Wheel hop, axle wrap...

[TwinStick]

https://www.youtube.com/watch?v=vS_5xwt1_io

https://www.youtube.com/watch?v=ZLdhpT2OM-w

https://www.youtube.com/watch?v=ZLdhpT2OM-w

https://www.youtube.com/watch?v=mHyEk4Av4-Q

For those that don't know what axle wrap is. ^^^^^^^^^^^^^^^^

[nts007]

I dunno about more power being a fix lol once te wheels are spinning fast enough your fine but you also have to remember your running a 37" tire with a much larger sidewall then most people on here that are having wrap issues. You probably don't run your pressures at 60psi all the time either


Sent from Canada

Now who would do that. Besides my max inflation is 50 lol. And I'm running 40r 45f unless I'm towing then the rear goes to 50. Then again I can't go out now and show u cause this fantastic wimpy 3 inches of snow would do it justice. Now don't get me wrong I'm loving this weather. It beats -40 any day of the week.

Lol back to topic

The torque fork idea has been in my mind since I've had my 06 PW. I do remember axle wrap but it wasn't terrible. But it existed. So some kind of ladder bar would be the direction I would go. If not a full real 4 link like what BAANG did. As far as the new trucks wouldn't a lower control arm mount mod work. Grabbing the axle lower instead of being nearly 90° from the upper mount be more 180°. And maybe increase the height of the upper. I know it will affect geometry but how bad could it be. It's almost the older trucks front end setup on the rear of the new one. Hell. Wouldn't a full on swing arm rear do even better like the trophy trucks.
Sure it would be rougher but hell its a TRUCK it should ride like one. It's not a Lexus

[JBM Power Wagon]

It's still the same issue as the 3rd and 4th gens and every truck with a lot of power a high gear ratio and leaf springs experienced before. Play with the tire pressures and if possible try locking up the rear also. If the truck is in full spool in the rear it won't want to hop as much either. JBMs wagon is a 5th gen radius arm truck and he airs his 35's down to 20psi and has no wrap whatsoever when he's with us either in the snow or the dunes

ImageUploadedByTapatalk1452261129.465772.jpg

Sent from Canada

Yup, air down to 15-20psi and it will just about eliminate any axle hop in snow. It worked in my 2011 PW and my 2014 PW. When aired up the type of snow makes a HUGE difference on how much axle hop you will get (none to shake your teeth out).

[adeluca73]

Wrap and hop are two different phenomenon. They are caused by two different mechanical processes. Wrap should be exclusively and inexorably the inviolable product of rear leaf suspensions with opposing shocks. The new PW 4 link, spring/shock, center shock set-ups shouldn't be victim of torque induced axle twist/untwist. Under local acceleration with varied traction L/R, the springs arc like a sideways "S" about the center of the stack, with random pinion angle changes, thereby taking the axel on its side of the diff w/ it, resulting in twist & storing of kinetic energy. In vibrations, masses store & release kinetic NRG, springs store & release potential NRG, & dampers dissipate NRG by attenuation of velocity & converts it to heat within the viscous fluid of the shock. Once traction or linear acceleration change, the mass of the axel twist unloads, creating an angular acceleration & you feel the violent wrap. Taller tires, bigger rear gear ratio, high engine torque (eng Tq X 1st gear X xfer ratio X rear ratio X wheel size X the offset angle of any additional lift blocks) and heavy tires will rapidly deform your leafs & result in wrap.

Hop is different, harder to ID the culprit, and as a consequence, harder to control. The problem is contact patch duration, under rapid acceleration from rest or a slow roll, the instant center shifts away from the vehicle CG, track bars or control arms resist this change, and it works in RWD muscle cars, 8K# trucks w/ 410HP...not so much. Shock wear & tire pressure can really help/hurt hop. Under rapid acceleration from rest, the tires have 100% effective contact patch, and the normal force is perpendicular to the contact patch, then the tires move slightly forward in the wheel well, the tires normal force isn't 100% perpendicular, tire toe angle dynamically changes, tires loose some traction, then the onset of slip, followed rapidly by spin, the resultant angular acceleration decreases, especially if there's a limited slip type diff, which corresponds to a decrease in linear car acceleration, which restores the static toe angle, the wheel moves back to its static center, & you feel hop, wash/rinse/repeat several dozen times a minute.
Tire pressure & stiffer suspension bushings (very hard, stiff polyurethane) can help reduce this, the key is to reduce wheel movement w/ respect to the frame.

