[Trim-man]

I'm converting a 46 chevy pu from leaf spring to install air bags in the rear. I would like to simulate the rear setup of a 70-72 chevy pu. My idea is to make "control arms" that attach at the front leaf spring hanger, then bolt the rear-end to the arms the same as you would to the leaf springs. The airbags could then be mounted between the rear and the framerails. Any reasons this wouldn't work?

 

[pro70z28]

I'm converting a 46 chevy pu from leaf spring to install air bags in the rear. I would like to simulate the rear setup of a 70-72 chevy pu. My idea is to make "control arms" that attach at the front leaf spring hanger, then bolt the rear-end to the arms the same as you would to the leaf springs. The airbags could then be mounted between the rear and the framerails. Any reasons this wouldn't work?

You'll need some sort of track locater to keep the rear end from moving side to side. Like a panhard bar, Wishbone track locater. diagonal link, etc. There would also be allot of strain on the rear end mount/control arms. The lower arms would have to be pretty beefy to handle rear end torque if they are the only means of anchoring the rear end. How about adding upper control arms similar to the early Chevelle triangulated 4 bar set-up? The triangulated design eliminates the need for a track locater. My personal opinion would be to start from scratch with a completely fresh set-up rather than adapting a partial new design to a partial old design. But that is just my opinion.

 

[Triaged]

That is NOT what you want to do. The suspension will have no way to articulate (or the body roll). The axle will ONLY go up and down.

The only way the "truck arms" on the late 60's early 70's p/u's works is because the arms are mounted to the frame very close together, are very long (to keep anti-squat down to a reasonable level) and are "I-beam" sections (which aren't stiff at all in torsion).

Truck arms are a good suspension if you copy it EXACTLY.

 

[BillyJoe]

never mind
.

 

[BillyShope]

About 4 years ago, Steve Magnante, then tech editor at Hot Rod, put together a Cad powered Chevette as an example of what could be done with very little money. He torched off the semi elliptics right behind the axle and added coils. In other words, he used the front of the leaf spring as simply a trailing arm. It's quite possible that he did NOT use a Panhard, though I can't be certain. (I looked the car over in the pits, but I just can't remember.) If you poke around the Hot Rod site, they might still have pictures available.

 

[willowbilly3]

I think that was in the April 2000 issue. I just had it laying around here a month or so ago but can't out my hands on it this morning. I know they used some Monza parts but I can't remember just how they did it now.

 

[bigbadbossman]

if you dont want to build every thing from scratch you can use the rear suspension out of a 1960 - 63 half ton chevy p/u it makes the job a lot easier

 

[cboy]

That is NOT what you want to do. The suspension will have no way to articulate (or the body roll). The axle will ONLY go up and down.

Would this be true even if you used heim rod ends or nylon bushing rod ends? I guess I don't quite understand how this setup would prevent body roll - which I understand you to say is necessary.

 

[bigbadbossman]

im sorry i should have been a little more clear about my suggestion i mearly was stating that you use the arms out of a 60 to 63 chevy to start with for the strength and modify them into a trailing arm system and use a panhard bar to control your side to side movement i have this under my truck and its working very well but to each his own

 

[Triaged]

Would this be true even if you used heim rod ends or nylon bushing rod ends? I guess I don't quite understand how this setup would prevent body roll - which I understand you to say is necessary.

The body doesn't have to roll (or the axle articulate) if you don't want it to. It might not be a bad idea for a strip only car. If you intend to drive it on the street much hitting pot holes would get old real quick...it also might shear the plug welds that hold the axle tube into the center section. If you do mount them solid to the axle tubes you won't need a track bar which would cut down on parts and weight.

If you attach the links solid to the axle for the truck to roll the axle tube would have to twist. Ford radius arm's on solid front axle 4x4's are made similar but they use a very large bushing between the arms and the axle. These take up all the twist. In fact it works like a swaybar because for the body to roll those bushings must deflect. It doesn't matter how the arms are attached to the frame...the problem is with mounting the arms solid to the axle. If you can't see why it is this way try nailing 3 pieces of 2x4's together, and "articulating" the middle one while keepin the ends of the "arms" on a table.

If you want to do something that keeps the frame mounts for the leaf springs I would try looking into f-body torque arm setups. You would use 2 links (that piviot at both ends) on the outter ends and attach the torque arm (like a ladder bar) to the center section and into a sliding mount near the tranny tailshaft.

 

[BillyShope]

Here's the latest from my warped little mind. It's only slightly related to the thread, but I don't want to start another thread for this bit of silliness.

What if the quarter elliptic leaf springs were solidly attached to BOTH the frame and the axle housing and the back end of a single upper link was also attached solidly to the housing. In other words, the only true pivot would be at the front of the upper link. Obviously, you wouln't need a Panhard. But, what particularly intrigues me is that ride height could be easily changed by adjusting the length of the upper arm. As a design consideration, the upper arm would have to be long enough to minimize pinion angle changes and its pivot point so located as to yield the desired amount of antisquat. It would be mounted slightly to the right of the driveshaft. While cornering, the springs could just be allowed to twist (as they presently do, but without the help of the rubber bushing at the eye).

(Yes, the spring would have to be custom. When compared to the more common single free end, the spring rate would be doubled, and, for a given area inertia and deflection, the stress would be doubled.)

 

[willowbilly3]

Billy, I was actually thinking what if on mounting the spring solid on both ends too. I think a link like the Monzas used that runs up beside the driveshaft to the back of the tranny. That would keep pinion angle change to a minimum during suspension travel.
I still worry about sideloading the quarter eliptics tho.

 

[Trim-man]

Thanks for all of the help guys, after careful consideration and a little assistance from RideTech, I'm going to go with the triangulated 4 link. The late model 10 bolt already has attachment points and I can use the leafspring brackets to mount the front end of the lower link.

 

[solidaxel]

Trim man, when you get started with that set up send me a picture, I think I would like to try that also on my 55 1st series

 

[evltwin]

This came up before and someone here posted this link.

http://projects10.freeservers.com/coiloverrear.html

I wish the author of the link discussed the results.