Customs Truck arm suspension swap with guidance and criticism

I know there is quite a bit of info on this , but it still seems to be lacking in some places. I know there are pros and cons to this swap ,but these are the parts I have and it was practically free so it’s what I would like to use.
I am planning on the swap in my 54 Chevy. My leaf springs have given out…they actually invert around a turn and the bang scared the hell out of me when it happened. So it’s time for a new rear suspension which I was considering anyway.
I have the c10 cross member, arms , axle bolts (will buy new ones eventually), new saddles and everything off the back of the c10 including springs.
I had to section the cross member a few inches to fit under the car and I’m pretty happy with how it will fit and the approximate location.
the rear axle is the next dilemma. I have an s10 axle and the problem I am realizing is it is a 1/2” smaller in diameter (2-12”) than the c10 axle (3”)
I am thinking of getting some 2-1/2” inside diameter tubing with a 3” outside diameter and welding it to the axle where it will mate to the saddles and truck arm.
I’m also going back and forth with welding the crossmember in or welding on some brackets to the frame to bolt it in.
I would love to know what some of the more experienced fabricators and rudders think of the plan or if I should drop back and punt.

 

It would be a whole lot easier to just buy some new leaf springs and bolt the new rear end to them. With the truck arms you need upper and lower spring pockets also to fab. I don't see you gaining much with the truck arms over new leaf springs.

 

I put truck arms under my 54 Studebaker Conestoga (wagon) to hold the Quick Change in.
I put a wishbone in for centering, coil overs on it to hold everything up and attached a new anti-sway bar in there too.



Mike

 

Truck arms were never a performance-driven design. They were a cost/production-process-driven design. They weren't meant to do a better job, but the same job cheaper.

What we've got is basically a wishbone setup, but an imperfect one because the "ball" is separated into two pivot points. The only way to get that to halfway work is to introduce torsional flexibility in the arms and compliance at the axle mountings. It feels compromised and inelegant to me.

You can complete the wishbone using a Johnny Joint or something if you like, provided there is physical room for it above or below the driveshaft. That isn't to say you'd always want to do that. For starters it's likely to place the pitch (launch) instant centre a bit low for a strong hook, even if there is room to put the pivot point above the driveshaft.

 

Someone suggested I do that to my 53. I kindly asked him to get out of my garage. He had a C 10 and his whole world revolved around C10. I stated “you ain’t making a C10 out of my car. To make a long story longer, his whole family had C10’s. Anyway after seeing some of the aftermarket trailing arms at the Turlock swap meet, damn that is actually a neat setup. I owned a 63 suburban for years. Free and if you’re changing your engine, transmission, go for it.

 

What fun would that be. lol

 

They reverse arch when cornering then pop back?

I didn't know that was possible.

 

Why did/does NASCAR use them- seams the trailing arms work the best for them ?

 

It was a crazy noise, but I had me and a buddy jump on the bumper (under 400 lbs) and the loud bang came again.
I was going a bit crazy for a while checking body bolts, trans, engine. I didn’t believe they could reverse but they did.

 

The truck arms are a good option for cars with rear coil springs like my Buicks. I had to shorten mine 3" to work. As far as your questions, a split piece of pipe as you describe to make a saddle will work fine. Supporting the rear of the arms will necessitate making chassis spring pockets or using coil-overs with fabricated brackets like Mike did. This is not my design but is a good option for mounting the arms in the front or something similar to this.

 

NASCAR. It's the rules. 3 link was legal too. That is until my 3 link NASCAR North GN cars ran circles around the neandithal truck arm cars. Ricky Craven. 10 features 1991. Whipped every Southern driver that came North. 3 link rear outlawed during the winter. Only truck arms allowed. Bounce off the wall and the rear end stays with the car. Minimum clean up. One of the reasons. The other is keep all cars identical.

 

The other issue is the s10 rear end. If the axle tubes are too small, why use it?

 

The stock arms are designed to be able to twist.
IIRC, they are a pair of C channels welded together, to create an i-beam.

If people substitute square tube, that would create a bind.

 

Way back, it was common to use truck parts for durability.

 

It’s what I have. If people don’t think welding tubing to add to the diameter is a good idea I will try to locate an explorer rear end that is bigger. I am just trying to do this with everything I have and save as much as I can. The s10 rear is part of all of the stuff I had

 

I think what you're doing, and the plan is just fine. Stay the course and move on. You might think about Coilovers in place of shocks to do both jobs. Been there done that and things worked out just fine. Weld in the crossmember and never look back.

