Wild horses wrap trap?

[stupidboy]

Anyone running a wrap trap from wh? If so, does it make the ride stiffer?

 

[73azbronco]

no, torque stability devices do not impart stiffness to suspension, just prevents axle rotation.

 

[stupidboy]

I just keep thinking that up and down suspension travel will be harder without a shackle to allow the axle to move rearward as the suspension is compressed. Am I overthinking?

 

[nvrstuk]

It will be hard without a shackle but you probably won't notice it with "stockish" suspension. If you have let's say 13"or more inches of travel it will be hard for a bushing to allow that much movement. I had custom durometer rated bushings made to help with movement and I experiemented a lot.

I ran similar anti-wrap bars back in the day but I always had a pivot with two spherical brgs to allow for articulation. Even with that the bushing would last about a year from the constant stresses it was under.

You really need to have some kind of anti-wrap to keep your ujoints, pinion, etc in one piece- not an option.

 

[1969]

https://www.wfoconcepts.com/i-30505470-wfo-torque-arm-kits-3-0-complete-kit-3.html#!

Another option, not bolt on by any means. But I’m a big fan of WFO.

 

[nvrstuk]

I've put together more than a few of these for fellow Bronco enthusiasts-

https://www.ruffstuffspecialties.com/R2300.html

Before I 4 linked the rear, I had a design that I built that fit over the top of the diff, 3 point attachment to the diff & housing (kept tearing the thin walled 9" housings) and max angle heim joints for not affecting articulation.

 

[Broncobowsher]

I just keep thinking that up and down suspension travel will be harder without a shackle to allow the axle to move rearward as the suspension is compressed. Am I overthinking?

You are confusing the tension link of the wrap trap with a torque arm. Very different. The whole name of the game of either is to control axle torque. With just soft springs and nothing else the issue is the torque generated from the ring and pinion countered by the traction of the tires. Simply, the axle housing wants to twist. The pinion wants to rise, a lot. The front of the leaf springs flex a lot and the spring shape goes (turn your head sideways) from a "C" to an "S". The bottom of the "S" being the front of the leaf springs.

In a torque arm that uses a shackle in front (Duff Torque Tamer for example) is a rigid arm off the axle going forward parallel to the driveshaft, or really close to parallel anyway. GM did this with the 3rd gen F-body as well. As the axle wants to twist, the arm holds it in place. As the leaf springs go up and down the pinion is kept aimed at the transfer case and any binding is released with the shackle. There may be a tiny amount of bind as the arc of the leaf spring is slightly different than the arc of the torque arm, but this is irrelevent compared to what the spring would normally flex with just light axle torque inputs. Works very well.

What the wrap trap does is very much like the old school traction bars that bolted to the top of the leaf spring via the U-bolts and the bracket that went to the top of the front leaf spring hanger. But it does it with a single link above the differential. Instead of a rigid arm that takes the torque from the housing and translates it into a lifting force on the frame it takes that torque and makes a pair of parallel compression and tension links. The leaf springs are the compression. The wrap trap is tension. As the axle housing tries to torque the top link holds it forward. The leaf springs push back. If you were to put some sort of shackle on that top link it would no longer keep the housing from rotating. The top of the housing would move back, the front of the leaf springs would flex into a negative arc (that "S" shape) and there would be no axle control added.

The torque arm just works. Doesn't matter what you have done to the rear axle, what springs and/or blocks are there. The wrap trap has more engineering in getting it set right. It also adds more forces to the springs and hangers. Whatever tension forces are on that top link, that amount of force is added to the springs and bushings pushing forward. Get into stroking and articulating the suspension, that tension rod isn't in a straight line always. A torque arm just pushes up. Articulated, it is just a side load on a shackle. Leaf spring shackles take side loads all the time.

That ruffstuff arm is a regular torque arm that functionally is like the Duff torque tamer. I was using an old stock front radius arm with a shackle on the frame bushing (was part of a tractor 3-point hitch for the pivot)

 

[rocknhorse76]

You are confusing the tension link of the wrap trap with a torque arm. Very different. The whole name of the game of either is to control axle torque. With just soft springs and nothing else the issue is the torque generated from the ring and pinion countered by the traction of the tires. Simply, the axle housing wants to twist. The pinion wants to rise, a lot. The front of the leaf springs flex a lot and the spring shape goes (turn your head sideways) from a "C" to an "S". The bottom of the "S" being the front of the leaf springs.

In a torque arm that uses a shackle in front (Duff Torque Tamer for example) is a rigid arm off the axle going forward parallel to the driveshaft, or really close to parallel anyway. GM did this with the 3rd gen F-body as well. As the axle wants to twist, the arm holds it in place. As the leaf springs go up and down the pinion is kept aimed at the transfer case and any binding is released with the shackle. There may be a tiny amount of bind as the arc of the leaf spring is slightly different than the arc of the torque arm, but this is irrelevent compared to what the spring would normally flex with just light axle torque inputs. Works very well.

