I’m going crazy trying to figure out what’s causing the highway vibration in my Ranger! Here’s the deal: I’ve tried rotating, balancing, and and replacing, and the truck still vibrates a good amount at 60-65, and to a lesser extent as slower/faster speeds. It seems to be worse on the passenger side, since I can see the seat shake, but this may just be because my weight in the driver’s seat. In short, I’ve exhausted the tire route. I took it in to a transmission shop to see if the driveshaft needed balanced, and they said it looked fine. Here’s what’s interesting though: when they had the truck on the rack, and the tires moving (RWD), both wheels noticeable shook–I brought it to a Firestone, who said the rear axle was bent, but I don’t think that’s the case and it’s pretty much totally absent at high speeds. Any idea what would cause tire wobble like this?
Vibrates a good amount at 60-65… pretty much absent at high speeds
which one is it?
A bent axle shaft is a possibility
Firestone has diagnosed the problem, get it fixed before you do more damage. Once the axle is out you will be able to confirm it’s bent.
It really is both. 70+ and it smooths out, but still noticeable.
Would a bent axle be more/less severe at a specific speed though?
A slightly bent axle could create a vibration at one speed but not at another. Like a kid jumping on a trampoline, if they jump at the right rhythm they’ll really go high, but if they jump at the wrong rhythm they’ll quickly come to a stop. In any event, if the axle is bent, that has to be addressed first, before considering other things. If you question the accuracy of their diagnosis, have the axle assessed for true elsewhere.
Does your ranger use a carrier bearing for supporting the driveshaft midway? If so that part being bad or not adjusted properly is a common reason for vibrations.
Yeah… Unless I actually know the guy at Firestone and know that he knows what he’s talking about, I’m not gonna take as-read any diagnosis from those guys.
OP definitely should get it fixed, but it should be diagnosed at a place that does not hire high school kids and let them touch customer cars.
The principle is resonance. While the vibration is always there, the chassis reacts differently to the frequency (speed) of the vibration - and it appears to be worse in certain speed ranges. Google “Wheel Hop Frequency” and see if that doesn’t explain things.
Simple enough- put the truck on the rack and use a dial indicator to measure wheel run-out and wobble. If excessive, swap in a front wheel and re-check to rule out the wheel being bent. If it’s got run-out and not the wheel…
I had a pesky issue like this once. Turned out to be a tire. Looked fine otherwise but rotating at speed while suspended off the ground, you could easily see the eccentric runout causing the vibration…
Thornback: I took it to Firestone as a second opinion on the tires, and while I don’t have any issues with them personally, I consider them predominantly a tire shop, so I’m leery of their opinion on drivetrain issues. Thanks for the feedback so far though everyone!
I’m a little confused as to what route to take if it is indeed the rear axle–does this mean a new rear axle assembly, or just an axle shaft(s)? A new assembly is out of the question, since the truck is an '03, but dropping one out of a donor from the yard is a definite possibility. Let me know your thoughts.
Can’t speak to newer Ford trucks, but I believe the rear axle shaft on my older Ford truck can quite easily be replaced independent of the solid axle/differential ass’y. Finding a straight replacement axle that fits would be the challenge, not the replacement job.
You can find new replacement axle shafts for less than $100 if you choose to perform the repair yourself.
That’s what I’ve found as well…I’ve seen a lot of Youtube videos replacing axle assemblies, but haven’t found a quality video of replacing just the shaft on a ranger–I’m guessing the axle assembly still needs to be removed?
Well, the axle shaft has to be removed of course … lol … on mine to remove the rear axle shaft, all you have to do IIRC is to remove the brake drum, unbolt something involving the brake backing plate I think, 4 bolts, Ford provides a hole in the hub to do that. Then just pull the axle shaft out. It comes right out slick as a whistle, no involvement with the tube part of the solid rear axle. Maybe I had to use my home made slide hammer to get it to budge, don’t recall that detail. When I did it I didn’t have to completely remove the axle shaft, just get it free on the differential side bearing end, so there may be some extra wheel bearing/seal issues when for complete removal.
You must remove the differential cover, the differential pin and axle C-clip to release the axle shaft. No need to remove the complete rear axle assembly from the truck.
Merry Christmas everyone! Got the Ranger back on Friday, and while the shop did say they saw the rear wheels hopping while on the rack, their diagnosis was the front control arm, saying there was play in it. I thanked them, and paid for the diagnostic, but since the vibration is not in the wheel whatsoever, but in the seat, I wasn’t confident in the diagnosis–They said they believed the control arm issue was transmitting to the rear end. I definitely believe what they found, but I don’t think it’s the main culprit–this is a tricky issue, so I don’t blame the shop at all (and who knows, they could be right!)
I’ll try to get a video of the rear end moving up on jack stands, but I’m back to thinking about replacing the axle shafts.
If there’s play in the front control arm it must be replaced in any event. Safety issue. It makes sense to do that first, maybe it will solve the vibration problem too.
Did they put the rear wheels on a dynamic balancer?
I suspect that one of the rear tires may have liquid in it.
I’ve had all tires replaced (and rotated before and after).
So take it to a shop you have confidence in and see if they can verify Firestone’s diagnosis… or find the real root cause of the problem.