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My Theory on the "Superduty Hop" and Possible fix.

538K views 1K replies 178 participants last post by  Jdaniel 
#1 · (Edited)
Hey everybody, I'm starting this thread to show my theory of the SuperDuty Hop that's common on our trucks. This problem has spanned many years from what I've read and people I've talked to, but this has been most prevalent in the CCLB Super Duty platform. From 2000's with 7.3s to 2014s with 6.7s and all years in between there's a bunch of folks who seem to have this problem.

This isn't death wobble. That's the intense shaking of the front axle back and forth, due to front end parts being loose like ball joints, track bars, etc.

This is the weird vibration that feels like the rear end is hopping. It happens when driving down a straight road at a speed of usually 40-45mph, and when it's bad enough, you can see it. People with it can drive under that and its ok, then it comes on around that speed, then goes away once you get above it. That's ok for most folks, but for some of us with 45mph speed limits in areas, it really sucks. Check out these threads for more info.

http://www.powerstroke.org/forum/6-0-drivetrain-problems/508202-rear-end-hop.html

Rear end bounces @ 40-45 MPH - Ford Truck Enthusiasts Forums

Wheel hop/ back seat shake - Ford Truck Enthusiasts Forums

There's a bunch more, just check out google.

Most of the time, this gets (IMO) misdiagnosed as an unbalanced driveshaft, bad shocks, warped rotors, bad springs, etc. People spend a lot of time and money replacing these things and yet still have the same problem. Ford even came out with a TSB for us 05-07 guys that involves a $450 damper kit that attaches to the rear driveshaft and is supposed to fix it. Well guess what, it doesn't. Mine has this damper and it still has the hop.

My primary mechanics specialty is suspension/brakes/steering, with engines as a secondary. I've done a lot of work on a lot of different vehicles and have come up with a running theory that until now, I wasn't so sure was even in the ball park, until I talked with a member on here, Mhatlen. He thought along the same lines as me and had done some work on his truck and it got rid of the hop.

My theory is that it's not the drivetrain or axles that are vibrating/hopping, but the frame itself flexing........think like a large I-beam only supported by the ends and you jump up and down in the middle. Especially under a CCLB, there's a ton of open frame area that has no crossmembers, and I don't think the stamped crossmembers running across the top of the frame in front of the fuel tank/front axle are working well enough. They're holding the frame well side to side and back and forth to a degree, but they don't hold it that well from flexing up and down.

I started thinking this because I can't believe there are that many faulty springs/driveshafts/axles causing this issue and it seemed to be the only thing that would explain the wide range in years that this happens to.
 
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#2 · (Edited)
So, after talking with Mhatlen and seeing that he too thought this and had actually made a fix on his truck, I got motivated and started outside. I wanted a few things out of my fix.

1) A bolt-in application with minimal modification to the frame

2) Semi-easy to duplicate/modify to work for many years

3) Of course, I want it to get rid of the problem

So first off, here's a pic of underneath my truck. 2005 F350 4x4 6.0L Auto CCLB





Don't mind the oil spots....at this time I had already been spraying some penetrating oil. As you can see, it's a big blank space without any support. I was first going to build a support right in the middle here, but there are a lot of products that people use that fit in this big blank spot so nicely. Air compressors, aftermarket fuel/water separators, extra battery trays for trailer haulers.....some people actually already have this space full so that was out. So I decided that I'd try to just reinforce the crossmember that's in front of the fuel tank. This probably won't work for anybody that has a bigger aftermarket fuel tank, but I figure there's less people that do a bigger underbody and they just do a transfer tank in the bed.

I'm making this out of 2" OD 0.25 wall DOM tubing and some 1/4" steel plate. Not the best saw to cut DOM with, but it works



Two 6" long pieces with a 45 degree cut on each end.



After cutting, they get beveled with a grinder for better penetration and more strength when they're welded together.



The steel plate, drilled to the pattern on the frame....ish (found that out later :doh).



