2016 F350 Constant Speed Vibration 42-45 mph
Symptoms: Vibration between 42-45 mph. The vibration comes and goes at that speed, starting off slightly then progressively increasing in amplitude, then fading back down and going away for a period of 3 sec- 20 sec. Customer also states that the vibration occurs at 85 mph but we don’t have any roads close by that we can safely drive that speed to test. Road surface doesn’t seem to be a factor. Cracks or uneven pavement don’t seem to cause the issue or change the amplitude. Vibration is felt in the seat bottom and seat back, is felt worse from the passenger seat than the drivers seat, and is worse in the back seat than the front seats. No vibration is felt in the steering wheel. Ford VCMM & accelerometers record amplitudes for the hop at .03-.11 and point to the rear of the truck. Ford says .05 and under is within spec. They have a TSB out for these symptoms that involves putting a caged damper on the drivers side of the trailer hitch. That TSB has been performed. If we remove the trailer hitch the hop increase in frequency up to .14 at times, and the speeds at which the hop occurs also increase to 42-48 mph, as well as the duration of time for which the hop is felt.
Conditions under which the vibration occurs:
- Speeds between 42-45 MPH;
- In 6th gear
- In 5th gear
- In 4th gear
- In 3rd gear
- In 4x4 with rear drive line removed
- In 4x2 with front drive line removed
- While the truck is towed down the road at 42-45 MPH with the engine running at idle with the transmission in neutral
- On a 4 post rack in 4x2 with the front drive line removed with the vehicle lifted from the axles and the tires not contacting any surface
- With a load of approximately 700 lbs in the back of the truck
- Rotated and balanced tires, no change in hop
- Changed wheels and tires from a 2020 F350. The tires were road forced prior to putting them on this truck. No change in hop
- Changed the driveline from a different 2016 F350, no change in hop
- Changed rear axle housing and ALL internal components, no change in hop
- Changed rear rotors, no change in hop
- Changed transfer case from another truck, no change in hop
- Changed transmission including torque converter, no change in hop
- Changed rear shocks, no change in hop
- Changed pinion flange, no change in hop
- Changed drive line u-joint operating angles to 6 different setups, no change in hop with any change
- Ride Heights have been verified within spec
- Alignment has been checked and verified good
- Parking brake pads backed all the way off to ensure they weren’t touching a surface causing a harmonic, no change in hop
- Performed a powertrain mount reset procedure, no change in hop
- Visually checked all cab mounts, exhaust hangers, cross members and spring shackle bushings
The above does not reflect the order in which procedures have been done but is representative of everything we have tried. At this point the truck has a new transmission, including torque converter, a drive line from a different truck, a completely new rear axle case and all internals, new pinion flange, and new shocks on it. It is back to the customers wheels and tires and we put his old rotors back on.
I’m pretty sure based on the way the hop comes and goes that we have a harmonic issue being created somewhere that isn’t getting absorbed. The setup on the rear axle has been rechecked 4 times now by 3 different people and we are confident everything is per workshop manual, and the contact pattern appears good. I have a hard time believing it could be rear axle at this point because we haven’t affected the hop at all. The probability that we got a bad part or incorrectly set up the rear diff the exact same way the factory incorrectly set it up to get the exact same symptoms is remote to say the least. Based on the fact that we get the hop while towing the vehicle in neutral and that it doesn’t change with RPM I have hard time believing it could be something in the engine causing it, not to mention I get virtually no vibration in the engine cradle when measured with the VCMM. I am confident it isn’t an aerodynamics issue due to the fact that we can duplicate it on a 4 post rack in the shop.
I got it to go away once with approximately a 700 lb load in the back of the truck. We started chasing drive line angles and shimming but couldn’t get any change. I put the load back in the truck to measure u-joint operating angles when the vibration wasn’t present and I could never get the truck not to vibrate again. It was the exact same load I had in the truck previously. I’m not sure if it was an aberration or not. Those tests were done on back to back days and the environmental conditions were very similar (dry roads and cool temperatures, less than 40).
Does anyone have any ideas on what could possibly be the root cause of this? At this point the only thing in the rear of the truck that hasn't been changed is the rear springs and the pickup box.
