Puting a 4 link on a unibody???

[aseaman92]

ok this might be crazy but, i'm in the process of putting a ford 302 in a 1992 nissan 240sx. It's a unibody car with independent rear suspension but that is not good enough so I'm wondering the process in changing that into a 4link. i would be using a ford driveline(engine, transmission, drive shaft, and rearend). so if you know of anyone that put some type of solid axle in the rear of a unibody let me know i'm sure a couple of mustang guys did it.

 

[GregLocock]

I've done the reverse a couple of times. You are right the Mustang enthusiasts tended to throw the Cobra IRS away and fit a live axle instead, hence the ready availability of nice IRS modules.

Realistically your main problem is deciding on arm lengths you can package and position that give reasonable control over the pinion joint angle. This is a classic 4 bar link problem, there are many solutions. The V8 supercars over here use long, parallel arms, and then a Watts link. Our sedan used the same (the one is based on the other), but we had a shorter upper arm, angled inwards and down, for roll steer and to help toggle the pinion angle.

You may need to biff the floor to create clearance for the diff.





Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[NormPeterson]

The Mustang guys had it a bit easier than what you have ahead of you, as that car's IRS was designed to fit up to the same points as the stick axle that was concurrently offered.

I doubt that your car has adequate strength where you'll want the upper link(s)* to attach, and adding only local panel stiffening around any additional brackets may not be enough either. It wouldn't hurt to 'overbuild' a bit here for stiffness as well as for strength, as you may find you have wheel hop under either hard acceleration or hard braking where there would be some sort of impact factor involved. At least the few extra lbs would be more or less over the "right" wheels.

* Depending on what you're going to do with the car, you may want to consider a torque arm suspension (a la GM's 3rd/4th gen F-body and a fairly common retrofit to the Fox Mustangs) or a 3-link (as in the latest S197 Mustangs and also a retrofit for the Fox/SN95 axle, and I suspect is also used in Greg's supercars and sedan) instead of the triangulated 4-link.


Norm

 

[NormPeterson]

Late thought.

The Mustang guys swapped out the IRS for reasons of dragstrip durability, but I'm guessing that's not the environment where this particular conversion is headed.


Norm

 

[Cargeke]

You can get 'back-half' kits from Jegs or Summit that come with the trailing arms plus some weld-in frame rails. They're generic, but that could be a good thing. What do the drift guys do to the 240SX suspension/drivetrain to make it hold up? I know that's a popular car for drifting. I've seen Skyline engines in them. If the car will handle a Skyline engine, it'll handle a warmed-over 302. There's also a company that engineered an IRS using Ford 9-inch components for muscle cars. It's actually a Ford design that the beancounters thought was too expensive to put in the Mustang in the 60's. It's really sweet, but a little pricey

'When in doubt, make it stout, out of stuff you know about.' (It'll help plant the rear tires and give a better weight balance too.)

 

[Bribyk]

I read that Ford could've put any IRS on the current Mustang for $400 per car, but their market research showed the drag folk wouldn't have it.

Unless you're drag racing this 240, why would you get rid of the IRS? What's not "good enough"?

 

[hemipanter]

What is the use of the car?
Goran

 

[GregLocock]

Norm - no, it is a genuine 4 link, in the Supercars they use long parallel equal length arms. Our suspension was the basis of the Mustang one. There are a few circumstances in which the IRS is better than a beam axle, but a good beam axle is better than a bad IRS most of the time, and cheap IRS tend to be bad.



Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[aseaman92]

how about a Solid-axle, with a coil-spring

because i was told that the car would handle poor on the road and this would be a bit better.

ok the car is going to be a street/strip but down the road i might just make it into a full out drag car not sure.

I think im going to be tubing it, to free up a bit more space, and there will be a cell going in the hatch of the car so that there is even more space for the diff and suspension components.

the drifters just use a infinity rear end i am pretty sure its a 2.0 or 1.5 lsd not that sure on any of that but i need or i guess i want a possi just so i can launch the car as hard as possible and go straight down the track.

