truck shakes between 70 and 80 mph - Diesel Forum -
'99 & up 7.3L Power Stroke Engine and Drivetrain Discussion of the '99 & up 7.3L Power Stroke diesel engine and drivetrain in the 1999-Up Super Duty trucks and Excursions. No gas engine discussion allowed except on transmissions and drivetrain that pertain to all models. Please confine discussion of topics in this forum to those items that are specific to the 7.3L Power Stroke engine.

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post #1 of 5 (permalink) Old 09-22-2010, 05:40 PM Thread Starter
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truck shakes between 70 and 80 mph

Highway driving, my 2001 excursion, 140k miles, has developed a shake around 75 mph. Slow to below 70, speed up above 80, and it goes away.

Tires are michelin with ~15,000 miles on them. Had them balanced and rotated front-to-back last week, problem unchanged.

Any suggestions?
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post #2 of 5 (permalink) Old 09-22-2010, 08:02 PM
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Is the shake coming from the front or back? Left or right? I thinks it is still your tires. Try having a different shop balance them.

Another trick I heard was using two acorn style lug nuts to perfectly center the tire on the hub. You then install the six factory lug nuts and remove the two acorn nuts and replace them with the remaining lug nuts. I havent tried it though.

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post #3 of 5 (permalink) Old 09-22-2010, 09:13 PM
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Originally Posted by lone_star_dsl View Post
Another trick I heard was using two acorn style lug nuts to perfectly center the tire on the hub. You then install the six factory lug nuts and remove the two acorn nuts and replace them with the remaining lug nuts. I havent tried it though.
Not sure how that would work, my tires sit pretty tight on the hub...

My truck had a shake at those speeds for two reasons (two separate times), one was a bad front balljoint, the other time was the carrier bearing.

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post #4 of 5 (permalink) Old 09-22-2010, 10:50 PM
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If its coming from rear, Ujoints. If its all the way around bad balance job. They make an adapter plate for 8 lugs wheels for balancing. With out youll be there all day trying to balance them. And they should be dynamic balance. That means wheel weights on the outside of the rim and the inside of the rim. You DO NOT want a static balance.

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post #5 of 5 (permalink) Old 09-23-2010, 05:50 AM
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It sounds like tire to me. I would ask the tire shop when was the last time they calibrated the wheel balancer. If the machine is out of spec than your wheel/tire assemblies will be out of balance. I would also have them check the "Road Force", aka radial first harmonic. These forces appear on all tires but the frequency and severity depend on the tire itself. I would have the tire shop rebalance after a calibration of the machine, check the "Road Force" of the tires. Once the tires are complete have the tire with the lowest "Road Force" placed at the left front, the next lowest on the right front and then the tire with the highest at the right rear.
Depending on where you get your tire work done the balance is free and the "Road Force" is a nominal charge. If the tire shop is any good they are calibrating their machine a couple times a week since it only takes 5 minutes to calibrate.
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