Ok, here's where I got really into doing this and forgot to take some pictures. I'll go out and take some more when my camera charges up, but for now here's some with some steps skipped. There's a bunch of small holes in the framerails right in front of the fuel tank. I took 4 of those holes and drilled them out to 1/2". On the drivers side, there's some fuel/electrical lines so you gotta be careful, on the passenger side, just the exhaust hanger. I unbolted the exhaust hanger and trimmed the steel plate to fit the bend in the frame, then transferred the pattern to the other plate. The nice thing is you only have to do one side, then just make a mirrored version for the other side of the frame.

Here's a pic of the holes in the framerail. These holes are already there, I used a reamer bit to open them up to 1/2" and used grade 8 hardware to hold it together

Drivers side:


Passenger side:


With the plate in, I want the tube to be angled up and towards the rear. This should let the crossmember work on both the horizontal axis and the vertical axis. Towards the front would work just fine too, but going towards the rear was easier because the carrier bearing was in the way.

Tacked up





I did the other side too, but that's one of the things I forgot to take a pic of.

This is where I ended up today.....



I'm waiting on some more DOM tubing and some gas for my MIG welder....in case you were wondering why the tack welds looked like crap :doh: Also, you can see where my holes "missed" and I had to drill new ones. This will be fixed as well.
 
#5 ·
My truck does the same thing but is intermittent. Tires were just road force balanced and they are perfect.
^^Same here. Tires are balanced, driveshaft is balanced, no u-joint problems. Obviously yours doesn't do it Rob or you wouldn't be so quick to say it's a waste. I'd bet that's because of your suspension work. From what I've found out, folks that have an upgraded suspension package seem to have this problem less, but I think there's more to it than that. Either way, its my effort to waste and if it works great, if not, too bad I'll post results either way.
 
#6 ·
Not trying to be abrasive guys, just saying Donahoe racing and many others have run the Baja 1000 on Superduty frames both modified and stock. Amy good shop could find your problem in under 2 hours. Your local ford dealer is not the shop I'm reffering to. I'm in DC till July then Vegas after that, also in NM for aug and sept. if you anywhere close we can hook up and I can help you.
 
#9 ·
No problem Rob, I see where you're going with that, and I've tried a few shops, but they've all told me the same thing. Tires/driveline out of balance, bad shocks, even done some experimenting with changing pinion angles and nothing's seemed to make it 100% better or go away. I'm not saying that the frame is weak, I just think that it starts to bounce as the suspension stresses on it, causing the "rear end hop" that a lot of people see/feel.


Your definitely not doing any harm by reinforcing the frame. I have my front end reinforced pretty good tying bumper mounts to shock mounts. The Rize link cage I have also connects the frame crosswise in two locations under transfer case. I actually have rear bracing too, I have the fifth wheel attachment that uses 1/4 steel plate for 20 inches along frame rail in rear and is connected by the two rails horizontally. Worth the effort if you've already tried the other stuff and done the research
Again another reason why I figured that your truck wouldn't have this problem :lol: I knew it was already beefed up pretty well.

No wasted effort in beefing up the chassis. These frames do move all over the place depending what your doing with the truck. Surely everybody feels the frame bounce in these Superduty's when hitting a dip in the road etc. I myself call it frame bobble because it doesn't want to do it only once. Like a bobble head lol.
I am very interested in how you go about it with your truck. I have installed 3 additional crossmembers in my truck and reinforced my transmission crossmember. I tied it in with diagonal bracing to each frame rail. Also installed one of the crossmembers if you want to call it that between the radius arm hangers. From there back to the transmission crossmember.
The truck handles completely different now and without the bobble. It really tightened up the steering. These trucks flex around more than you know and it plays a part in how they handle. You tighten up the chassis and it will tighten up the handling.