Look at the up and down play of the front axle it self at the inboard side of the u joint. especially on the passenger side. Some have a fair amount of play, I am dealing with similar issues in a 2017 F350 4x4 single rear wheel. It has manual hubs so next I am going to try manually locking the hubs to see if it goes away.
We get the vibration to occur on a 4 post rack with the vehicle lifted from the axles and no front drive line in it. Literally nothing on the front axle is turning and the vibration is present.
Hi Eric, just a thought seeing as you seem to have covered just about every thing else, could you have the wheels balanced on the vehicle. Not many on vehicle balancers about I know, on the vehicle balancing balances the wheel and drive shafts as well as I am sure you know. As I say just a thought regards Dave T...
Hi Dave. I haven't seen a on vehicle wheel balancer before and I'm positive I don't know anyone that has one. We have tried 3 different sets of wheels and tires, 2 brand new sets that we road forced prior to installing on the truck and we haven't changed the vibration/hop characteristics at all. I'm pretty positive we have a harmonic vibration that is being created in the ring and pinion that…
It's a long shot and somewhat of a band aid, but I would get a dampener and bolt it to rear diff housing and see if it made a change. The dampener on the transfer case of an 2016 f150 comes to mind as to something similar to what I would try. If it makes a difference it would confirm that it is truly a harmonics issue with rear diff. I feel sorry for u on this one buddy, I've been there.:(
Mike, That's pretty much what we're down to, a band aid. I had considered getting another damper from Ford and mounting it to the right side of the hitch opposite the one that is already on it. I have to modify the hitch to do so but I think that's where we are at. I hadn't considered trying to attach it to the axle housing. Probably can't do that long term but would be interesting to see the…
Eric , google Pico Diagnostics NVH kit . Stands for noise vibration and harshness ,also google on the vehicle wheel balancing. Just brain storming ! The pico scope kit looks interesting. Hope you get it sorted. Dave T...
David, I have the latest NVH tools and software from Ford. We are using the newest VCMM and accelerometers available.
With all that has been done or inspected, what’s left? I would give a thorough inspection of frame, cross members, springs, shackles, perches, fuel tank mounts, spare tire carrier, etc for cracks or broken bolts/rivets. Good luck and keep us posted. HTH
Tim, we haven't gone after fuel tank mounts, but we have loosened and inspected every cross member, all powertrain component mounts have been loosened, inspected, and reset, spare tire and rear frame mounted hitch have been removed. We've inspected all cab mounts. Now that I write this, this truck does have the 5th wheel prep package, I'm going to remove the hitch plate and retest. I doubt it…
I think that truck is flexing and may need another damper on it, very unfortunate to go through what you have already.
I think you're correct with the additional damper
I worked on a similar F250 4X4 truck several days ago. The vehicle exhibits a light hop at 45 to 50 MPH at light load. I tested the system with the ATS Intelligent Vibration Analyzer (IVA). This uses quad sensing technology, one sensor at each corner of the suspension. The data during the hop is shown in Figure 1 and Figure 2. There is no rotational vibration produced from any component. If any…
Bernie, Great info thank you. Based on our testing I think the resonant frequency begins in the rear diff. This is based on the fact that we can get the vehicle to exhibit the hop on a four post rack vehicle suspended from the axles via air jacks. It will hop at 44 mph in 4x2, but will NOT hop if we remove the rear drive line, engage 4x4, and drive the truck at 44 mph. It will also hop driving…
What is the engine rpm at the time the vibration happens? What is the hertz of the vibration? Are the any noises that occur at the time?
Engine RPM has no impact, it is only speed related. So output shaft in the trans to the rear diff. You can shift gears in the truck while the vibration is happening and have absolutely zero impact on the vibration. I will go back and look at the recordings for the hertz. No noises at all
Questions have you checked motor mounts , rear spring bushing. Have you tryed on the 4 post lift with drive lines out ? When u changed out transmission did flush the lines , was the fluid burned ? Cab and bed mount are they good ? Then what is road forced on the tire part you did ?
