Torque arm rear on Chevelle?

[LSxChevelle]

So how would a torque arm setup like that of 4th gen f body work on a 70 Chevelle as possibly cheap upgraded suspension?

Jason

[PTAddict]

Do a search in this forum and the advanced tech forum on "torque arm". Torque arms can certainly be made to work very well, but I'm not sure that it's especially cheaper or easier to do right than a 3-link. The stock 3rd/4th gen Camaro torque arm and axle were generally considered too weak for serious performance use - hence all of the aftermarket upgraded pieces. And it takes up space, either in the tunnel, or below the axle, that you may not have.

[rocketman]

i did a 69 camaro with a 4th gen style tq arm,used a bmr tq arm and a moser 12 bolt with the tq arm mounts,works great.

[LSxChevelle]

How does the stock 1st gen susp differ from a Chevelle and what did you have to modify?

Jason

[rocketman]

well a chevelle is full frame,a camaro is unibody.the way we did it was sub connectors,fabbed upper shock brackets,and weld the tq arm mount to the sub frame connectors.and make a panhard bar mount.had to slightly modify the tunnel.we left the rear alone except for mini tubs.

i will look and see if i have any pic's of it.i did it a couple years ago

[LSxChevelle]

I appreciate this info. I think I will look under my 98 Camaro I sold and compare to my Chevelle to check dimensions and where I can mount stuff. I can probably just order a 9in housing w/ 4th gen mounts for shocks and T/A and Chevelle mounts for the LCA's and springs with my desired width to accomidate the offset of the C6 Z06 wheels and have the proper C6 brake mounts? Now I'm wondering about the downfall of 4th gen rear susp.

Jason

[rocketman]

i did have to make a lower trailing arm mounts,seems like i had them send the rear end without t/a brackets welded to it,and i welded them myself after i made them.the car had 18x12's on 345/35's.

[Norm Peterson]

I appreciate this info. I think I will look under my 98 Camaro I sold and compare to my Chevelle to check dimensions and where I can mount stuff. I can probably just order a 9in housing w/ 4th gen mounts for shocks and T/A and Chevelle mounts for the LCA's and springs with my desired width to accomidate the offset of the C6 Z06 wheels and have the proper C6 brake mounts? Now I'm wondering about the downfall of 4th gen rear susp.

JasonI wouldn't say there's any basic torque arm rear suspension compromise that's bad enough to be considered as a downfall or a deal-breaker. A torque arm is a bit heavier than upper link(s), and the 4th gen F version is perhaps a bit more sensitive in terms of rollsteer vs ride height (this being the chief reason for LCA relocating brackets on lowered 3rd/4th gen F-bodies set up for hard cornering). And the anti-squat percentage falls slightly/somewhat as the rear ride height drops.

But once set up they're quite easy to drive hard, as they're pretty well-behaved. That an old guy like myself could climb into an ESP Firebird and, with no F-body auto-x seat time and having never previously driven on R-compounds in anything, run times within a second of the car owner's times has to say something about the basic honesty of the arrangement.

In a Chevelle application, if you can maintain at least some of the plan view angularity of the LCAs, this rollsteer sensitivity is decreased (my guess being that rear seat packaging constraints would not permit this to be done on the F bodies).

Norm

[PTAddict]

Now I'm wondering about the downfall of 4th gen rear susp.

Jason

I think if you surf the various boards on 4th gens, the primary downfalls of the stock setup are that both the stock torque arm, and especially the stock rear end, are not very stout when you start hitting them with big torque and sticky tires. Those problems are easily solved with aftermarket rear ends and torque arms.

Some companies (Global West, for instance) will tell you that the stock setup could use more anti-squat, and make shorter torque arm setups in order to achieve it. You'll get different opinions on just how much AS is really desirable; if you're not too worried about optimizing your 60 foot strip times, I don't know that I'd pay too much attention to that. I think your wheelbase is slightly longer than a 4th gen, which will give you a bit more AS anyway.

And as Norm said, the 4th gen geometry is quite good for corner carving - you never see 4th gen guys completely redesigning the rear suspension setup the way, for instance, '79 - '04 Mustang guys have to.

Edit: what Norm said above is significant - if you can keep your lower trailing arms angled in toward the center of the car, then you can adjust your anti-squat by angling the arms upward toward the front (more AS) or down toward the front (less AS) without affecting your roll steer too much. The stock 4th gen setup, with parallel trailing arms, will have undesirable roll oversteer if you angle the trailing arms upward.
That's a long winded way of saying, you'll actually have a more adjustable setup than the 4th gen, which ain't at all bad to begin with.

[LSxChevelle]

What do you mean that the T/A and rears are weak on 4th gens?? Oh wait...I snapped one T/A and grenaded a diff when I had a 1.89 60' on a stock car!

So to sum it all up you're saying that it would be good to get say a 9" housing with a f-body T/A mount and chevelle trailing arm/spring mounts?

As far as adjusting the trailing arms can I buy adjustable ones?

Thanks!

Jason

[Norm Peterson]

Adjustment for coping with the anti-squat/rollsteer compromise involves having some method of vertical adjustment in the LCA brackets, not in the LCAs themselves. Axle-side relocation brackets with multiple holes (or slots and a method of positive pivot location) is one possibility. Something similar on the chassis side is another. Or even both. What you're doing is altering the LCA inclination (its force line, actually) as seen in side view.

Adjustable LCAs can certainly be used, but in a TA suspension their only significant function would be for final squaring of the axle in the chassis.

Norm

[LSxChevelle]

Would an adjustable T/A help this as well? And are these what you are referring to?

http://www.lmperformance.com/1478/1.html

Jason

[rocketman]

no,you need adj tq arm,they adj to set pinion angle.check out bmr they are a site sponsor.

[LSxChevelle]

Now a 4th gen f body uses a panhard bar...would I want to run one?

[zbugger]

Now a 4th gen f body uses a panhard bar...would I want to run one?
Yes. It's the only way, besides a Watts Link, to locate the rear end.

[Norm Peterson]

You'll also want to brace the PHB's chassis side bracket, as the PHB carries the entire rear lateral load (this could be 1500 lbs or more, without considering bumps or curb scrapes). Most arrangements run a bar to the opposite frame rail. For the same reason, the axle side bracket needs to be fairly substantial.

Norm

[LSxChevelle]

Sounds like a good route to go....