I think the crossmember that you are doing your work near is a good one to experiment with a stiffener. Making the driveline carrier mount much more solid may have a positive difference.
Keep the pics coming your not wasting a minute of your time.
I know this is an apples to oranges kind of thing, but in my experience Fords have always had a twisty shifty frame when stock. I have an '87 bricknose that when articulated, the frame twists enough for the bed to touch the cab, and that's on Deavers front and rear. The OBS platform got a little better, and the Super Duty's are even better. I've had this one articulated pretty well and the bed only gets about 1/2" out of line with the cab. It's not much, but that 1/2" is proof to me that that loooong frame is still twisting when the suspension is putting some stress on it.

So, my thinkings that if it can twist, it can bounce (if you can dodge a wrench you can dodge a ball). I'd absolutely love to have a GoPro or something like that to mount underneath a couple of trucks with this problem and actually get a good look at what's happening in real time, but that'll have to be for the more privileged lol. Even if it is a waste, like I said its my time to waste.....gives me something to do in the afternoons lol.
 
#7 ·
Your definitely not doing any harm by reinforcing the frame. I have my front end reinforced pretty good tying bumper mounts to shock mounts. The Rize link cage I have also connects the frame crosswise in two locations under transfer case. I actually have rear bracing too, I have the fifth wheel attachment that uses 1/4 steel plate for 20 inches along frame rail in rear and is connected by the two rails horizontally. Worth the effort if you've already tried the other stuff and done the research
 
#8 ·
No wasted effort in beefing up the chassis. These frames do move all over the place depending what your doing with the truck. Surely everybody feels the frame bounce in these Superduty's when hitting a dip in the road etc. I myself call it frame bobble because it doesn't want to do it only once. Like a bobble head lol.
I am very interested in how you go about it with your truck. I have installed 3 additional crossmembers in my truck and reinforced my transmission crossmember. I tied it in with diagonal bracing to each frame rail. Also installed one of the crossmembers if you want to call it that between the radius arm hangers. From there back to the transmission crossmember.
The truck handles completely different now and without the bobble. It really tightened up the steering. These trucks flex around more than you know and it plays a part in how they handle. You tighten up the chassis and it will tighten up the handling.

I think the crossmember that you are doing your work near is a good one to experiment with a stiffener. Making the driveline carrier mount much more solid may have a positive difference.
Keep the pics coming your not wasting a minute of your time.
 
#10 ·
I'm interested in this myself and I only have a Single cab. I've loosely chased this problem for the last 2 years but haven't come up with a solution.

Right at 60km/h the truck bobs. I've had a new driveshaft made ( for the lift), 31's, 35's, and now 37's all dynamic balanced so dead perfect. Rear suspension completely rebuilt (lift blocks to spring and shackle lift)

Nothing ever seems to touch it, rotating the tires, paying to have them balanced the normal way ( which sucked on the 37's). I borrowed some stock tires to drive on for a day and it made no change.

Only thing that seems to make a difference is it got WAY worse when I had the gas tank skidplate out, which makes me think you ARE on the right track.

I would also really like some of the 08+ guys to chime in, I wonder if the goofy un centered leaf springs that our older trucks have make a difference. 08+ the front hangar is 8" IIRC farther forward because they lengthened the spring to where, I think, it should have always been
 
#11 ·
I haven't talked to or heard of many '08-'10 SDs that do this (and that doesn't mean they're not there), but the 6.7 guys seem to have this problem too.

If you read through the "Rear end bounces" thread that I posted up above, those guys actually got the opportunity to have field engineers from Ford come out and look at their rigs with vibration/harmonics equipment. After trying different driveshafts/axles/tires/wheels they came up with that it's the "nature of the beast in a heavy duty truck" which I can't believe.

Some have said with weight in the bed it goes away, and some have had it happen even with weight in the bed. There doesn't seem to be any rhyme or reason as to why some trucks do it and some don't. Maybe they've been put through something in their lives....IDK.

Going to the steel yard today to check on my order.
 
#228 ·
I have a '05 F250 CCSB 4wd that does this. My body mounts are completely shot though.

I haven't talked to or heard of many '08-'10 SDs that do this (and that doesn't mean they're not there), but the 6.7 guys seem to have this problem too.

