spitfire350

does anybody know what a 4-link is. i have heard it is more street worthy than ladder bars. and do any companies offer one for 3 genners? thanx for the help!

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keep the stang's far behind u and the cops even farther

RB83L69

Look up under a Chevelle or a Caprice sometime. Those are 4-link designs. Notice that the uppers do not go straight from front to rear, but rather from the outside at the frame to the inside at the axle; that provides lateral stability. Ones for racing are more complex and stable, usually with various adjustments, and usually include a Panhard bar. Our cars are "3-link", so to speak: 2 LCAs and the torque arm, plus the Panard bar to locate the rear axle correctly from side to side.

Ladder bars are a 2-link arrangement, where each "bar" attaches to the axle at a point above the rear end and a point below it, to hold it at the correct rotation (pinion angle). They also require a Panhard bar.

As you can clearly see, ladder bars can only be adjusted correctly for exactly one thing: drag racing. They hold the pinion always pointed exactly at the transmission output, which is great for power application but may or may not work well for driving over bumps. A 4-link allows the rear end to articulate up and down in more of a straight line rather than in an arc around the front mount of the ladder bars. Also, since the entire force from the rear end is exerted on one spot with ladder bars, they require a somewhat different chassis setup.

There's nowhere to mount the upper links to in a 3rd gen F. So there's no way to put a 4-link on a stock chassis. A tube-frame thing or some such would be required.

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"So many Mustangs, so little time..."

crazeinc

So what physically happens when you have ladder bars installed when you go over a speed bump let's say.

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82 Z28
355 carb'd, Edelbrock Performer RPM package (minus heads), Hooker Super Comps, Mufflex 4" offroad y-pipe, 700r4 with B&M shiftkit, '85 IROC 10 bolt rear with Richmond 4.10's & Auburn posi unit, Lakewood 50/50 drag shocks. Shooting for 3000lbs w/ driver.

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[This message has been edited by crazeinc (edited October 23, 2000).]

AlkyIROC

They bind. Because of the design when one wheel rises or falls, the other one wants to also. Since it can't, the suspension will bind. Bigger bumps used as examples. If the RH wheel goes over a big bump, the LH wheel should actually lift off the ground. If the RH wheel goes over a pothole, the LH wheel would actually keep it from dropping all the way in.

Although it sounds like an ideal suspension it isn't. The suspension is constantly under expansion and compression from road irregularities. This would be transmitted as a rough ride.

4-link suspensions such as the factory setups in A and G body cars allow the rear wheels to travel freely over bumps without binding.

Although 4-links and ladder bars are what third gens require to get a better suspension, the factory design of the car limits how they can be installed. Look at an older f-body. You'll see the floor is sitting higher than a third gen. This clearance undernieth is whats required to properly install ladder bars. The differential is more inline to the bottom of the floor. On a third gen, the diff is much higher than the floor. To use traditional ladder bars, the floor would have to be cut since the front of the bars would have to mount under the rear seat.

It's possible to install a 4-link system without cutting the floor but more fabrication is required. The easiest way is to backhalf the car. This is putting a new rear frame section in that provides mounting points for the front of the 4-link system and the upper mount area for the coilover springs.

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Stephen's racing page

87 IROC-Z Pro ET Bracket Race Car and knocking on the SuperPro ET class
383 stroker (carbed) with double hump cast iron heads and pump gas
LS6 Big Block buildup now in progress

Best results before the engine blew up
Best ET on a time slip: 11.857
Best corrected ET: 11.163
Best MPH on a time slip: 117.87
Best corrected MPH: 126.10
Best 60 foot: 1.662

Racing at 3500 feet elevation but most race days it's over 5000 feet density altitude!

Member of the Calgary Drag Racing Association