One other thing bothers me:

While the illustrations of our suspension and frame look very accurate, my axle mounts to the springs are making the pumpkin level - not with the pinion tilted up like in the diagram. Is my truck screwed up, or is the drawing?

 

Just a thought.

If you want to see exactly what your suspension is doing, video is a good thing. Video while moving is often shaky and difficult to arrange, but....

What about setting up a stationary camera on a tripod and running your truck on a dyno?

Not sure it is worth its own trip to the dyno, but it could certainly show flex and twist in the rear end setup

 

I'm still trying not to hijack corksil's thread. I'd like to get all the static issues and the traction bar theories addressed, because this would be in support of his (and my) questions. Once those are answered, I can move on to solving the Stinky questions in my own thread.

 

Depends on the type of rear driveshaft joints. With ujoint said you want between 1 &3 degrees with 2* being the target.

You want the transmission -2* and the pinion +2* at ride height, this cancels out the ujoint harmonics. Don't forget to make sure your slip yoke is installed correctly so the joint are in phase as that gives off a undesirable frequency.

If you have a CV joint at the transmission end you can point the pinion directly at the trans output. At ride height.

 

If you are going to crawl under your truck and check angles with a angle finder , take a jack with you and carefully apply some pressure to the transport see if the rear tranny mount is shot. If the rear tranny mount is allowing the trans to move more then spec it will throw off the driveshaft angle that cancels out the ujoint harmonics.

 

The gravity analog angle finders are accurate enough for this job but I like my digital one.
Use the frame as a zero reference to compensate for tire inflation, park job, ect.

 

Tug,

I recall reading your truck has been involved in a accident and you have had some vibration or suspension issues ?

You should also measure side to side and verify your drivetrain is still mounted squarely in the chassis. A single degree of shift sideways or cocked can produce noticeable harmonics. If you suspect things are not square I would would start at an alignment shop and get a 4 wheel alignment, if that is out of spec, depending on how far out it is you could go to a collision repair place and have it put in a chassis jig to get straightened and or find the bent parts.

 

All of the accident repair stuff was done long ago - before this problem started. Laser-aligned frame, 4-wheel alignment, no uneven tire wear, very straight tracking... good stuff there.

I'd start my own thread, but it was a trollfest last time. I'll just learn what I can with corksil's thread and sort it out.

That diagram was excellent... that's the stuff I'm looking for.

I hope corksil is still with us.

 

Yeah I just read through page five. Seems I spend so much time working on this truck that I am it's slave. I spend more time reading/researching/working-on-it than I do driving it. It's growing very tiresome.

Luckily tugly has more enthusiasm than I, so thanks to him this thread is still going.

I'll be sure to call OUO before ordering any traction bars but I'm leaning more toward purchasing one of their kits instead of trying to fabricate my own.

Time for me to go tear apart the rear parking brakes.... for the third time. New rotors and p-brake cable lever actuators this time. Every other component in the entire parking brake system is brand new. Frustrating to spend so much time and money on a truck that just doesn't ever seem to work right. Anyways, I digress.

Yeah, I'm still here. Wish my mind wasn't still on this, but it is.

 

With these trucks: Some days you are the hammer and some days you are the nail.

Every one of us, that do our own work, knows what it feels like to be the nail for a day, a week, or a month.

A long spell of the hammer days is coming soon...and that makes it worth it......

 

I was the nail for three years - upgrading to more power will do that to you. After a trip across the state for the holidays, I was so fed up that I threw the keys in the cupboard and left them there for 6 months, while I contemplated how much Buck$Zooka ammo I can get back by parting out the truck. After my good mad had wore off, I came back to it with a rested perspective. I finally nailed down everything under the hood in short order (amazing what walking away does for the perspective). All I have left is a vibration under there (it feels like the driveline). I took a video of the back suspension while driving, and I now feel the ladder bars are just fine the way they are. I suspect the only suspension issue I may have left are the sagging front springs.

corksil - After all my experiences and observations, I feel pirate4x4_camo brings an incredible wealth of information to this thread. Saying that, I suggest you keep your eye on the goals of your suspension. It's easy to get wrapped up in the proper way of doing things (speaking as the emissary for all of OCDdome), but when it comes to a pavement prancer - we can fudge things a bit.

