These videos helped me make a final decision.

https://www.youtube.com/watch?v=PYm_...ature=youtu.be

https://www.youtube.com/watch?v=nuQX...ature=youtu.be

https://www.youtube.com/watch?v=k3h9...ature=youtu.be

 

You got it. We could go more in depth on the tech behind the single vs dual bars but those are good generalities.

 

If your bars do not have a pivot or shackle on the frame end then I can totally see this happening. I bet if you go adjust them so they are not in tension at ride height your mystery vibration will mysterisly disappear

 

Just curioous , what was your final decision ? What did those videos reveal to you ?

 

My final decision (which I have not acted upon yet because that is a lot of cash to drop right now) is that I would certainly benefit from traction bars when towing my travel trailer. I am not dead set on OUO, but from what I have seen they have a very good product and that I am confident I would not have to do the modification again anytime soon if/when I went with OUO.

Since installed the Roadmaster Active Suspension on the truck in my signature, I have eliminated the axle wrap when unloaded. Although, strap my 10K lbs travel trailer to the truck and (albeit much better since installing RAS) the axle wrap is back. My WD hitch is set up properly because I only get 1" drop in the rear and no drop or rise in the front of the truck.

I like that the OUO can be adapted to mount to the frame where it is feasible for the specific truck they are being mounted to.

 

Hopefully I'm not hijacking, but here's my thing:

I have traction bars, and I'll vouch for their effectiveness on our trucks, even if they're just chipped - or stock with tired springs. It is a night and day difference, and Stinky will never be without traction bars (in one form or another) again. The bars immediately made shifts so much smoother, and I can really feel the difference in control back there. I had a visit from a member not long ago and he took Stinky out for a test drive. He immediately felt the difference in the rear, and now he wants traction bars on his rig.

That being said... there is a shudder back there under the right conditions. After all my research and observation, I am convinced the shudder back there is from the traction bars binding. It took a long time to sort this out because of the number of other issues causing a mish-mash of vibrations and shakes. I have since solved all of the vibration and shake issues, and the binding shudder popped up as being obvious after all the masking was gone.

I have a plan to solve this, but it's not cheap... neither was the first "solution" that is now a suspected fail. I've scoured the internet, looking for animations of how each traction bar design works - and there are a gagillion designs. Unfortunately, I've found only a handful of animations to demonstrate the interactions of all the suspension parts - and none of those show the complete picture.

I understand the forces at play, I'm pretty good at envisioning the lever actions that take place with traction bars - and I can see the potential for damage to a bunch of pieces strewn about under the truck in a haphazard way.

Using corksil's very good list, here's where my brain goes, and I invite counterpoints:

-solid non-pivot mount to rear axle to control pinion rise/fall

A ladder bar with the mount welded to the axle will force the pinion to rotate with spring compression - unless the front connection can rise and fall at the same angle in relation to the springs. This is where the traction bar may have better action, if the front mount is in the correct location.

-traction bar length and angle matching driveshaft

This one took some thought. The length to the middle U-joint? To the carrier bearing? As I play this through my mind, I see where the front pivot of the traction bar needs to be at the center of the arc of the rear axle movement during compression. Remember... compression causes the axle to rise and move aft in relation to the frame.

-shackle between forward traction bar mount and frame to allow suspension articulation

This gets very weird: The shackle would allow fore/aft movement and no real rise/fall. This works on ladder bars, but not on single traction bars.

Because of the fixed front spring pivot and floating rear spring shackle, the choices are to keep the pinion one angle with traction bars, or have the pinion rotate about the arc of the front connection on ladder bars.

My existing system is ladder-bar-ish with no shackle - and the front pivot is installed too far back.

 

I have heard people refer to the RAS before but never bothered to go look at it until now. ( I will reserve my opinion and stick with the facts )

The RAS is equivalent to a anti wrap leaf in your spring pack. A anti wrap leaf is simply a half of a leaf spring, or a leaf that only goes from one eye to the center pin. This gives the spring pack an asmetrical rate or put another way, doesn't increase the spring rate that affects ride quality but adds spring rate to half of the spring to resist spring wrap under acceleration or braking depending on which end of the spring you put the 1/2 leaf.

You say your axle wrap is back, watching those videos I would say the guy in the video without the traction bar would be perfectly fine without one. Did the axle wrap a bit in the video ? Yes of course it did but it did so as it was designed to and didn't look to have any ill effects on the handling. It should be noted the driver was doing a smoky burnout in the truck to get the axle to twist and it really didn't move very much. ( I am sure if you are not familiar with how much movement a axle has it looks drastic and this of course helps sell products to eliminate things that likely do not need to be elimanated )

Before you go and add a second anti wrap device to your spring pack let's dissuss your axle wrap issue.
When are you experiencing it and what effect is it having on your trucks handeling ?

 

On the note about the TB matching the driveline angle, I'm thinking what is more in play is the arc the housing takes in compression/extension and this is determined by the angle int he leaf spring and the swing of the shackle. I don't think it's critical to match to the driveline for this reason. Controlling pinion rotation is much more so.

 

Single bar, as close to the pumpkin as possable, and as long as possible , with a shackle on the "frame" end(build a crossmember) and call it a day. Best axle wrap control with least amount of affect on suspension movement. I like to weld the axle brackets on. Usually part of it goes on pumpkin and part on tube to tie the two together better, just for piece of mind to keep pumkin from spinning on tubes.

 

Dave, got a pic of your setup?

Stewart

 

Tug

Brotha I think you have something else going on in your rear suspension besides a lack of traction. If you are putting enough torque to the ground to spin your tires thus loosing traction then I suspect you have more then just a chip. I would tend to agree with your assessment of the shudder being caused by a poorly designed traction bar or anti wrap device.

Start at the beginning, what was the rear axle doing that made you start adding devices in the first place ?

Final thought ( at least for this post ). You seem to grasp the basic guidelines and are wanting to understand the geometry that is at play. Building a simple model can help you visualize this. Legos, Popsicle sticks pvc pipe. Anything can work.

 

Stinkys butt got a kiss in a parking lot

 

Thank you all for contributing.

I would like to reiterate that the reason I started this thread in the first place is because I use the truck for towing heavy loads. This truck is not a daily driver -- it is a work vehicle and only used for hauling.

full trailer

14000

My primary concern is keeping the rear axle as close to the middle of it's acceptable range of travel while accelerating aggressively in 2wd Low, First, and Second gear on pavement.

I'm not doing burnouts, or trying to race the truck. All I'm trying to do is keep the truck from tearing itself apart when accelerating with a heavy payload from a dead stop.

 

please define which travel range. Are you talking about the wheel traveling up and down in the wheel well, Forward and backwards in the wheel well or the axle housing twisting ?

Each of those ranges of travel can be controlled but the reason you have wheel travel is to accommodate different operating parameters, keeping the wheels in the center of any of those 3 ranges is not really nessasary and is designed Ito the system for short periods during acceleration. As long as you are not exceeding the travel limits you should be fine, I would be more concerned about setting up the ride height for extended operation and let the travel do its thing.

 

A bit more than just a chip...




Bending the driveline, spinning the pinion bearing, damaging the U-joint....

That's next. I even thought about downloading "Crayon Physics" and playing with that.

While my picture may indicate otherwise, that was my very first full-on test with max power (which I have never used since). After trying to break Stinky in half, I focused on what could be done to prevent the ol' Stinky-drag-his-butt-across-the-asphalt maneuver. The forces at play during my test and available to me in the Tow tune are not all that different than what you face when towing heavy - but you have spring compression to assist with keeping the front of the spring down. The RAS may be all you need in your situation, but that could be a half-"S" approach.