If you read through the "Rear end bounces" thread that I posted up above, those guys actually got the opportunity to have field engineers from Ford come out and look at their rigs with vibration/harmonics equipment. After trying different driveshafts/axles/tires/wheels they came up with that it's the "nature of the beast in a heavy duty truck" which I can't believe.

Some have said with weight in the bed it goes away, and some have had it happen even with weight in the bed. There doesn't seem to be any rhyme or reason as to why some trucks do it and some don't. Maybe they've been put through something in their lives....IDK.

I had a '99 Dodge Cummins ECLB 4wd several years ago that had a 40-45mph severe hop. With less than a 1/4 tank it and your arm on the middle console it you couldn't read your phone going down the road, water in bottles would be shaking all over.

Full tank it wasn't as bad, it had a gooseneck in the bed and with a trailer on it would hardly do it. Tires didn't matter, new Bilstein shocks, new u-joints, carrier bearing, etc etc.

It did it less when I had a passenger in the front seat.

Seemed to be more with the 5speed trucks than it did with the Autos... there are several threads on the dodge forums about it also, I started one a while ago that I still get email replys on... I am wondering if the tranny crossmemeber was different between the two, or maybe the auto weighs more, pulling down on the frame.

Either way, I am going to guess the long beds have this issue more due to the longer frames and the beds don't really provide much rigidity.
 
#13 ·
In it to win it! :thumb: :D
 
#18 ·
How are you going to tie the two frame rails together ?

90 degrees straight across or at a angle? Have you pondered doing a X type of cross connection? I know it would be much easier if you could get rid of that driveshaft and exhaust pipe. :)

I'm watching with mucho enthusiasm. I'm still interested in strengthening of the crossmember that has the carrier bearing tied to.

Keep the pics coming
 
#23 ·
What I will say about jetjock is he has been all over the map with opinions back and forth.

I know for fact it's not a rotating issue. As far as some trucks do it when others don't I think it comes down to variations in the steel being used for the frames. It's a lineir issue with the frame rails for sure.
I have done some frame bracing and I went after it starting at the radius arm hangers. That is where the full box ends and where the flexing starts. I feel like it is really starting at the point where the radius arms connect to the frame. There is a lot of pressure at that point of the frame, it's a lever point! My theory is the problem starts there and ends around the rear leaf hanger. Tighten up that area and you will stop the flexing/oscillation.

I will look into loading pictures instead of thumbnail and post up my chassis solution. There may be a easier way to accomplish it but it worked for me.
 
#25 ·
Your right I have not experianced even though I've done suspension work on countless SDs. It's not a difficult concept to isolate, your on the right path of locating the issue by runnin without the rear driveline. I've built off road vehicles from the ground up where we set castor, camber, toe, width, suspension travel and scrub. A leaf sprung solid axle rear end is as easy as it gets boys. If I had the problem or a friend in need, i'd solve it in a day - it's not rocket science and you seem to be making progress towards isolating the issue. Im not able to offer much advice from afar, and that's been noted, so ill stay clear of this one.
 
#26 ·
Didn't mean for anything to come across as an attack Rob so I'm sorry if it did. I'm just trying to tell you that "all the usual suspects" have been crossed off the list. You're right it's not rocket science but its an anomaly that's for sure, and the reason I said I just have a theory. I've got no way to prove it, but with everything else crossed off the list what else could it be?
 
#31 ·
Or frame flex. Removing the skid plate on my truck (too excited to drive the truck after hutch mod and secondary fuel pump install) made my trucks hop worse. But nothing has made it better, or for that matter, nothing else has affected it in any way.