I looked hard at the OUO Bolt-On Traction Bars w/U-Bolt Flip [LINK], it looks like a very sound design with excellent quality materials. It also looks crazy-easy to install. The caveat is that's not the ultimate price listed in the window there - you still need to buy the square U-bolts.

 

Apparently I'm not the only one pursuing automotive perfection.

Regardless, I called OUO and spoke to jared a few times and he recommended their simple bolt on kit with adjustable length.

Here's my understanding. They used to sell fixed length bars, and some websites still list them for sale -- but they never sold in any sizeable quantity so they have more or less be phased out and discontinued. The advantage to adjustable length is that they can be lengthened at a later point in time to account for proper geometry with a lift, taller tires/blocks etc.

Adjustable length comprises 99% of the kits sold by OUO.

Also stated, was that short gusset are for typical setups -- large gusset are more so for highly lifted trucks with very tall tires. Larger gussets will slightly degrade ground clearance at their attachment point to the axle, but are a little more for show on a very tall truck and don't have much of a performance gain from short gusset traction bars.

Also gleaned that the bolt on simple kit is best for a hauling/functionality application -- as it was stated that the u-bolt flip kit was designed to address issues inherent to the 2004-11' F-series suspension design.

With that said I asked if there were any reports of the bolt on kit twisting/slipping on the axle tube under extreme force and was told that due to the design, it's not possible because the axle mounts would hit the blocks and the ubolts holding the blocks and springs would have to spin on the axle tube as well.

After looking at the picture and thinking about this again, I'm not sure it's the case because if the pinion were to rise in the front under hard acceleration, the traction bars would try to rotate on the axle tube in the downward direction, not up toward the blocks.

Either way, I plan on ordering the simple bolt on kit in the coming days.

Take a look and try to visualize what might happen under severe acceleration with 20k pounds on the rear hitch. Maybe you'll come up with something different than I did from an engineering standpoint.

 

Also mentioned was that drilling the frame for the front mounts is inevitable -- but weakening it due to the holes was negligible in terms of strength due to the "location."

Also worth adding that I was told the traction block kit was primarily designed for lifting a vehicle as well as stabilizing the rear axle. I have no plans to lift the truck, and was told that the traction block kit would not serve as any real upgrade justifiable for the cost increase.

As for weld-on vs bolt-on, there's a $280 difference in cost -- I'm not sure how many proficient welders you know, but maybe the bolt on kit is a better option as a broken axle tube/axles/differential/carrier-bearing and loose drive shaft and destroyed transfer case and replacement pickup bed might cost if the welds don't hold. That decision is up to you.

 

Corksil, this is the same kit I plan to go with from OUO when I can save up enough pennies. Keep us posted on the install and the results when you get them.

As for their performance, I have 100% confidence that they do what they were designed to do because OUO is a reputable company that stands behind their product and service. I don't fully understand all of this suspension stuff going on while traveling down the road, but that is what the experts like OUO are there for.

Keep us up to date and post pictures!

 

I have been visualizing this for weeks, and it took me a while to digest the opposing forces at play. The "rules":

• The axle mounting block will always be parallel with the springs.
• If the forward springs try to flex up with torque, the length of the traction bars won't let the axle move forward to allow the twisting. Any twisting of the springs has to involve moving the whole axle forward or backward in relation to the frame.
• When the springs compress with a load, the traction bar mounts pivot to allow the axle to maintain its natural angle in relation to the frame.

On a drawing of the springs, draw a straight line between the rear and front eyes of the rear springs. Attach the axle to this line, below the springs. Envision a twist in the line with the axle attached - you will see the axle try to go forward or aft in relation to the eyes.

All we need...
A: Prevent forward or rearward movement of the axle.
B: Allow the axle to rise and fall perpendicular to the spring eyes, without trying to twist it.