Motor mounts have been check and reset. Almost zero vibration in the engine cradle measured directly underneath the mounts. Rear spring bushings have been visually inspected but not removed. No vibration on the 4 post with the rear drive line out, but does vibrate on the 4 post with the front drive line out and the rear drive line in. Does vibrate on the road with the rear drive line removed. We…
On road force balance never heard of that , I am use to put on a balancer tire goes around then it tells u how much weight and were to place at Just thinking is frame stright . Are you able to check a 4 wheel alignment on it
4 Wheel Alignment is within spec, truck doesn't dog track. We can't measure the frame here but I have no reason to believe there is an issue there. Road Force balancing a tire spins the tire like a normal balancer, but then it applies pressure from a drum to the face of the tire and measures hard spots in the tire. You do a rim runout check and the machine tells you the optimal indexing of the…
And when the high spot is marked you can place it at the top of the tire when installing to maximize fitment on the hub. With the weight of the tire pressing the high spot of the Rim/Tire assembly to the hub, there is a tendency to have the wheel the slightest bit closer to the hub helping counter the high spot as well.
Just a thought. what about the leaf springs? Is it a dually? does it have the overload leafs? If so try ratchet straps around them inorder to cancel them out from vibrations. Also try taking the box off, sometimes the sides can do it too. We have before tried to hang weights and dampers on with straps before modifying them on.
Harm, I have been wondering about the leaf springs as well. I guess at this point it doesn't hurt to try. It is a single rear wheel truck that does have overloads. We aren't close to the overload touching when the truck is empty.
Yes we do. Using Ford's latest VCMM with vibration analysis software & accelerometers
This reminds me of the vibrations when the 2004 F150 body update launched. Indexing rims to hubs, road forcing tires, and hanging weights, It would always change but never fully go away. With this phasing in and out harmonics are likely the issue. Weight in the bed may not take the vibration away as it is isolated by mounts. Weight could be added to the exhaust and/or frame to see if you can…
What we have done in the past is drive it on the hoist in that vibration sweet spot and start hanging onto things in order to see if it changes. also using prybars to shift mounts. etc.
Chris, I'm 99% positive it is a harmonic frequency that is causing the wheel hop, and I'm 90% positive that harmonic frequency is being created in the ring & pinion. My problem is I replaced every single component in the rear axle. Housing, Carrier, Ring & Pinion, Axle Shafts, all bearings & cups, hubs, rotors, etc. Literally everything is new & I didn't change the wheel hop at…
If you think its in the rear axle would driving it through s bends on a road at that speed effect it? that should put a different load on the rear axle
Harm, I'll have to check. All our testing has been done on straight or gentle curves. I'll try to go drive it later to see if sharper corners make any difference in the vibration
Could you post any of your files showing frequency and amplitude?
I'll have to get screen shots of the recordings. All I have right now are raw data files and without the Ford software you wouldn't be able to view them. I will try to post later this afternoon.
I do have Ford software. Prefer the Pico software if you have it.
It won't let me attach the .vmm files, says it is unsupported. will have to do screen captures later on and drop them. I don't have Pico.
Fair enough. Look forward to seeing them.
Sorry it took me so long to post these, I had to get back out and do new recordings as another tech overwrote the previous file. You can see the frequency spectrum the vibration occurs at is pretty low. The software almost always picks on tires (sometimes drive line). Smooth newer road is where the issue is, cracks or bumps actually make the truck drive better.
I am guessing if there was any AM suspension it would have been mentioned but I still have to ask?
Good question, I didn't speak to that. The truck is completely stock with the exception of an aftermarket aluminum front bumper. We initially thought that might be changing some aerodynamic properties and contributing to the issue, so we put a stock front bumper on and had no change. We also yesterday added a second harmonic damper to the right side of the trailer hitch per Ford engineerings…
i think the truck is trying to tell you something? built on a friday or monday. Basket case? How is the customer?
Hi Eric. Hopefully this one has been sorted out by now, but in case it hasn't. Have you tried another new damper from Ford yet? I was just watching Bernie's video he posted using his tool to identify the vibration. I haven't seen one of these dampers yet and it is a pretty beefy complex unit. I was impressed at how flexible it seemed to be and easy to flex and rotate. I'm wondering if you…
We did try a new damper, even modified the trailer hitch and added a second damper to it trying to knock the hop down to an acceptable level. Even with the second damper on the amplitude of the vibration is almost double what deems normal.