I have:
3 completely different rear suspension configurations in the last 3 years. Currently 5" superlift soft ride leafs with PMF's 4.5" shackle flip and the factory lift block removed.
4 different sets of tires. Stock, 31's, 35's, and 37's.
Stock driveshaft-> custom driveshaft -> recently re shortened and balanced custom driveshaft.
Poly bushings in most of the suspension, more as my ambition allows.
4 wheel alignment done, they said it was just fine

Like the OP, I have done all your basics, and nothing makes any change

I'll give the binding stuff down a shot tomorrow
 
#32 · (Edited)
You never know this may be the start of: NightHawk F-Series Frame Solution Bracket Assy

I'm starting to think this is much more common then I thought. With my truck I figured it was because of the larger tires. I drive F350 duallies at work and never felt it. But they are always loaded down with a service box so maybe that is the difference. ?

Another thought I tossed around was mating up some 1/4 or 3/8 plate down the outside frame rails. But there are so many rivets and stuff on it I myself gave up on it.
A suspect area to me was where frame moves up for the rear end. But I have no real idea if it is a possible problem ares or not. ??
Working on your back under the frame is not fun or easy.
Good luck on finding the "B" Spot. Bobble :)
 
#33 ·
#35 ·
It's in the wrong place for one, between the rear leafs is not the spot. IMO

It's the long distance between the suspension connections. My truck I felt the frame flexing like a leaf spring in its own way. Surely if someone set up sensors and shot lasers down the length of frame you would see the frame bounce. It's moving and it's designed to the problem comes in when it becomes a cycle or oscillation. If you shorten the distance of the frame area that can flex it is much less likely to do it.
NightHawk is right IMO the problem is the span of frame hangin out there with little and no cross bracing to control it.
I tied frame together from radius arm hangers back 18" behind transmission crossmember. Problem solved. Was a fair amount of work, also installed two more top and bottom at output shaft for good measure.

He's going to get it, hopefully doing it in one connection unlike me with four.
I'm patiently watching.
 
#34 ·
Use a gopro or contour hd with a suction cup or zip ties and take multiple videos from different angles. That should be sufficient evidence to what is going on.


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#37 ·
The guys with 6.4s (myself included) experience a similar issue.

I have, I think, narrowed it down to the natural (resonant) frequency of the drivetrain/frame. Never underestimate the subtlety and violence of natural frequency events (Tacoma Narrows bridge anyone? )


The problem seems to arise for most guys with stock set ups (tires suspension) around 1700-1750 RPMs (40-45 MPH 4th gear). I notice I can also induce it around 1700-1750 in 5th gear (65-70 MPH) (though nowhere near as pronounced).

Check your RPMs when it begins to do this and try to induce it on a smooth road with smooth, progressive inputs. I've seen as low as 1600 RPMs.

Those of you with non-stock set ups have possibly moved the conditions that cause that NF to resonate to its peak or have dampened it some with your changes. It becomes really hard to narrow down at that point.

If you were to tie the frame together with a crossmember, it would change this frequency as well. It could eliminate it or just move it into another range that you may or may not ever notice.

So, the best way to diagnose this as a group is sampling the largest group possible with identical [or nearly identical] set ups. That's usually the stock truck group. Though, keep in mind, even in this group there are significant variations from tires to mileage on components like shocks and bushings [this can sometimes be a huge variance].

So, see if you can get the same results at about 1700 RPMs in 4th and 5th. Try to make sure your truck is unloaded also and keep note of your tire pressure. Mine was worse when the tire pressure was around 80 and calmed significantly around 60 psi.

I changed my shift points in the truck and the bounce/vibration is gone.
 
#38 ·
Doss has hit the nail on the head:nod:

It's tire harmonics that is causing this bouncing we get at 40-45mph and this was explained too me by the tire shop manager at work (costco) and there is basically nothing that can be done about it.
 
#41 ·
By reading everything in this thread I think everyone's input has solved the issue.

Tire harmonic I believe is the root cause. Does it seem to be more related to CCLB?

But the OP's ideas are on the right track to actually be able to cure it. I think if you can make a new trans crossmember and box in 4-6' section in the middle (say from the front end of the fuel tank to the center post of the cab would be sufficient) along with better progressive rear leafs and quality shocks would eliminate it.

Lol. I think I found a new product to add to my welding/fab shop. :D

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