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Thank you so much for your answer and your picture, what kind of suspension is this?
It's a torque arm and Watt's Link from Griggs Racing. Watt's links provide very consistent geometry that make for nearly instant response, and torque arms control axle wrap and help to plant the rear tires by pushing them into the pavement. As the axle tries to wrap up from the torque, the torque arm pushes against the car, lifting it. The whole thing together makes for a very stable, predictable platform that handles very well.
 

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Discussion Starter · #23 ·
Having experienced a stock rear end, IRS of a couple different kinds, 4 link, and 3 link, I can tell you that there's quite a difference between most of them. All of them with a straight axle do great in straight lines and on smooth roads. However, when turning under power on uneven terrain, the IRS setups are much better. Live axles tend to jump around, skidding to kick the tail out, if you go over small bumps while turning and on the gas. It's something you get used to, but it's a very odd feeling at first. Independent rear suspensions feel a lot more planted, and a small surface irregularity under one wheel won't make the whole back end waggle.

The early Arning Mustang setup is probably best all around, because it's got excellent geometry, the brakes get plenty of cooling, and of course, it was engineered to fit an early Mustang. Unfortunately, it'll set you back at least $7k. Jag IRS works pretty well too, and has even better ride quality due to less unsprung weight, with the brakes next to the pumpkin. But unfortunately, that brake placement does cause them to get pretty hot, because they aren't getting much airflow in that position. It's not as good if you're doing downhill, or any kind of spirited driving where you're off the gas and on the brakes a lot. Late model Mustang IRS swaps will fit... sort of. The whole setup is a lot wider than the early 'Stang back ends, so it ends up just not working well, and the back wheels poke out awkwardly even if you shoehorn it into place.

As for the straight-axle setups, I'm not a big fan of the 4 link setup, because it tends to wear out and make a lot of noise, along with binding when cornering hard. Drag racers seem to like 'em. But then again, you're talking about guys who also love to take most of the front suspension out and run bicycle tires, when they can get away with it. 4 links do plant the tires hard, but they are mediocre in the handling department. The three link is probably my favorite live-axle setup. It's lighter, simpler, and just seems to work very well. Usually it ties into a nice subframe brace, which helps with body flex too. Doesn't try to hop under hard acceleration, either! The one I got to try out really did well, and while sometimes in a corner you could tell it wasn't IRS, it still impressed me.

If you want cheap though, just fix up your stock rear end, make sure the springs are in good shape, replace the bushings, and get some Bilsteins! You'll be surprised at how well it works.
Thanks for your words, but 7k is too much... Then 4 links is more for Drag races? Could you recommend me a aftermark brand for 3 links?
 
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Thanks for your words, but 7k is too much... Then 4 links is more for Drag races? Could you recommend me a aftermark brand for 3 links?

RRS Racing also has a good one, and their videos are fantastic, but StreetOrTrack is here in the US. They'd cost a little less and offer the same quality. You couldn't go wrong with either.

If you look at the 04 Cobra installation, you will also notice that despite having wheels with a crazy offset to the inside (I.E. - the hubs are flat on the outside, not dished!) they still stick out just a little, and required some fender work. I don't care for the look, even if it works okay.
 

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Discussion Starter · #25 ·

RRS Racing also has a good one, and their videos are fantastic, but StreetOrTrack is here in the US. They'd cost a little less and offer the same quality. You couldn't go wrong with either.

If you look at the 04 Cobra installation, you will also notice that despite having wheels with a crazy offset to the inside (I.E. - the hubs are flat on the outside, not dished!) they still stick out just a little, and required some fender work. I don't care for the look, even if it works okay.
I am going to check this RRS Racing and the Street or Track, thanks!
The owner means that it is a lot of work, but anyway in Spain I need to check my car in a technical inspection center and is not allow to cut the body...
 
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Discussion Starter · #26 ·

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I think it'll work fine for a while, then badly, because 4-link. Just the nature of a cheap 4-link setup.

Pros: It'll help control wheelhop.

Cons: It won't really be appreciably better than a leaf spring setup with good shocks, just more expensive. It will wear out and end up noisy, hurting your handling significantly. It's more expensive than other fixes for wheelhop.
 
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