Differences in rearends

[Snakebit54]

Hi All,

What are the differences in the types of rearends you can order from some of the manufactures.

What is 3 link, vs. 4 link, vs. IRS? I can and do understand the difference between the size i.e 8" vs. 9". I'm asuming the larger the rearend the more stress it can handle, correct?

Let me finish by saying that I do not intend to ever race my car. Neither oval or drag. So, for someone who just wants a nice show quality, 450HP car that will be driven only on sunny days around town what would be the most economical rear end/suppension to go with?

Thanks in advance for all your help and suggestions.

Eric

[Adrian472]

Eric
Firstly i would have to say it all depends on what kits you are looking at buying and what suspension layouts they offer.
3 and 4 link rears are typically for a solid axle and IRS is a independant setup with top and bottom links and a halfshaft per side.
If your plans are just a sunny day cruise then either a 3 or 4 link rear would be fine and wouldnt justifiy the added cost of a IRS set up.
I hope this infomation is some use to you.

Adrian

[Snakebit54]

Thanks Adrian for your input. So, does that mean that an IRS is only for racing and has nothing to do with drivability or how comfortable the car rides?

Also, is 4 link better than 3 link if money were not a factor? Or is it just a manufacture difference?

I'm thinking of going with either FFR or Shell Valley.

[Adrian472]

Eric
IRS gives you a better ride all round handling etc. It really depends how much money you want to chuck at it you can go either way.
3 link panhard rod set up or 4 link rear end? Both set ups give the axle more solid location fixing and tries to prevent axle movement from twisting on its self during cornering and acceleration.
I would go for the Factory five kit and then u have the choice of a IRS or solid rear and both can be changed at a later time.
A good rule of thought is go with the best your money can buy.
Adrian

[Goober]

Eric, if you are just going to use the car for street, the solid rearend will work fine for you. If you kit offers the IRS for a low cost, get it. They tend to ride a little better. However, if you ever drag race, you will want a 9" or something similar. IRS setups are a little more complicated than the old solid rearend, but most kit companies that offer them are pretty much plug and play. Superformance uses the Ford 8.8 IRS while Backdraft use a BMW IRS. A lot of companies use the Jag IRS which usually has the discs inboard as opposed to the outboard discs that are normally found on most factory cars. Basically the links you speak about pertain to how the rearend is hooked up to the car. Pertains to traction and sway issues and the way it hooks up.
Come to our meeting next Saturday and you will get a chance to see all of them and talk to the owners.

Mark

[feddersenr]

FFR offers three different rear suspension options.

1. The standard FFR kit without a rear suspension upgrade uses the stock 4-link out of a mustang with a solid axle rear-end. The stock 4-link causes a lot of grief when setting the ride height. Also, the 4-link will tend to bind a little in the corners when pushed really hard. You'll get a stiff, harsh ride with a 4-link.

The big advantage to the 4-link is that it is very strong for handling the launches with big motors. If you are on a tight budget, it's one place to cut corners and you can upgrade later. If you want to upgrade the 4 link without going all the way to a 3 link, you can ditch the stock springs and shocks for a good set of coil-overs for around $400.

2. For around $1k, FFR offers a 3-link upgrade that includes everything you need to attach your rear-end to the frame, including the coil-overs.

The three-link is a huge improvement in ride comfort and car handling. You'll get much better cornering response out of the car, yet it will still handle a lot of horsepower. The best bang for the buck upgrade in an FFR is definately the 3-link.

3. For around $2k, you can upgrade the stock FFR kit to include an independent rear suspension. You will need to provide a Ford Thunderbird Super Coupe rear-end (pumpkin, axles, rotors, etc), but you will end up with an excellent ride quality and fantastic cornering abilities. Is it better in the corners than the 3 link? That depends on the driver, really.