 

There should be 2 1/2" spring perches and u bolts available to fit the s-10 axle diameter, then drill a new holes to fit the smaller u bolt spread

 

Why would you muck around with such hack-together nonsense? Just get the proper sized saddles and u-bolts. This isn't rocket science.

 

3" round 1/4" wall tubing is exactly what I would do.
If you diagonal cut 2 pieces of tubing at the same angle as the truck arms it would look almost factory
split the tube pieces so it wraps 360° around the tubes and weld them. [just be careful with the heat]

A tubing "spacer" is no worse than 4-link brackets that are welded to axle tubes.

Truck arms are not the ideal suspension with more modern alternatives BUT they are a simple compromise that is reliable and a DIYer generally can't go wrong.
Just get the ride height as desired and check the pinion angle [and rear end is correct clearance left to right] before you do the final welding.


Also
That bang you hear sounds like shackles trying to invert when the suspension is extended [this happens a lot on tandem trailers with brakes on the rear axle when the trailer is empty]
A simple fix is limiting bars welded across the shackles.

 

That would be normal common sense thinking.
But truck-arm suspension is made for trucks [which have larger diameter axle tubing] so offset axle pads might not be available for 2-1/2" tubes.
If they are available it would be a no brainer.

Adding 1/4" wall tubing to the outside would actually restore the distance of the pad to the axle centerline.

If you ever read an old Chrysler Direct connection book on their suspension. They clamped tubing around the axle tubes to "float" the axle for their "leaf link" suspension.
A properly welded spacer done to a good workmanship standard would be a perfectly acceptable compromise [I've seen a shitload worse on race cars]

Edit: Ford 8.8 rear is a common swap into a 4th Gen Camaro.
They weld the Camaro axle tubes into the Ford 8.8 Rear ,they are a slip fit
[this avoids fabricating brackets etc]


Welding spacer tubes for truck arms would be a lot easier than this ^

 

The 28/30 something Chevy rear end that I have sitting out back has a similar setup but has a torque tube. The axle rides in bushings that are part of the mount on the leaf spring.

A Truck arm rear suspension has been one of the considerations for my 48 since I have the rear half of the chassis a 70 C 10 that I used to have that I could salvage the suspension from.

Other than that all I have to say is some times you have to run what you have on hand rather than spend big bucks for something (new leaf springs) just to make a few "you shouldn't do that" guys happy.

 

Something to think about. If you don't have a friend in the pipe trades, 3" DOM tube with a 1/4" wall is EXPENSIVE. $12.80 per inch.



Sch. 80 pipe comes close, but not quite what you would want.

 

I’m not sure that’s possible, The arms are set for the u bolt size from the larger diameter axle. The arms are two channels welded together and holes are formed in the channels for the u bolts. It might be possible I guess ,but might actually be more work than just welding some tubing around the axle.

 

I actually have 16” of it I picked up on eBay for about $25. I just want to make sure this is a good option before I started.

 

That bang scared the hell out of me. The car was used quite a bit and had new leaf springs put on for about 2000 miles. Then I decided to chop it and life got in the way and it sat for about 12 years … after the chop the first drive did the bang and I can definitely say it was nerve racking.

 

Well that eliminates my thought that some kid in the early had run long shackles on the back to raise the rear end for that raked look and screwed up the rear springs.

 

It is a perfectly acceptable modification .

I have used slip joints [both internal and external] to shorten axle tubes , And to shorten trailer axles.
You are only using the tubing to adapt 2 different sizes.[it isn't really that structural]

It is up to you to do this to a reasonable standard of workmanship . If your welding isn't up to a decent standard ,then plug /spot weld it to set it up and get somebody else to weld it.



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This is how a trailer axle is shortened [they do it on each end because the axle is cambered]

 

If you're actually a Welder and not just a welding machine operator none of this is a big deal.

 

I have done a few parallel 4 bars and a mustang II, but not a suspension like this.
Every thing is still together on them. I’m not looking to mess it up on this one

 

Drill new holes through the arms and weld in a sleeve. Pretty simple.

Welding on the axle tubes is likely induce a bend that you'll need to straighten out. Lot more possibility for screw-up there.