Evidently I need to have a front end alignment (even though I just had one last month), as the front end of my truck has developed a significant vibration. My question is: Why does it only vibrate when the speed gets up to a certain range (roughly 35-40 mph). Before that speed is attained, no vibration. After that, no vibration. What gives?
I should think you would need to get your wheels balanced.
The vibration at that specific speed is probably due to resonance.
Have you hit any curbs lately? If you have a bubble in the sidewall, that could account for the vibration at certain speeds.
Count me in with xash, sounds like a tire balancing issue. One of the weights used to balance the wheel may have fallen off. Any small garage should be able to balance the front tires quickly and cheaply.
Vibration is not a typical symptom of misalignment. It is a typical symptom of tire imbalance and/or tire defect/damage. It can also be a symptom of loose steering or suspension parts, but those items should have been checked before the alignment. So in this case, it’s almost certainly a tire problem.
Most commonly tire imbalance shows up as vibration right around 60 mph, even going away at higher speed. My understanding is that this has to do with harmonics, though I can’t offer a detailed explanation. With vibration at 35-40 mph, I wouldn’t rule out imbalance, but I’d very carefully check the tires for any sign of damage or internal separation.
I had the exact same problem pnnlr, except mine was at 50-55. The problem was later discovered after about 2 balances, rotations, and allignments. Turns out, the rims on the car just didn’t fit or work properly, so I had to put the originals back on. After this I had little if any vibration. Don’t waste your money on allignments, take it to a tire place where they will allow you to return the rims you purchase if those turn out NOT to be the problem. GOod Luck.
Hmmm…brand new tires, and the weights are all on, and they were just installed last month when I had the alignment done. The rims are a non-issue, as they’re standard that came with the truck.
I go along with the tire balancing. It could also be a bad bearing tho.
Are your tires dirty? I recently had ice (in the winter) built up on one inner side of a tire. Everytime I reached 100 kph I felt my car shake.
I’d imagine mud would cause the same thing.
A tire could be out of balance, either by picking up debris, as badmana mentioned, or a weight falling off. There are often weights on the inside of the rim, where you wouldn’t normally see them. But usually tire imabalance doesn’t come on at 35-40 mph.
A tire could be damaged or defective, even if relatively new. But usually that would show up at lower speeds.
When loose steering parts cause vibration, it usually gets worse with increasing speed.
So this doesn’t fit the most typical symptom patterns. Still, it’s just about gotta be one of those.
I see from a Ford truck-related web site that there’s a TSB out re: vibration related to the rear portion of the drive train.
Anyone want to buy a Ford 150 pick up truck with 136,000 miles. It runs great (well, except for this vibration…)?
Resonance, in layperson’s terms:
The off-centre mass in the tire can be imagined as a pendulum. Left to its own devices after an initial push, it’ll swing back and forth at some frequency. If you give it a push at the right time each swing, it’ll swing higher each time – much like pushing someone on a swing. If you push at the wrong time you’ll probably damp out the swinging. The natural swinging frequency of the pendulum is called the harmonic frequency.
Like the pendulum, the off-centre mass in the tire has a harmonic frequency. Driving at certain speeds will cause the wheel to rotate at a frequency close to the harmonic frequency, causing a resonant vibration. At other speeds the resonance does not occur because the harmonic frequency is not reinforced.
Given the diameter of the tire and the speed at which the vibration occurs, you could calculate what weight (at what radius) is causing the vibration. I’m trying to think how that would help, though… probably better to see a mechanic than a mathematician at this point.
plnnr, Do you have a link to that Bulletin? I’ve got a 97 Exploder that has me banging my head against a wall. I’ve replaced the rear axles, pinion gear and seal, and all 4 rotors/brakes (well, I knew that wasn’t really related, but it was only 5 bucks less to get them turned) and tires. Still a slight vibration. My wife is like the princess and the pea in that damn truck.
I wouldn’t expect that to be perceived as a front end vibration. I assumed (yeah, I know) that you had a steering wheel wiggle or some other indicator that it was clearly from the front.
Now, if it’s possible the vibration is originating in the drivetrain, there are other likely suspects. The first thing that comes to mind are universal joints. The next is the driveshaft–it could have picked up something (e.g. a plastic bag got wrapped around it) or, if it’s aluminum, it may have been dinged by a pebble. And of course, the TSB should be checked out.
When I buy them I have to pay for balancing…Say, did you get them balanced? If so, it wouldn’t be that cause you can see the vibration on the balancing machine.
Another rare thing that can cause it is loose lug nuts.
I just replaced a tire that had a “broken belt” in it (so they said) that ended up with vibration modes at about 65-70 mph. So tire damage can do it. However, in my case the vibration was accompanied by a “thumping”, as if there was something stuck on the wheel and hitting the pavement every revolution - this thumping was heard at all speeds, and the vibration only came about at another speed.
On the theory that this is one tire that is out of balance or defective try swapping a front tire, one at a time, with the spare or one of the rear tires. Does the problem go away?
While you have the car jacked up, lightly run your hand all the way around the outside of the tire to feel if there are any local high spots. If so, tire is defective. But look at the tire first in case there may be a piece of glass embedded in the tread.
In addition to looking for missing weights, see if any appear to have been moved. If they were slopy when doing the wheel alignment they may have moved or knocked weights off. Don’t forget to examine both sides of wheel for weights.
For whoever asked for the TSB reference:
Resonance/Vibration reference TSB 97-15-24
2000-2500rpm resonance can be fixed by inspecting/tightening exhaust hangars, Engine Mounts & trans mounts and ensure proper alignment. If that doesn’t fix it the dealer will order and install dampners P/N Identified in TSB 97-15-24. (They must have had these problems before the SD era)
Shudder in Driveline
Reference Oasis Database #'s 11844 & 11845
Trucks that shudder under moderate to hard acceleration (towing) may be due to large drive line angle. This condition is normal and NOT detrimental to the operation of the truck - but improvements can be made.
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Check center bearing support bracket to make sure it is the right bracket PN 4831
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check to see if it is perpendicular to the “drive line” and it should not be twisted or cocked to one side - not aligned necessarily perpendicular to the truck frame. etc
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If customer uses vehicle loaded for less thatn 50% of the time. Shim center bearing down using P/N EOTZ-4A209-A to lower .75"
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If unacceptable level of shudder is still present & the vehicl is a XL 4X2 142/156/158 WB or XL 4X4 156/158 WB Model Replace Drive Shaft with one specified for the same application XLT model.
I hope this eases some of your concerns - I know it does mine. It looks like a design issue - something that can be worked and according to Ford Corporate not a servicability issue.
Universal joints says the doctor. Owner and truck are doing fine.