Torque arm mount

[jaybee]

Here's something I'm kicking around in Paint for mounting a torque arm to a Ford 8.8" rear. Any issues?

• Use leaf spring saddles to bolt the assembly to the axle tubes.
• Set driveline angles before welding the spring saddles in place, just like with leaf springs.
• Wedges can be used to make minor changes in driveline angles if needed.
• The goal is to provide maximum beam strength all the way to the axle tubes.
• Bolt through the holes in the strengthening ribs to fully stabilize.
• Connect the axle tube mounts on each side with a cross tube under the nose of the diff case.
• Torque arm proceeds forward from there.

[kb426]

The crown vic and the mustang I believe both have large bosses on the center section. If there is a way to use them, that would be my 1st choice. If not, the tubes need to be completely welded to the housing. They are known to come loose in high hp. applications. The holes on the side of the pinion are where a balance weight goes on some models. That could be used for additional bracing. Is your thought to run the torque arm parallel to the driveshaft or lower than it?

[jaybee]

Good information. I've heard the tubes don't always stay firmly in place with high horsepower. I'm thinking the torque arm would run just beneath the driveshaft, as they work best right down the centerline. It could go beside it if the chassis can accept an off center driveshaft like a stock Ranger.

[enjenjo]

A lot of this depends on what the rest of the suspension elements are. I have had good success with a torque arm biased to the right and a pair of lower control arms on each side similar to a third gen Camaro. This setup does require a Panhard bar or Watts linkage to control side to side movement.

I made the torque arm from 1" tubing in a tapered Girder configuration similar to a ladder bar, but longer, and with a bend towards the driveshaft and  down to clear the floor. The back end is fastened to the housing on a batwing welded to the axle tube and the end of the center section to strengthen that joint. You could use a similar batwing on the left side and incorporate using the holes in the front flanges to stabilize the center section, but I never found it necessary. The front of the arm was mounted to a large compliant Urethane mount in the Xmember but alternate mountings are possible as necessary.

I can do some sketches if you like.

[jaybee]

"I can do some sketches if you like."

Yeah, I'd love to see that, actually.

To go along with this I have a picture in my head of replacing the leaf springs with a set of rectangular tubes with end caps. They would be probably taller than the spring pack so as also to serve as lowering blocks. The left and right links would come off the front of those blocks, positioned so as to be level, of course.  The axle end of the panhard bar would attach to the back of one. Coilovers would obviously take the place of the shocks on the existing clamp plates. In most cars that's going to require the trunk floor to be reinforced or a bar to be run across the frame rails for top mounts.

[kb426]

I walked by the crown vic rear in the yard. It doesn't have the upper bosses on the center section that the 96 mustang had. However, the coil spring mounts are welded to the tubes and would be substantial to bolt brackets over.

[enjenjo]

Here are some crude sketches of what I made. My hands were not working well today. The arm material was 1" round tubing. I believe the front bushings have an ID of 1 1/4" The links on the back are just clevises. This is a link to what I used for the front bushing  https://www.amazon.com/Prothane-6-1207-BL-Black-Radius-Bushing/dp/B00387XUOK

The piece coming off the bottom of the lower drawing is for a brace from the hole drilled in the front flange.

I have more work to do on the picture

In the meantime you can watch this video 

[jaybee]

That's significant. However you mount it, the axle end of the torque arm is going to be a high stress area.  It's like the business end of a pry bar...a lever 3-3 1/2' long. The mounts had better be able to handle it.

[enjenjo]

I was not overly impressed with his design, but apparently the center section can be welded with stainless steel rod.

[jaybee]

Thanks for your thoughts, Frank. I hadn't considered radius arm bushings. They're big and they're intended to flex, which makes them perfect. I as thinking perhaps a 1" or larger sway bar bushing, probably held in something more like a pillow block than the steel strap that usually retains them. My concern with that has been that there may not be enough thickness in the urethane to properly deal with the vertical pivoting within the bushing.

[jaybee]

"I was not overly impressed with his design, but apparently the center section can be welded with stainless steel rod."

Do you mean in the YouTube video? I can't seem to get it to play, so I'm not sure what he's done.

[kb426]

I haven't been able to get videos to play since the last update. I had been leaving a channel name to link to the suggested video.

[jaybee]

The more I look at them the more I think Ford radius arm bushings are perfect for the application. They're compliant in a longitudinal direction, which allows for the differing arcs of the torque arm and the side links of a torque arm suspension. The pickup truck radius arms have to pivot slightly along their length as the twin I beams move up and down, just like suspension articulation of a solid axle rear suspension. The central part of the bushing assembly has a limited thickness of rubber, giving it a pretty solid "hit" when the torque arm restrains acceleration and braking torque.

A lot of these suspensions use heim joints with a slider. That's a lot of metal on metal movement for street cars. Another alternative is a dog bone link, but that can be a packaging issue.

[kb426]

I'm in agreement in the polyurethane bushing part. When I built the 32, the cheaper parts were solid mount. The ones I used had rubber bushings in the radius rods. 12 years and almost 40,000 miles later, they were as they should be.

[jaybee]

Here's the torque arm installation sold by RSS for Falcon-chassis Fords. As an Australian company you know it's been subjected to some engineering confirmation. I think you could do something similar but configured differently to bolt to a Camaro subframe, thought it would have to bolt to the inside and bottom of the subframe and probably involve a pass through for the exhaust. Mopars would be tough. I think with Mopars you're looking at subframe connectors. There's nothing in that part of the car strong enough to attach to. Seems like the crossmember in the picture could benefit from some attachment to the floor at the edges of the tunnel, in much the same way convertibles had seat pans bridged by a plate to stiffen the car.

The RSS stuff brags about being bolt in, but in some ways that makes it overly complicated.

A full frame car or truck...that's a different matter, obviously. You've got frame rails, just put the crossmember where you want it.