What the wrap trap does is very much like the old school traction bars that bolted to the top of the leaf spring via the U-bolts and the bracket that went to the top of the front leaf spring hanger. But it does it with a single link above the differential. Instead of a rigid arm that takes the torque from the housing and translates it into a lifting force on the frame it takes that torque and makes a pair of parallel compression and tension links. The leaf springs are the compression. The wrap trap is tension. As the axle housing tries to torque the top link holds it forward. The leaf springs push back. If you were to put some sort of shackle on that top link it would no longer keep the housing from rotating. The top of the housing would move back, the front of the leaf springs would flex into a negative arc (that "S" shape) and there would be no axle control added.

The torque arm just works. Doesn't matter what you have done to the rear axle, what springs and/or blocks are there. The wrap trap has more engineering in getting it set right. It also adds more forces to the springs and hangers. Whatever tension forces are on that top link, that amount of force is added to the springs and bushings pushing forward. Get into stroking and articulating the suspension, that tension rod isn't in a straight line always. A torque arm just pushes up. Articulated, it is just a side load on a shackle. Leaf spring shackles take side loads all the time.

That ruffstuff arm is a regular torque arm that functionally is like the Duff torque tamer. I was using an old stock front radius arm with a shackle on the frame bushing (was part of a tractor 3-point hitch for the pivot)

So are you promoting or condemning the wrap trap?

 

[nvrstuk]

Disagree on a couple statements made above.

1st- The leaf springs and the torque arm do not rotate in the same arc .if they aren't the exact same length and the attachment points are not in the same plane This is one of the reasons why the bushings don't last long on vehicles with a lot of travel. Why do Broncos with leaf springs have a shackle at the rear? Why do driveshafts have collapsible splines? So when the springs actually compress the rear axle housing can move back and forth some. With a solid pc of steel (wrap trap) mounted securely at each end (try deflecting the HD polyurethane) you can see how the wrap trap can limit articulation. Try it, I've done it- it's restrictive.

2nd- the "shackle" when mounted on the front of an antiwrap bar (with a heim on each end) does a great job of keeping the pinion on the axle from rotating up & down (when designed/installed correctly) .
An anti-wrap bar WITHOUT a bushing will allow the pinion to move fwd or back a slight amount but will do the job it's designed to do by not allowing pinion to rotate or move up and down more that a slight amount because when installed properly the vertical link (I called it shackle earlier for lack of a better term) in the front between the heims is slightly off vertical. Since the bottom of the housing at the leaf spring attachment and the very top of the housing with the wrap trap attatchment point are not travelling in the same arc- the bushing is what takes the beating.

When designing and using 4 link calculators pinion angle movement is critical because even tho it is secured 100% with upper & lower links the pinion angle does change

If the upper and lower attachment points are rotating in the same arc then why is the bushing needed???

 

[rocknhorse76]

So, for us bronco owners with a limited budget, what’s the best course of action? We aren’t all rich lol.

 

[nvrstuk]

So are you promoting or condemning the wrap trap?

I think it's a great option for street rigs where the suspension isn't travelling a ton.

A great inexpensive fix so you aren't grenading joints, drivelines and pinion shafts with newer "post 1996" soft suspensions. Prior to that an EB's springs were usually not soft or flexible enought to allow the pinion to rotate that much and if they did you could use the Duff style rod's that mounted almost parallel to the spring or a typical Mr Gasket style rubber traction bar like we all used back in HS and college because they worked and were cheap!

 

[rocknhorse76]

I think it's a great option for street rigs where the suspension isn't travelling a ton.

A great inexpensive fix so you aren't grenading joints, drivelines and pinion shafts with newer "post 1996" soft suspensions. Prior to that an EB's springs were usually not soft or flexible enought to allow the pinion to rotate that much and if they did you could use the Duff style rod's that mounted almost parallel to the spring or a typical Mr Gasket style rubber traction bar like we all used back in HS and college because they worked and were cheap!

This is why I can’t afford to wheel with you Brian

 

[73azbronco]

So, for us bronco owners with a limited budget, what’s the best course of action? We aren’t all rich lol.

How much HP? I'd say less than 300 and you really need not worry about torque.

I have the version of ruff stuffs anti torque device, torque control. No way it binds once set right.

 

[rocknhorse76]

How much HP? I'd say less than 300 and you really need not worry about torque.

I have the version of ruff stuffs anti torque device, torque control. No way it binds once set right.

Does anybody actually build engines with less than 300hp these days?

 

[73azbronco]

Does anybody actually build engines with less than 300hp these days?

Well, most popular appears to be the venerable explorer 5.0, so yeah? But, me? Nooooooooo.

 

[rocknhorse76]

Well, most popular appears to be the venerable explorer 5.0, so yeah? But, me? Nooooooooo.

Haha me neither. Mine is more of a budget build though.

 

[stupidboy]

Where was all this discussion before I started installing this yesterday.