But I'm not a mechanic either

[2wagons1driveway]

Patton fabrication makes some LT traction bars for those in the market. He does killer welding and is an awsome fabricator. His traction bars are used on dodges with 18+ inches of travel so they will allow flex to the max still and are high clearance to avoid getting hung up on rocks. I've only ever seen them on the leaf spring trucks but they would probably work fine on the coil spring rears also


Sent from Canada

[Will]

I've had my front axle hop in sand, the new rear is more than likely hopping, not wrapping.

[GunniPWguy]

Wrap and hop are two different phenomenon. They are caused by two different mechanical processes. Wrap should be exclusively and inexorably the inviolable product of rear leaf suspensions with opposing shocks. The new PW 4 link, spring/shock, center shock set-ups shouldn't be victim of torque induced axle twist/untwist. Under local acceleration with varied traction L/R, the springs arc like a sideways "S" about the center of the stack, with random pinion angle changes, thereby taking the axel on its side of the diff w/ it, resulting in twist & storing of kinetic energy. In vibrations, masses store & release kinetic NRG, springs store & release potential NRG, & dampers dissipate NRG by attenuation of velocity & converts it to heat within the viscous fluid of the shock. Once traction or linear acceleration change, the mass of the axel twist unloads, creating an angular acceleration & you feel the violent wrap. Taller tires, bigger rear gear ratio, high engine torque (eng Tq X 1st gear X xfer ratio X rear ratio X wheel size X the offset angle of any additional lift blocks) and heavy tires will rapidly deform your leafs & result in wrap.

Hop is different, harder to ID the culprit, and as a consequence, harder to control. The problem is contact patch duration, under rapid acceleration from rest or a slow roll, the instant center shifts away from the vehicle CG, track bars or control arms resist this change, and it works in RWD muscle cars, 8K# trucks w/ 410HP...not so much. Shock wear & tire pressure can really help/hurt hop. Under rapid acceleration from rest, the tires have 100% effective contact patch, and the normal force is perpendicular to the contact patch, then the tires move slightly forward in the wheel well, the tires normal force isn't 100% perpendicular, tire toe angle dynamically changes, tires loose some traction, then the onset of slip, followed rapidly by spin, the resultant angular acceleration decreases, especially if there's a limited slip type diff, which corresponds to a decrease in linear car acceleration, which restores the static toe angle, the wheel moves back to its static center, & you feel hop, wash/rinse/repeat several dozen times a minute.
Tire pressure & stiffer suspension bushings (very hard, stiff polyurethane) can help reduce this, the key is to reduce wheel movement w/ respect to the frame.

But I'm not a mechanic either

You wouldn't get paid enough if you were.

[nts007]

This is a fun thread. Let's stir the pot.

Why do the gas jobs (less torque) and not the diesels (more torque) get the shock. Based on what you just said then big tires and more power make it worse. But in practice it seems opposite.

Go

[Will]

Gas is more responsive off idle? I agree bigger tires make it better due to more traction, more sidewall flex, cushion, etc...

[adeluca73]

This is a fun thread. Let's stir the pot.

Why do the gas jobs (less torque) and not the diesels (more torque) get the shock. Based on what you just said then big tires and more power make it worse. But in practice it seems opposite.

Go

Make which worse---hop or wrap ?

[adeluca73]

This is a fun thread. Let's stir the pot.

Why do the gas jobs (less torque) and not the diesels (more torque) get the shock. Based on what you just said then big tires and more power make it worse. But in practice it seems opposite.

Go

Effective torque to the rear end...most diesels have a 3.73 or 3.53 rear end from factory, right, not 4.56's, plus new trucks don't have leafs, & diesels have rear leveling air bags now, so who knows at this point.

[MoparToYou]

I've had my front axle hop in sand, the new rear is more than likely hopping, not wrapping.

If it is hop, then why does it feel just like wrap on any other vehicle? I suspect they may feel the same. And also, if it is hop, then why did the Ram engineers think it was wrap, and add the center shock to help decrease the effect of axle wrap? Possibly because they're the same engineers that weren't smart enough to design a system without the problem in the first place.

