torque arm 3 link VS 4 link

I have a 1970 Torino GT, with a pump gasoline 572 stroker, C6 and a factory rear suspension (9 inch 4.10 Detroit locker)

obviously i dont hook up AT ALL... so the car is going to the fab/chassis shop.

For a street driven car, whats the better way to go? whats the pros and cons of a 4 link w coil overs vs torque arm 3 link?

Shane

ps I am an end user, NOT a suspension expert. so please excuse any ignorance on my part, any ommitted info etc..

I'm guessing by "torque arm" you're talking about a single, long, almost centerline mounted (along side the driveshaft) "ladder bar like" arm......


Both a long single torque arm and a "street type" 4-link would both be decent choices for a truly street/highway driven car. Both will most likely need some sort of a springy/flexible rear sway bar (not a rigid anti-roll bar) to allow, (but control/dampen) some amount of body roll to happen. Choosing between the two might be a hard decision since there are a few different ways to do a so called single/centered "torque arm".

(A) Cheapest setup, a so called "1-link" swing arm with leafsprings. A 1/2 & 1/2 mix of factory & aftermarket type parts. Stock leafspring setup for housing for/aft placement, spring action + 1 aftermarket center mounted long torque arm for pinion rotation control & suspension leveraging application). This setup could have either a multiple bushing pivot/shackle front joint, or a single bushing front joint on the front of the torque arm. Using just a single front torque arm pivot bushing joint with this setup will increase the chance of possible suspension binding, but some people like the single front bushing because is simpler. In truth this could probably be called a 3-link since there are actually 3 forward active suspension attachment points to the frame/chassis. But since the leafsprings aren't "rigid" links, some people just call it a 1-link.

(B) A so called "3-link/torque arm" setup with coil overs. A 100% aftermarket setup using 2 short lower control arms for part of the housing for/aft placement + 1 center mounted long torque arm for pinion rotation control & suspension leverage application, plus part of the hosing for/aft placement + coil overs. This setup usually has to have a single front bushing on the torque arm (and not a multiple bushing shackle/floater) since it also partly controls for/aft housing placement. Because of this there is a possibility of some suspension binding to happen between the long torque arm and the shorter control arms if the car needs a decent amount of rear suspension travel. This setup should really be called a "2+1-link" since there are 2 forward active attachment points (the 2 lower links/control arms) plus one forward active attachment point (the torque arm).

(C) A "true-full" 3-link plus torque arm setup. A 100% aftermarket setup using 2 short lower & 1 short upper control arm(s) for housing for/aft placement + 1 center mounted long torque arm for pinion rotation control & suspension leverage application + coil overs. This setup can use the multiple bushing shackle/floater on the front of the torque arm most of the time since the torque arm doesn't control any part of housing for/aft placement. The truth about this type system is it's kinda redundant in a way when talking about "better traction". This is because the 3-link it's self will also be trying to control pinion rotation & suspension leverage application at the same time the torque arm is. This setup should really be called a "3+1-link" since there are 3 forward active attachment points (the 3-link) plus one forward active attachment point (the torque arm).

(D) A "true-full" 4-link plus torque arm setup. In my opinion these are even more redundant in reference to "better traction". What real benefit is the torque arm since there is already a 4-link there? Short of being able to use super soft bushings for a smoother ride at every suspension point because there are so many attachment points to work with I cant really see the need of this type setup.

It should also be noted that if someone was looking to stay with leafsprings vs using coil overs, there is a lot to be said for the simplicity of a well made set of decent length slapper bars vs the little more complicated single torque arm setup. On the other hand the single torque arm setup can usually bring a longer I/C length (vs a cheap slapper bar) to the table.

Wow, alot more options than I was aware of. My car certainly is NOT an open wallet project, but I also wouldnt consider my car a budget build either.

Assuming I have a budget of say 10k? 15k? or there abouts... and knowing this is a street car, I want to retain the full interior. Straight line performance is my only real concern (dont see many 70 Torinos cutting up road race courses) a 15 inch wide tire is about as big as id like to go. I want to hook 750 horse on the street and money is NOT the deciding factor. (I want the car to squat and go when I hit it) which way would you go?

Shane

15 inch tires and full interior generally dont go together. You will almost certainly have to modify the wheel tubs and probably have to relocate the rear frame rails as well.

A four link set up will also likely involve serious reworking of the rear floor/back seat area. Not to mention the fact that some kind of cage or bar structure would likely be required to reinforce the upper mounts at least.

I have never worked with a three link personally but from a packaging perspective that seems like your best option.

dkp

bosshoss wrote:15 inch tires and full interior generally dont go together..........................

Good point.

If the Torino will be getting a slick/tire with a 15" wide tread (and thus be 17-19" wide including sidewalls) and are going to have to back-half the car ,(and loose the rear seat) then an equal length street 4-link is probably the way to go.

On the other hand if the 15" wide slick/tire measurement includes the sidewalls, and you can find a way to squeeze them in using the stock/modified factory rear frame rails, (and keep some amount of the rear seat) then your choices are probably going to be........

Leafsprings moved inboard + good slapperbars

Single torque arm + either moved leafsprings or coil overs.

Aftermarket unequal length street 4-link using real short height housing brackets + coil overs.

Fox Mustang style 4-link layout (unequal length bars with top bars pointing outward).

Thanks for the info guys... I would certaily like to keep the back seat, as I want the car to retain some amount of street car/muscle car appearance.

When it comes to "15 inch tires" im not sure if he was refering to street radials, drag slicks, overall tire width, tread width etc... I know i really dont want a 33x18 inch type tire and a full out tubbed car... I kinda wanted somthing along the lines of a 325/60 (?) size tire, on widened factory steel wheels. maybe thats not enough tire to hook up on the street? any opinion on tire size? and maybe hes wanting to go with the torque arm/three link due to packaging and retaining the rear seat.
Regardless of type of suspension being used, im fairly certain im ditching the (factory) leaf springs in favor of coil/over type springs.

Shane

Here is a pic of a Griggs T/A setup. The only downside I see is they are usually light duty for road racing etc. I don't know if they are rated for a big 572 with slicks. I would call Griggs and ask them.