 

[rocknhorse76]

Where was all this discussion before I started installing this yesterday.

What will the primary use of your bronco be? If it’s mainly street with occasional gravel roads, what you have will be fine.

How much HP? I'd say less than 300 and you really need not worry about torque.

I have the version of ruff stuffs anti torque device, torque control. No way it binds once set right.

I have a fairly healthy 408W, 4R70W, Blackbox Titan, NP205, and tons with 5.13’s. I’d say I have concerns with torque lol. I also have both the Duff Torque Tamer and Ruff Stuff anti wrap setups sitting in my garage. I’m just running out of real estate to mount either of them, which is why I might end up linking the rear.

 

[nvrstuk]

So are you promoting or condemning the wrap trap?

I think it's a great but like I mentioned earlier, only on vehciles with "limited" suspension movement. The RS setup works great for stopping rear end rotation or wrap as we have called it for long travel suspensions.

Like Broncobowsher said above, GM used something similar on their F body cars. I am building one similar to those for use as a 3rd link on my Shorty build but Shorty like all F body cars has very limited vertical travel and that's why it works so well. He was also spot on about leaf springs turning into an S shape when torque is applied. Took me a long time to realize that's why I kept breaking rear springs. Also used to snap rear leaf spring hangars almost every year. Compression and tension forces on the rear end is pretty amazing.

TS posted up about the leaf springs essentially being twisted into an S and being the bottom "link" about 20 yrs ago and that was my clue as to what was going on with my broken leaf springs every few years.

 

[Broncobowsher]

Disagree on a couple statements made above.

1st- The leaf springs and the torque arm do not rotate in the same arc .if they aren't the exact same length and the attachment points are not in the same plane This is one of the reasons why the bushings don't last long on vehicles with a lot of travel. Why do Broncos with leaf springs have a shackle at the rear? Why do driveshafts have collapsible splines? So when the springs actually compress the rear axle housing can move back and forth some. With a solid pc of steel (wrap trap) mounted securely at each end (try deflecting the HD polyurethane) you can see how the wrap trap can limit articulation. Try it, I've done it- it's restrictive.

2nd- the "shackle" when mounted on the front of an antiwrap bar (with a heim on each end) does a great job of keeping the pinion on the axle from rotating up & down (when designed/installed correctly) .
An anti-wrap bar WITHOUT a bushing will allow the pinion to move fwd or back a slight amount but will do the job it's designed to do by not allowing pinion to rotate or move up and down more that a slight amount because when installed properly the vertical link (I called it shackle earlier for lack of a better term) in the front between the heims is slightly off vertical. Since the bottom of the housing at the leaf spring attachment and the very top of the housing with the wrap trap attatchment point are not travelling in the same arc- the bushing is what takes the beating.

When designing and using 4 link calculators pinion angle movement is critical because even tho it is secured 100% with upper & lower links the pinion angle does change

If the upper and lower attachment points are rotating in the same arc then why is the bushing needed???

I think there is a little mis-communication. The shackle (something to allow the small amount of for/aft travel) is needed with the torque arm.
The wrap trap is not an arm, it is a link. That can't have a shackle. It works by limiting for/aft travel.
My comments about not having a shackle are in reference to stupidboy's question about a shackle limiting suspension while he is inquiring about the wrap trap.
Only the wrap trap should NOT have a shackle.
The ruff stuff or Duff style arms SHOULD have a shackle.

More boring history stuff. Back when vehicles had torque tubes (before exposed driveshafts) the rear axle had a torque arm that pivoted off a ball around the single U-joint at the back of the transmission. This is very much like the torque arms. The leaf springs (when used a pair of parrallel springs and not a single transverse spring) would have shackles at front and back. This was because the pivot and thrust for the rear axle were at the back of the transmission. A solid hanger would bind. When open drivelines (What we think is normal today, driveshaft with 2 U-joint locations and telescopes) came to scene the front shackle on the leaf spring changed to a simple spring hanger. The axle forces now go to the frame instead of the back of the transmission. The only thing that still uses the old school torque tube design (that I know of) is spring cars. They do away with the transmission and just a direct drive to the back of the engine with a sliding in/out engagment. I find it amazing how much modern sprint cars have in common with cars from the 30s.

As for the wrap trap. The only OEM application I know of for this design goes back to the late 60's AMC. They used a pair instead of a single. But they were traction bars on the higher power AMX and Javelins. Top of the axle pull link.

The torque arm goes back to the '60s and can be seen as an evolution of the pinion snubber. A rubber bump stop added to the front of the pinion that would hit the floor pan on hard acceleration to prevent pinion rise from the spring wrap. The off-road world just grew it out to a much longer arm and captured the front of the arm in a pivoting shackle arrangement instead of a rubber bumpstop smacking the floor. We have too much wheel travel for the floor smacking snubber to work.

I've had thoughts of using a limit strap like the wrap trap. Top of the axle housing to the frame. Under acceleration it would pull tight.