMENTED CONCRETE HIGHWAYS, STEERING WHEEL VIBRATION/SHIMMY, OR GENERAL HARSH RIDE CONCERNS.


PART NUMBER PART NAME
5C3Z-5D008-A Damper Service Kit

WARRANTY STATUS:

Eligible Under Provisions Of New Vehicle Limited Warranty Coverage
IMPORTANT: Warranty coverage limits/policies are not altered by a TSB. Warranty coverage limits are determined by the identified causal part.
OPERATION DESCRIPTION TIME
070511A 2005-2007 F-Super Duty With Trailer Hitch: Install The Damper Service Kit. 0.6 Hr.



This has effected all Super Dutys from 2005-2014

 

On edit,'I see that deals with different shocks... I need to find the TSB about the shim kit for the carrier

Josh

 

I see this TSB is for the 2005-2007 years equipped with a hitch. I do have a hitch but mine is a 2001 model.

Also, mine doesn't hop ... at least I don't think it does ... unless they are attributing the vibration to a hop ... like an unbalanced wheel.

I'm thinking it's a different issue than what is addressed in the TSB?

 

I have a 2011 F250 Crew FX4. At 40,000 miles had a set of Cooper Discoverer AT3's put on and shortly after it wasn't a vibration that showed up but right at 50 mph feels like a thump or a tire out of balance. Like previously stated nothing in the steering wheel so I thought it was a rear tire out of balance. Took it back and had rears rebalanced and the same thing. Took it back again and the mechanic block it up under the axles, took the rear wheels off and ran it at 50 mph and if you put your hand on the rear bumper and you could still feel it. He felt it could possibly a brake issue, a u-joint, or even a wheel bearing. Took it to the dealer and had the brake pads replaced and the rotors turned. They checked the u-joints and they were fine. The tires were rotated so if it was a rear tire issue that would have fixed it. At 50 mph it still has that same thump or bounce and nothing coming through the steering wheel. Same thing or something different?

Thanks,
Jim

 

This refers to take-off etc... but has applied to the mystical 45-50 mph phenomenon as well:

06-23-4 DRIVE-AWAY SHUDDER OR VIBRATION

Publication Date: November 3, 2006

FORD: 1999-2007 F-Super Duty


This article supersedes TSB 05-17-6 to update the vehicle model years.

ISSUE:
Some 1999-2007 F-Super Duty vehicles may exhibit excessive drive-away shudder or vibration, under moderate to heavy acceleration from a stop. This may be due to driveline angle.

ACTION:
Shim the center carrier bracket downward to correct the condition. Refer to the following Service Procedure.

SERVICE PROCEDURE

When shimming the center carrier bracket, a maximum of three (3) 1/4" shims may be used (EOTZ-4A209-A). When refastening the carrier bracket use bolt (56564-S2). A 7/16 x 14 grade 5 bolt may be substituted providing that it extends at least three (3) threads past the nut. Use Motorcraft® Threadlock 262, and torque bolts to 46 lb-ft (62 N-m).

NOTE: IF THE VEHICLE IS NORMALLY LOADED, ROAD TESTS WILL NEED TO BE PERFORMED WITH THE VEHICLE LOADED.



Before beginning the repair, road test the vehicle to gain a feel for the harshness of the shudder/vibration.
Install one (1) shim, (DO NOT use threadlock on the bolts at this point), re-road test vehicle.
If condition is corrected, apply threadlock and torque bolts as directed above.
If condition is not corrected, re-perform step 2 (to a maximum of three (3) shims) and reevaluate vehicle.
NOTE: IF THE CONDITION IS STILL NOT CORRECTED AFTER INSTALLING A MAXIMUM OF THREE (3) SHIMS, REFER TO WORKSHOP MANUAL SECTION 205-00 FOR FURTHER DIAGNOSTICS.




PART NUMBER PART NAME
EOTZ-4A209-A Shim
56564-S2 Bolt
TA-26 Motorcraft® Threadlock 262

 

Were your tires static balanced or dynamic balanced? Road-force balanced?

 

If you get new tires and then notice a vibration, chances are pretty high that the tires are the cause.

 

Definitely dynamic balancing. I was standing there while they did the work. It is a pretty sophisticated system. The diagnostic phase involved laser scanning of the tire's wear patterns, road profile etc. I don't know about the road force question ... not familiar with that.

 

I know where you're coming from and normally I would say the same thing. However, given the advanced balancing technology they use (John Bean equipment), I would say the tires are not the issue. Plus, since the tires were rotated front to back and the symptoms remained the same, it appears the problem is with something other the tires.

 

Are there any other references that you know of pertaining to the same problem occurring at that magical 55 mph point?

 

There are 4:

Change the rear shocks
Shim the carrier bearing
Swap tapered blocks side to side
Shim rear axle 1-3 degrees

And the official one from Ford it seems... Learn to live with it.

The 05-07 and 11+ are the most effected. 08-10 seem to behave better on the highway.

There is a thread on .ORG over 40 pages long where Ford replaced a guys axle, springs, blocks, driveshaft and more and Ford finally said enough, live with it.

Josh

 

Find a shop with a Hunter Road Force Balancer. Have the tires rebalanced. Do not waste your money on any new parts.