ive read alot of 8.5 threads and this is one of the more popular topics, but here goes my idea. ive been thinking, as being kind of new the f-bodys. i have owned several in the past, but ive got one all tore apart and want to upgrade the rear axle with out a upgraded bank acct. anyway, as i see it the problem is with a axle swap, is mounting the torque arm to the center section. but i wonder if maybe if a guy could fab up a ladder bar that could wrap around one of the axle tube right next to the center section and run it all the way farward to the back of the trans where the original setup is at. i havnt put too much thought in how to attach the front of it, but think the setup part at the axle might be a good idea. the truck style ladder bars just bolt around the axle tube, but figure out the correct pinion angle and weld it in. ive got a 383 in the mix, so im not gonna be putting down crazy numbers, but i dont want to put 800$ into a 7.5 or pony up for the 12. am in not affraid of running the welder, and my bud just bought a plasma machine. i think im just crazy enough to try it! what do yall think?

 

There are guys who run ladder bars, sure, but there's a reason it's not popular on the street cars. It doesn't work well for fast corners, or so I have been led to believe.

The key is getting a torque arm to work. You'll have to fabricate a plate to mount the torque arm to or use your plate to hook up a pinion snubber type mount that goes slightly forward and mounts to the body.

I'm working on making a plate to do that for my firebird. It's really labor intensive, but I have more time than money.

First you have to cut the center out of a plate that will allow it to slide over the front of the axle where the pinion sets on. This is the hard part because you have to keep trimming with the torch until it really "fits" the ribs in the housing. Then you need a plate on each side welded to each axle tube. This set of 3 plates welded together will give you a stable place to weld your torque arm mount to. Then you can mount a torque arm.

It's on hold for me right now, but it's going to help me put another rear in my firebird. It's just an idea, so I don't have any pictures yet. Maybe it will give you a place to start from.

 

He doesn't want to install ladder bars, he wants to use one ladder bar like a torque arm.

That won't work. You can't position it close enough to the center of the diff to line up with the back of the transmission. If it's off center, it will cause suspension alignment problems.

I had ladder bars in my race car as a way to install a 9" without a torque arm. Although you can drive on the street with ladder bars, you probably won't like the handling.

As I tell every one else who doesn't think the cost of a diff upgrade is worth it. Drive what you have until it breaks. The 7.5" is stronger than most people give it credit for. If you manage to break it, then decide if $2500 for a new stronger diff is worth it. It's a package deal. Build a high HP engine and the rest of the driveline also needs to be upgraded to handle the extra power.

 

yeah, I guess you're right... But since mine is almost broken (making horrible clunking and whining noises)...

I think these 7.5's do fairly well with the 4th gen zexel torsen diffs and aftermarket 28 spline axles. I think I have broken more stock axle shafts (26 and 28 spline) than anything else in the assembly.

 

I broke 4 ten bolts and 1 9 bolt, finally made the jump to the 9" and won't go back to anything else. If money is tight run a moser housing and axle package and a junkyard center section. 4.11s and posi are in a ton of ford bronco's out there

 

"That won't work. You can't position it close enough to the center of the diff to line up with the back of the transmission. If it's off center, it will cause suspension alignment problems." quote by steph. i dont know how to insert a quote. anyway, see that makes sense to me too. i guess the purpose on the torque arm is to locate the arc on which the suspension travels looking at the veh from the side, but also it determines the fulcrum or center point of arc from looking behind veh. so i suspect with that setup, ibet it would handle better around say left corners then right, or... ive seen spohn torque arms, and they look nice like a dragster wheelie bar, i think i could fab something up that looks like that with bracing that runs from the trans mount down the driveshaft and then angle toward the axle tube next to the center section by the pinion shaft area. im not much of a corner carver anyway. but it just seems to me that everyone is serching for a way to mount a bracket to mount the torque arm. i say just bypass the mount provision. i like the feedback, keep it coming.
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also note: im poor, but i have a nice set of tools, a nice welder that runs 220, access to a plasma cutter, and all kinds of time.