I'm the one that just went through a bad case of this yesterday, and to me it feels like axle wrap. I think the reason I had such a problem, was largely due to snow conditions. Snow that falls when it is exactly 32 degrees, as this did, tends to be very wet and heavy snow, which this was. The wet and heavy snow is hard to drive through because it is so dense, and when it packs it turns into a layer of ice. That is why I thought the Goodyear Duratrac's sucked so bad, because of the snow conditions. They're supposed to be a pretty decent snow tire, but they sure didn't work worth a crap yesterday. And the snow conditions are why the truck had so much axle wrap, the snow conditions turned a potentially bad problem into a really bad problem, that left me definitely underwhelmed with this trucks performance.

And speaking of axle wrap, I have an idea that might be a quick and easy fix. My truck is still all snow and ice underneath, but when it thaws out I need to look at the frame mount for the axle anti-wrap shock. If it is like the mount on the axle, It would be very easy to convert a single anti-wrap shock into a dual anti-wrap shock. Just install a sleeve in the bracket where the shock normally goes, and using a longer bolt, install a shock on each side of the bracket, instead of a shock in the middle of the bracket. Both shocks, the bracket, and the sleeve inside the bracket would all be held in place by the longer bolt. Running dual anti-wrap shocks might help somewhat. Add larger tires that are aired down, and with better snow conditions, this might not be as big of a problem.

[adeluca73]

I've had my front axle hop in sand, the new rear is more than likely hopping, not wrapping.

If it is hop, then why does it feel just like wrap on any other vehicle? I suspect they may feel the same. And also, if it is hop, then why did the Ram engineers think it was wrap, and add the center shock to help decrease the effect of axle wrap? Possibly because they're the same engineers that weren't smart enough to design a system without the problem in the first place.

I'm the one that just went through a bad case of this yesterday, and to me it feels like axle wrap. I think the reason I had such a problem, was largely due to snow conditions. Snow that falls when it is exactly 32 degrees, as this did, tends to be very wet and heavy snow, which this was. The wet and heavy snow is hard to drive through because it is so dense, and when it packs it turns into a layer of ice. That is why I thought the Goodyear Duratrac's sucked so bad, because of the snow conditions. They're supposed to be a pretty decent snow tire, but they sure didn't work worth a crap yesterday. And the snow conditions are why the truck had so much axle wrap, the snow conditions turned a potentially bad problem into a really bad problem, that left me definitely underwhelmed with this trucks performance.

And speaking of axle wrap, I have an idea that might be a quick and easy fix. My truck is still all snow and ice underneath, but when it thaws out I need to look at the frame mount for the axle anti-wrap shock. If it is like the mount on the axle, It would be very easy to convert a single anti-wrap shock into a dual anti-wrap shock. Just install a sleeve in the bracket where the shock normally goes, and using a longer bolt, install a shock on each side of the bracket, instead of a shock in the middle of the bracket. Both shocks, the bracket, and the sleeve inside the bracket would all be held in place by the longer bolt. Running dual anti-wrap shocks might help somewhat. Add larger tires that are aired down, and with better snow conditions, this might not be as big of a problem.

I can't comment on the ass-feel of one vs. another, I just know physically what's happening from an engineering perspective. The new suspensions should not see wrap, they just don't. Wrap is derived from angular torque of the axle from the diff out to the tire due to deformation of leaf springs under heavy acceleration. Can the axles twist some w/ the new rear, I guess, but I suspect it was more hop than wrap. Especially if you didn't air down, the snow was wet & heavy, & you were hitting the throttle hard, you were most likely slipping & spinning a bit, which was moving your wheel w/ respect to the frame. Be interesting to see a video of it in action

[loveracing1988]

This is a fun thread. Let's stir the pot.

Why do the gas jobs (less torque) and not the diesels (more torque) get the shock. Based on what you just said then big tires and more power make it worse. But in practice it seems opposite.

Go

Effective torque to the rear end...most diesels have a 3.73 or 3.53 rear end from factory, right, not 4.56's, plus new trucks don't have leafs, & diesels have rear leveling air bags now, so who knows at this point.

Ok, diesels get a 3.42 gear now in everything but drw applications where they get 3.73 to 4.10. Also the rear leveling bags are not standard with the diesel, they are still an option like with the other 2 engines.
The reason the diesels do not get the shock is pretty much what someone said above, the gas engines are more prone to wheel hop than the diesel trucks. The gas engines have less torque but the throttle response makes it hit more instantly, the diesel on the other hand has to spool the turbo and they are pretty heavily affected by torque management to protect the Drivetrain.

