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OT - F350 Vibration

Antarctica

Hot Rolled
Joined
Jan 16, 2007
Location
Annapolis, Maryland
OK - Followup to the u-joint thread.

This is a new to me 2002 F350 7.3 Crew Cab Dually, manual shift (6 Speed), 4x4, dana 80 rear. This has a truck camper on it that will live there full time. Has a slight vibration at between 60-66 MPH. Per the other thread, I replaced the driveshaft u-joints and carrier bearing thinking they could possibly (though I didn't think likely) could be causing it. They probably needed to be done anyway.

Some additional details on the vibration:

1 - Kicks in just under 60 MPH and goes to about 65.
2 - The vibration is very faint. You can't really hear it, but you can feel it in your feet/seat.
3 - Important one here.. It is periodic. It is on for about a second, and then off for about a second. On a few occasions, I think I felt it at twice the rate (i.e., on half second off half second).
4 - While the front tires have uneven tread wear due to no rotation, it is independent of road surface
5 - It is independent of whether the engine is loading or dragging. Usually, I find that rear pinion bearings change sound depending on whether the the engine is driving or dragging, so I don't think its the pinion bearing. That said, when I got the truck, the rear end was two quarts low on fluid, and I think the pinion seal is probably leaking (I need to check it again after adding gear oil).

I'm not sure how to isolate the cause at this point, other than keep driving it and let it fail. Its not a big deal, but I definitely think something is on the way out. Problem is, I have a camper on the back and its always going to be driven far from home and with the whole famn-damily onboard.

I'm looking for ideas on how to determine the cause/source.

As always thanks in advance.

Brent

PS - Yes, I know I could post this on a truck forum, but I trust the expertise on this site a whole lot more than a bunch of dudes extolling the virtues of 6 inch vs 8 inch vertical stacks and seafoam...
 
I have an F-250 that did something very similar. I thought it was just a tire out of balance so I had that checked. It too was intermittent and that's what was so puzzling. Out of balance is out of balance. One day I noticed a slight smell when I got out of the truck. I put my hand on the hub caps and the front left was fairly hot. I changed out the caliper and the problem went away. Apparently it was sticking from time to time and causing the rotor to heat up. For some odd reason the warped rotor didn't start to vibrate until I hit about 55 mph. Just something to check.
 
When you had the driveshaft off, did you feel any play in the rear yoke checking full rotation for a spot on the ring gear that may have an issue?
Any sign of a ding or small dent, or a missing weight from the driveshaft?

Was chasing a vibration on a T100 a few years ago that I did the same, u joints, carrier, checked the outer rear wheel bearings and found a front tire with a torn belt/cord. But the truck does have 240k miles on it, so a little rattle was tolerated
Try swapping the front tires left to right and see if it makes any difference.


Mike
 
Gotta check everything... lots of things can be causing it. Those trucks normally lead a very rough life and are pretty beat. Tire balance, tire pressures, brakes, axle, driveshaft, transmission, etc etc etc. Does it have a driveshaft mounted parking brake? How rusty is it? What state are you in?
 
look up death wobble, that's exactly how mine started on my 06 f250 4x4, its probably a combination of things causing the front end to shake and started as a harmonic that eventually would shake the truck violently.
Start with new balancing and rotating the tires, or even new tires, then an alignment by a shop that knows what there doing on 4x4, not wal mart or other big name tire shop. Maybe even new tires. also make sure your inflating the tires to the tire pressure on your door.
Next is the shocks, the standard press down test doesn't work on a 3/4 ton 4x4. When I took mine off they were shot, ranchos btw original to the truck. everything improved it a little bit but the shocks is where I stopped, finally fixed the problem.
My brother on the other hand had to keep going and replaced the trac bar on the front end. To test it jack the front end up grab a good pry bar and try to get a wiggle in it or on the other front end components.

Other than that turning of the rotors may be in order.
 
I have a 2001 F350, if I worried about every vibration/clunk/wobble it does periodically I'd spend my life underneath it. Avoid driving at 60-65, that's what I would do.

I would imagine it's the tires. Change the tires before you try anything else.
 
i have owned, and used, a tire truer for many years. one particular model of vehicle i routinely serviced would always get a vibration between 55-65 unless the tires were trued first before balancing. it's not an expensive procedure

btw this same vehicle could not be balanced on a computer style balancer. i got perfect balance doing them static on the truer. i suspect yours is not that way tho'
 
You need to troubleshoot. Narrow it down. Could be anything.

