The truck is a 1997 F350 7.3 Crew Cab Dually. Today on my way home, it started feeling like a tire was out of round all of the sudden, like driving on a wash board. It quickly became worse, (within a mile) and as I slowed and was pulling over it became much worse, very violent kind of a bucking feeling.
I stopped, leaving the engine running, got out and was checking the tires, (which appear to be fine), and heard a backfire but the freeway was pretty busy, and I can't be positive the backfire came from my truck. Decided to limp the truck to the offramp and it seemed to be ok while doing this, but I was going pretty slow. Stopped again off the freeway, again leaving it running, checked under the hood and all seemed fine. Drove home, taking it easy around 45 to 50 and it seems to run fine now. The fuel gauge showed just a needles width below 1/4 of a tank. I filled the tank (rear) and it took 11.6 gallons, the manual says it holds 19 gallons, so I wasn't low on fuel.

Any thoughts on what may have happened???

Check your carrier bearing underneath.

Ok. But wouldn't that cause the problem consistently?

The carrier bearing feels very solid, in fact I think I remember the guy I bought the truck from telling me he just had it replaced. The U-joints look good also.

Any other suggestions?

Low fuel level is just inviting fuel related issues. My first guess would be injector misfires from fuel contamination.

But he still had 7-8 gallons in the tank vince?

Has the truck done it since? Is it possible you picked something up on the tires or something?

Was the steering wheel shaking as well??

Truckin4life said:

But he still had 7-8 gallons in the tank vince?

Has the truck done it since? Is it possible you picked something up on the tires or something?

Was the steering wheel shaking as well??

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Theres a valve a couple of inches above the screen on the pickup. If this valve is opened due to the screen being clogged, it will start sucking air (especially if the level is low).

It hasn't done it since, but I haven't duplicated the same conditions, (speed, load mainly). Where is this valve you mentioned located? Are there any in line filters I can check. Sorry for my ignorance but this is my first diesel, and I have only owned it about 6 months.

mnccnm said:

It hasn't done it since, but I haven't duplicated the same conditions, (speed, load mainly). Where is this valve you mentioned located? Are there any in line filters I can check. Sorry for my ignorance but this is my first diesel, and I have only owned it about 6 months.

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The valve is on the fuel tank sending unit. You'll need to remove it from the inside of the tank.

What opens this valve? Isn't there a point in the fuel line where I can check for water/dirt?

mnccnm said:

What opens this valve?

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It opens when the pickup screen gets clogged. It can also pop out completely, where the fuel goes straight through (not through a screen)

mnccnm said:

Isn't there a point in the fuel line where I can check for water/dirt?

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Its up on top of the motor at the rear of the fuel filter housing.

Turns out this was a blown tire on the rear inside drivers side. The tread separated, (the vibration), then blew, (the backfire). Guess I didn't check the tires good enough, must have been parked on the blowout. The good news is I know what happened, the bad news is it cost darn near a grand.