[nts007]

Alright so let's keep the fire burning. Effective gear ratio should be a non issue as other than the PW other hemi powered trucks have 3.73s ect.

So here is my response. Axle wrap is the primary cause of rear leaf sprung rear end wheel hop.

Under acceleration the rear axle twists toward the rear by which the top of the axle moves toward the rear.

The (dampener) in the new design is a bandaid fix that does a poor job at fixing it anyway.

Dodge could have easily done a super flexy 3 link setup or a 4 link that would have near zero axle wrap.

Dodge didn't do it cause improving leaf spring designs is always too much of a compromise.

Chrysler needed something that looks super modern and fancy to resell their brand as future minded

To match the feat that 6 bushings and 2 leaf springs does they had to design a system that has 14 big rubber bushings.

Dodge doesn't think about the 5% of us that truly use our truck off road more than 5% of the time that it mattered if the design didn't make things better for 'us'

Complexity brings more future money. Why not use poly bushings instead of rubber. Wells Chrysler has a whole chapter and course specifically dealing with NVH where they will pick apart every little vibration or noise or bump. Hell I'd bet they know at what frequency the bed bolts will vibrate and back out but more important at what level vibration in the chassis crossing over a moderate railroad crossing that you will spill your latte moca coffee thingy.

But back to the rear axle. Correct me as I'm invisioning the motions in my head. Axle twists top to the rear, the lower control arm axle bushing just pivots up cause it's only job is to stop forward back motions(even though if it was say under the axle it would also do this), the upper axle bushing is being 'pulled' rearward thus transferring the rotating force of the top of the axle into the chassis mounting bushing. Say 1/8" allowed flex per bushing per direction so 1/4" per bushing. 2 bushings...1/2+" of forward back rotating motion due just to bushing flex per link

So how the f does the "dampner" do anything in 1". Hell it has 2 bushings so figure almost the same amount of bushing flex.

A solid bar from the top of the axle "dampner" mount that shares the same length and same parallel position of the upper control arms would cut a shit ton of that movement.

Now I know I'm shooting this all over the place but we have a very knowledgeable team here and I would bet good money that we could have done a ton better job then they did designing the rear axle setup.

-Based on our needs-

Kelderman makes a 5 link system to work with their air ride rear end and it works like a damn removing the rear leafs.

So why. Why does Chrysler make this shit. Balljoints that fail in 15-30k miles. Tie rods that take 2-3 recalls and still not fixed.

Well it keeps the aftermarket in business eh.

Alright let's go. Keep this goin

[olyelr]

Yeah, it is hop more-so than wrap. They both feel very much alike.

My jeep will do it in certain scenarios (typically in certain sand or deep snow conditions), and it has 4-link front and rear (5 link with the track bar) with rod end type connections, not rubber bushing's that allow any flex or movement. The axle simply cant wrap at all. But it will still hop.

Someone needs to get their go pro mounted under there so we can see it first hand.

[olyelr]

So how the f does the "dampner" do anything in 1". Hell it has 2 bushings so figure almost the same amount of bushing flex.

Good question. One I have pondered since I saw that stupid thing.

The only way that thing moves at all is if the axle rotates. But with a 4 link, the axle DOESN'T rotate. Depending on the link placements, there may be some very minor movement to that shock during its full suspension cycle, but I bet it is very minute.

I would like to see a go pro pointed at that darn shock under heavy use, too.

[adeluca73]

I have to edit my Students Masters Thesis right now, too much time pontificating the theory of how my off-road hobby can improve...my research projects are far more cool: flapping engineered Manduca Sexta hawk moth wings, X-56 aileron eliminating wing camber morphing, new Air Force tactical tanker effectiveness design.

Time for a tumbler of Knob Creek...

[nts007]

Hahahahahah

Well sir to reduce wing morphing I suggest using a carbon based material with the strength greater than titanium and do not give it self awareness. And fuel tankers. Make them giant blimps

[nts007]

So how the f does the "dampner" do anything in 1". Hell it has 2 bushings so figure almost the same amount of bushing flex.

Good question. One I have pondered since I saw that stupid thing.

The only way that thing moves at all is if the axle rotates. But with a 4 link, the axle DOESN'T rotate. Depending on the link placements, there may be some very minor movement to that shock during its full suspension cycle, but I bet it is very minute.