I have owned a lot of superduties. They are tough, but they aren't a cushy ride. That truck has leaf front suspension identical to when Ford started using it under 4x4's in the 1950's.

I have had unit bearings both catastrophically fail and get sloppy causing weird stuff. Had a loose steering box on the frame. Had a loose pitman arm on the steering box. Had a truck that was wrecked real bad and repaired long ago and the passenger frame rail was bent up enough to touch the bottom of the cab floor. That would send strange vibrations through my feet every now and then. Had bent rear driveline sound like the rear end was going out. Had a loose rear axle nut make the truck handle strange (brakes worked fine). Had a ZF6 truck owned by an old guy with some disease that made him shake. His foot was constantly on/off/on/off the gas pedal. Over time it broke chunks out of the teeth in 6th gear.

I've had stick trucks with lots of miles develop vibrations from worn material building up inside the pressure plate. Had a couple dodges with 300K++ on them with original clutches do this. One I actually pulled it all apart, blew and scraped out the pressure plate, replaced the pilot bearing and put it back together. Drove perfect.

Exhaust is a common rub/vibrate thing to look at. Especially if intermittent. Does that 7.3 have an aftermarket downpipe? Might look to see if whomever installed it bashed the firewall enough for clearance.
 
- 181,000 miles, one owner truck (prior to me), used mostly to tow a 5th wheeler.
- Never was a work truck. In very good condition (interior looks like it's new).
- I put new front shocks on. Also did rear brakes and rotors when I got it. No driveshaft parking brake (the parking brake is on the hub, inside the rotor)
- Some rust, but not a lot. Has spent its life in Maryland.
- Does have a Banks 4 inch exhaust and a Banks Brake.
- Avoiding 60-65 is difficult!
- Vibration does not feel like it is anywhere in the front end. Feels like driveline if I had to guess..
- I believe it has had a clutch once in its life.
- Can't for the life of me see how a consistently periodic vibration that does not vary with road surface could be tires, but I've been wrong before.
- I could possibly see a caliper slightly dragging and going into and out of oscillation.
- the slow cyclic period does make me wonder about the tcase and tranny...
 

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The coming and going at a low rate frequently is caused by 2 vibrations. They are close in their frequencies but not quite the same and they form a beat frequency. The speed it's happening at is probably the wheel hop natural frequency. Strange that you are feeling it both in the seat and the steering wheel. If it were just the fronts or just the rears I'd say the pair is wheel hopping at slightly different frequencies. Balance or runout in the tires would be my guess if the shocks were changed.
 
One other thing I thought I would mention. I had a D100 Dodge pickup that I replaced the U joints on. I replaced the joints because of the clunk of taking up all the slop in the drive train. Somehow I got the drive shaft out of phase (or something) and it vibrated at highway speed. I knew it had to be the driveshaft because it was the only thing I worked on and it didn't have a problem before that. I dropped it and turned it 180 degrees. Vibration went away. Perhaps there is someone here that can explain that one.
 
I wonder if it would be at all insightful to run the truck at that speed on a drum type chassis dyno while observing from outside the truck? Since you're not doing dyno measurements maybe someone will cut you a deal. Similarly, maybe you could have another vehicle follow along on the highway next to your truck to pinpoint the origin.

BobM3 makes an excellent point about how two higher frequencies will combine to create a much lower frequency.
 
I would go get all the tires balanced, clean the hubs and the wheel surfaces really well and torque the wheels down evenly and see if it does the same thing. Its not a shaft mounted parking brake truck so you can rule that you. Crawl under and see if there is any play where the driveshaft meets the tcase. Front U joint can actually cause vibrations too, even in 2wd. I will just pull the front shaft and drive it to see if it makes a difference. Check the gear oil front and rear. Check the transmssion and tcase oil.

Also if everything else checks out I have had a driveshaft re balanced before and it did wonders.
 
Did it do it before the camper was put on? May be an aerodynamic thing.

Or, with all that weight back there....and even hangin out the back some ...
You may have changed the driveline angles.

Jesus that is
a big camper....there a truck in there somewhere ?

It looks like it's squatting pretty good.
 
Ladder bars to hold pinion angle.

Air bags for proper ride height.

Did you mark the DS before disassembly?

And assembly back the way it came apart? if not rebalance.
 








 
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