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Discussion Starter #1
Morning All!

I consider myself a pretty decent wrench but have something strange going on that me and a couple of other full time mechanics have never seen. Need some help, thoughts, ideas from the experts!

Truck is a '00, 2 wheel drive, Supercab, 7.3, one owner (me) with 148k on the clock. Truck doesn't get drove much, maybe 1~2k a year, but when I need her, I need her. Truck has never been in any shop except for tires and front end inspection. I have done all work myself so I know it's done correctly. (trust issues with my vehicles)

Background: Tires, wheels, U-joints, center carrier bearing, all replaced about 4k ago. At the same time, the entire brake system was replaced EXCEPT hard lines, master cylinder and ABS pump. Speaking of which, this truck has 4 wheel ABS. During brake system rebuild, all front wheel bearings, seals and such were replaced. All parts were high quality, Spicer, Moog, Motorcraft. Brake parts were all Power Stop with slotted and drilled rotors all around. At this time, front end was inspected and the only other part with wear was the sway bar bushings. Those and the end links were replaced also.

Now the problem: Started last Wednesday, on the way to hardware store all was normal. When I started the trip home, started feeling a vibration at about 45 mph. When I slowed for a turn, vibration continued but felt like more of a pulsing than a vibration, even without brake applied. Continued toward home and when I went to slow down for turn into the road I live on (55 mph to 0), truck almost went into the dreaded Ford Death Wobble (very familiar with this!). Driving slowly down the road home, 15-20 mph, it almost felt like a seriously warped rim or someone pulsing the brakes. The slower I drove, the more pronounced it was. No noise, nothing else different. Hmmm, I have to check this thing out....

Fast forward to Saturday morning. Took truck out and around the block, almost 10 miles where I live. No evidence of any vibration, pulling or anything out of the normal. Get truck in my shop and check tire pressure, all good. Jack up front end, everything rolls smoothly, no calipers dragging, no unusual loose motion anywhere I can tell. Ok, I'll drive it this afternoon on errands...

Drove close to 60 miles Saturday afternoon, on road, in town, speeds from 15 to 70 mph without one hint of an unusual vibration. Then, I'm heading home from my last stop, traveling at about 60 mph, had to slow for a car, did not apply brakes but when speed dropped thru the 45 mark, vibration started back and continued the 15 mile trip home. Vibration would diminish a little at around 50 and would get worse as I slowed. Same thing, at real slow speeds, felt like brakes pulsing or something trying to bind up then release. Made it home and parked, scratching my head.

Got up Sunday morning and thought "what the he!!" drove the truck to breakfast, about 25 miles RT and not one ounce of vibration anywhere!

I should mention when it starts this, it seems like the front end wants to pull left. However, our roads around here are so screwed up, it's hard to tell!

Thoughts, Ideas, Suggestions??? I have a good front end shop and plan to take it to them the first opening they have. Still not convinced it's in the front end though. Is there any way the ABS unit could cause this behavior?

Thanks in advance!
 

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I would say you have something bad in the steering system, you just missed it (tie rod end or ball joint). So I would recheck that first and have a second or third set of eyes on it. Pull the front tires and recheck the hubs (new ones will fail sometimes) If all that is good look for Zebras (not all hoofbeats sounds are horses). Check the lug nuts, had a similar issue with intermittent vibration on my Ford Ranger. It was winter and I figured it was just snow/ice buildup on a tire, once I saw the front tire head into the ditch I figured out the problem!! I was the one that put it on so stood in the corner and yelled at myself for a while. If the lug nuts are good I would look at the driveshaft and rear axle spring attachment points. Check each of the U-joints carefully and if you have a sliding driveshaft spline make sure it is free. Does not sound like a brake system issue to me at all but make sure front calipers slide pins are free. Keep looking you will find it!! It is always a major pain when you get an intermittent issue like this. Let us know how it turns out.
DENNY
 

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From a vibration analysis standpoint the symptoms you describe are classic mechanical looseness symptoms as a source force feeding a part or system at a resonant frequency, resultant amplitude multiplication of the source. A scenario very close to what excites "Death Wobble" a term I find inaccurate. Have you checked your wheel lugs for torque and tires for missing balancing weights and crossbar clamp?
 

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I'd jack it up, put it on jack stands, take the front wheels off, and check all of the nuts and bolts behind there to see if maybe some nuts or bolts are coming loose, or maybe weren't torqued correctly.
 

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Discussion Starter #5
Thanks all, yes I have checked and torqued all lug nuts. Got under the front end yesterday and checked every nut and bolt I could get to with it up on jack stands. Haven't checked anything on the rear except for the u-joints and center bearing. Think my best bet is taking it to the shop where they can get it up on a lift and thoroughly check everything. I totally agree, it seems like something is loose, somewhere.

Thanks again for the suggestions!
 

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Discussion Starter #6
Ok folks, maybe it's solved. Right front tie rod was worn out and alignment was off. That's all the shop could find.

So far, so good, only time will tell.
 

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GREAT NEWS!! Thanks for the feedback.
DENNY
 
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