 

ive reconsidered my reconsidered idea as nonsense. i have another idea in the mix, involving 2 ladder bars that run from both sides of the center section to a common point under the trans tailshaft. when this goes into production, you know ill post pics.

 

Ladder bars are a bad idea for a street car. Worse than bad in fact.

Think about what happens when you go around a corner.... one side of the suspension goes to "jounce", and one side goes to "rebound". Now think about what a ladder bar does: each ladder bar, which of course travels in its own arc, will attempt to twist the rear end to an angle, which is determined by the point in the bar's arc that it ends up. But in a corner, since the bars will be at DIFFERENT points in their arc based on suspension travel, they will each try to twist the axle to a DIFFERENT angle. How can that happen? The left side of the rear end, a solid and inflexible piece of metal, tries to twist to one angle, and the right side tries to twist to some other angle. {loud obnoxious buzzer sound }

That's how ladder bars WORK on the strip: they FORCE the car to go straight, because whenever the car tries to turn, the bars bind up and force it back straight. But that's also why they DON'T work on the street.

Run ladder bars of ANY design on the street, you WILL break stuff, sooner than later. No way around it.

There's a reason why the type of things that you see available, are available; and why those other things that "seem" to suggest themselves, aren't available. It's because the one group of things WORK, and those other common things, DON'T. Not trying to squash your atttempt at ingenuity; only to point out that you're FAR from the first person that's got this idea (it regularly gets posted on here in some variation by somebody new to these cars every few months), and unless you can re-write the laws of physics, it won't work any better for you than it has for anybody else.

 

well said. and i agree. i dont know whether ladders break with extended street service, but hey doesnt everything else. check out this ladder type suspension set up. this is kind of what im thinking, but running it up the tunnel. but then what the hell you do with the exhaust i have no idea. <a href="http://s116.photobucket.com/albums/o6/jeepboy73/?action=view&current=rearsuspension.jpg" target="_blank"><img src="http://i116.photobucket.com/albums/o6/jeepboy73/rearsuspension.jpg" border="0" alt="Photobucket"></a>

 

I love the idea of a GM 8.5" 10 bolt, and i've posted before why. If you're searching through the small handful of threads about this topic you'll find my thoughts on it.

Just weld a mount to the pumpkin. You just need to preheat it, and use 99% nickel rods. You don't just point and shoot it with mild steel rod, that will crack. With the right prep you should be fine. Or design something more ingenious as mentioned above - but stick with a torque arm.

If you have a drill press and an angle grinder you can just buy raw stock and make the mounts you need. LCA, shocks, springs, panhard, just make them and weld them onto the tubes.
Just make sure you measure such that the pinion is centered, and everything else is x inches outwards from that. This way the rear end will stay centered.

 

Those aren't ladder bars. They're triangulated trailing arms similar to the suspension system under mid 60's to early 70's GM pickup trucks. Although a system like that would probably work, I really don't know how much ground clearance you would have. The floor pan of a third gen is very low and the wheelbase is very short. Third gens also have no framework to hold it all together.

I'd guess by the time you finished fabricating something functional, you could have bought a bolt in 9" or 12 bolt for less money.

 

There’s a significant difference between ladder bars, torque arms, truck arms…

To start with, truck arms are each made of 2 pieces, angled in and bushed in a way that they can twist to allow both sides to basically act independently (or as much as a solid axle will allow). Typically ladder bars are rigid and mounted rigidly to the axle and don’t allow any independent motion from side to side, torque arm is somewhat like a single ladder bar with control arms designed to take up the motion that the second ladder bar would usually entirely prevent (our setups get more complicated by allowing motion that doesn’t exist in this description with the front sliding link).

There are all sorts of hybrid ways that you can do this that would give you acceptable to very rough handling with good straight line traction, but the easiest, most street able answer is to use the plasma to cut the stock brackets off and transfer a set of 3rd gen brackets to it, and then make a hoop that bolts between the center section casting and it’s cover with a mount point above and below like the GNX had cast into it’s rear cover.