The IRS will increase the resale value of your car as well, but it is a more complicated piece of machinery. You will need a rear-end alignment when you get everything put together. From what I understand, and I may be wrong, but the IRS is not as strong as the 4 or 3 link, so you may want to carefully check into how much HP and torque it can really handle.

Finally, there's great FFR information at the FFcobra forums. Check them out at http://www.ffcobra.com

Enjoy.

[Rich A]

There is a 5 link for the Factory Five.
They call it a 5 link but it's a 3 link with a Watts link system.
Levy Racing offer the 5 link system.
They say this is the best.

[DavidNJ]

I believe the FFR forces their geometry to fit the stock 4-link. This is, that is the original Ford design, a low cost design for low powered production cars. The three links replace the angled upper links with a single straight upper link and add a panhard bar or watts link for lateral location. The lower links remain angled. The Levy kit attempts to straighten the lower links as much as possible without moving the FFR mountng point on the frame.

The FFR IRS uses the Ford upright (as does the Superformance, Hurricane, Turn Ten/D&D, JBL, and I sure others) which mandates a specific mounting arrangement. Longitudinal and rotational forces are primarily (solely) resisted by the lower control arm. Some other manufacturers (including Kirkham, CuttingEdge, and Prestige) CNC or fabricate an upright, allowing more geometry flexibility.

Net, if you got the 3-link free in FFR's winter sale, that's ok. Otherwise the Levy 3-link or the FFR IRS is your best choice.

[Smitty1]

I believe the FFR forces their geometry to fit the stock 4-link. This is, that is the original Ford design, a low cost design for low powered production cars.

I think what they are trying to say is that the Standard FFR rear is a Triangulated Four link. This uses 2 upper and 2 lower control arms. These arms are angled in pairs...Upper and lower. Each pair is angled either toward the center of the car or angled toward the outside of the car. This allows the control arms to not only allow up and down movement of the Rearend, it also holds the Rearend centered . The most popular drag race specific set up is the parallel 4 link (as opposed to the Triangulated 4 link). This set up places all 4 control arms parallel to the chassis and requires a Panhard rod to be mounted diagonally from the frame to the opposite side of the Rearend to keep the rear from moving left and right. Ford uses the Ring Gear Diameter to describe their Rearends...a 7.5 rearend has is a 7 1/2" ring gear, 8.8 has a 8.8 ring gear etc. For the power level and the uses you describe the "Standard" FFR Triangulated 4 link will work fine.

[Lowell W]

Lots of good info above.

One slight correction: SPF did use the Ford 8.8-based IRS but the newer cars have an Australian (I believe) Dana IRS. Not sure how this compares to the Ford strength-wise, but apparently Ford has stopped producing the 8.8 IRS so SPF had to source their parts from another manufacturer.

There's a good article on Ford 8.8 rears in the current (Marked "June" but who are they kiddin'?) issue of Car Craft. It compares the relative strengths of the 8.8 and 9" Ford and 12 bolt GM axles and has suggestions for mods. The gist of it all is that you can upgrade the 8.8 to 31 spline axles and diff, giving you 30% more torque capability. BUT...you can build the car now with the 28 spline axles and upgrade later if you break something or make more power.

A few observations: The original cars used IRS. I've read or seen in print that, since these cars have such short driveshafts, suspension travel with a solid rear is necessarily rather limited. Also, point well taken that the IRS will add more to the value of the finished car when it comes time to sell it. The IRS may also be a little lighter, with an aluminum center section, although the axles are heavier...may be a wash.

If I were building the car, I'd go for the IRS upgrade initially and sacrifice somewhere else, if necessary.

Good luck with your build.

Lowell

[fastraxsg]

When you are considering 400 + hp. consider opting for bigger stronger brakes too. Might be better to spend money there than some other places for glam or bling. Most kit cars out today can offer IRS so do your shopping wisely, see what you can get for your dollar, most every kit out there today is well thought out and can be made to run and drive great. Some need donors, some have it all, some need a lot of parts chasing.