I would like to see a go pro pointed at that darn shock under heavy use, too.

But!! By placing a shock/dampner at that point they are admitting a failure in their design to use 'their' link system to reduce axle wrap.

I've seen 3 links that don't wheel hop or axle wrap. That rear end I posted is from the Jeep Grand Cherokee. I've used it through deep snow and decent grades with sand and gravel and I've never experienced wheel hop or axle wrap. It's basically a full on 4 link with the top tied to a single joint. Which I had to replace once at 270k km. it's a 02 we've had the jeep since 06. 340k km on it and going strong. Did I mention it's been used to pull my truck outta deep snow before. Quite a few times lol

I'm just saying that this new setup is a poor design based on the fact they could have done better. And they know it hence the dampner to moderate it as much as they can

[MoparToYou]

When I was in my Power Wagon yesterday, unable to climb a simple little dirt road in 10" deep snow because of such a problem with axle wrap, I thought to myself, "the wife's Jeep would go right up this". My wife drives a 2014 Grand Cherokee that has an Eibach All Terrain lift, and 32" BFG KO2's. No lockers, just a factory limited slip, and I'll bet it would have went right up that hill that the Power Wagon failed so miserably on. Her Grand Cherokee has independent suspension at both ends, so of course no axle wrap.

True, a four link rear suspension is not supposed to have axle wrap, but the rear suspension on a Power Wagon certainly does, due to a poor design. The placement of the control arm mounts on the axle is poor, and the rubber bushings in the control arms are too big and soft. It is meant for a smooth ride on the highway, 4-wheel drive capability was clearly not the main focus of their design.

[loveracing1988]

When I was in my Power Wagon yesterday, unable to climb a simple little dirt road in 10" deep snow because of such a problem with axle wrap, I thought to myself, "the wife's Jeep would go right up this". My wife drives a 2014 Grand Cherokee that has an Eibach All Terrain lift, and 32" BFG KO2's. No lockers, just a factory limited slip, and I'll bet it would have went right up that hill that the Power Wagon failed so miserably on. Her Grand Cherokee has independent suspension at both ends, so of course no axle wrap.

True, a four link rear suspension is not supposed to have axle wrap, but the rear suspension on a Power Wagon certainly does, due to a poor design. The placement of the control arm mounts on the axle is poor, and the rubber bushings in the control arms are too big and soft. It is meant for a smooth ride on the highway, 4-wheel drive capability was clearly not the main focus of their design.

To solve all of this you need someone with a go pro plain and simple. If you saw just how rock hard the rubber bushings are front and rear you would see how little they really flex. The rubber bushings are much stiffer than any other rubber bushings other axles use.
To your other point yes I'm sure the wk2 would have made it, the 4x4 system in those things is second to none, the only other improvement would be adding a locker to the front, the rear limited slip can actually lock 100% based on conditions and the select terrain system.

[JBM Power Wagon]

I have felt the dreaded hop on my front axle of my 2011, tried wheeling once with a bunch of Jeeps, factory size tires and didn't air down in deep, packed snow. It was pitiful. I know I said it before but you really do have to air down with these trucks for snow. Once you get the right pressures it makes a WORLD of difference. I know we can all complain about what Ram did wrong with these trucks but it is VERY difficult to get a factory built wheeling rig that is great at all different kinds of conditions.

So, air down, you just have to in these trucks, especially in snow.

[olyelr]

True, a four link rear suspension is not supposed to have axle wrap, but the rear suspension on a Power Wagon certainly does, due to a poor design. The placement of the control arm mounts on the axle is poor, and the rubber bushings in the control arms are too big and soft. It is meant for a smooth ride on the highway, 4-wheel drive capability was clearly not the main focus of their design.

Are you sure it was indeed wraping, or just hopping? There really isnt a way for it to wrap... Basically just what the bushings on the control arms would allow it to move, which cant be much.

[MoparToYou]

I thought it was axle wrap. I've had that happen on a number of different vehicles that I've used in the past, some of which have been leaf sprung vehicles, and this felt the same, but with less axle movement than with leaf springs. I've also seen it in TJ and JK Wranglers, to a much lesser degree. This felt exactly the same to me. I cant imagine it was too much of the tires gripping and then slipping, and gripping again, which is what it sounds like the description of tire hop is. There wasn't enough traction to grip anything.