But what i want is a solid drag car with a rear end that will almost never fail so what do you guys recommend for my setup/

 

[patprimmer]

I would recommend a Ford 9" centre with drive shaft flanges on axle stubs. Install it where the stock diff is and adapt the heavy duty drive shafts from a V8 with IRS.

f you are serious about your drag racing put in a Detroit locker or an air shift type locker. A Positraction won't cut it.

If you run substantially bigger tyres and/or slicks you will need substantial reinforcement of stock dimensioned suspension arms and their mountings and the chassis platform in those regions.

Normal method for moderate increase is to box in the channel sections and to add thicker plates at the mounting points, but if the power and more importantly the traction increase is substantial, you will need fabricated arms with more robust construction, but same lengths and the mounting points should be on the links that link the font and rear chassis sub frames, or to cross members mounted to the sub frames or chassis links.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers for professional engineers

 

[patprimmer]

Where are you, might be ableto hook you up with some chassis fabrication guys

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers for professional engineers

 

[hemipanter]

A road race car is often using very long 4 link rods, maybe all along the sides of the car, even if inside the bodywork and not visible. This is to free up from "roll lock" that will occure using drag racing style unequallength 4 liknk.

So in your case a shorter rod 4 link is to prefere. It should be adjustable for different instant centre to be able to run unparallell when racing, then go back to parallell when driving home. The trick at the strip is to set "rise" or "antisquat" to produce tire plant during start. Then you should have special Dr shocks where you use the extension dampening to alter the time duration vs force of tire grip. If you got the money, buy doubble adjustable shocks in order to be able to alter the after 60 foot distance grip.
Springs are usually quite soft, and you might even use a heavy swaybar to set off the line side to side preeload.

Get the picture?
Goran

 

[Cargeke]

How fast are you planning on running? The Ford 9" and the Dana 60 are bulletproof axles, but they're kind of heavy. With a light car and a C-clip eliminator kit, a Ford 8.8" would probably do the trick. A Mopar 8.75" would work too. If it sees limited street time, a spool instead of a diff would probably be better. Sticky tires will shred a weak rear end pretty quick.

 

[patprimmer]

would never use a spool on the street.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers for professional engineers

 

[aseaman92]

i live in prince edward island, Canada i know that there is no chassis fabrication guys on the island but if you know any in the maritimes that could be helpful.

im not to worried about weight i will just make that up with a couple more HP and will also make up for it with fiberglass and possible some carbon fiber. I have a 9" already so i might try to save some money and just use it.
i really want to get rid of the IRS so a 9" with axle hubs is not for me but thanks for the good advice.

yeah patprimmer is right a spool is not a option for the road.

but what do you guys think of that 2link i guess thats what it is called with the coilovers it look like the easiest one. the 4link just has to much involved for how much time and money i got.

it would be nice to run mid 10s to 10s if possible but that is a lot farther down the road i'm thinking right now 11s or high 10s.

 

[JohnLear]

Spool on a road car is a PITA, I had one temporarily in a Lotus 6/7 type sports car (i.e. a 'Nota Sportsman'). Not reccommended at all mostly because it will actively try to kill you on a wet road (even at walking pace...).

The one redeeming feature is that if you snap a half shaft you can still get home, but one wheel drive does have some 'interesting' characteristics...

 

[patprimmer]

The 2 link is very similar to what I call ladder bars.

ladder bars bind in roll. They also need a Panhard rod or Watt link to control sideways movement.

The bind in roll or a single wheel bump makes them very inconvenient on the street. For dual purpose you need a 3 or 4 link setup with a Panhard rod or Watts link.

I will enquire about fabricators in your part of Canada.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers for professional engineers

 

[aseaman92]

hey thanks so i think i would try to go with the 3link because it is a little less complex then the 4link and might take up less space.

 

[Cargeke]

NASCAR uses the 2-link with coilovers suspension. It's a design from old pickups, Chevy I think. The arms went from the axle to way up near the cab. My first thought is that if you went with a long 2-link, it would help with weight transfer to the rear axle due to leverage. Not sure without some study, but that's what my intuition says.

 

[hemipanter]

I just shot an image of a Shelby Mustang rear end we are building. No Panhard bar but a diagonal track locator.

http://www.hemipanter.se

very fare down the site. Sorry that my camera battery went drained so there is only ONE image.
Goran