how to install independant rear suspension

[speedvisioncavalier]

ok, someone brought up the subject, so i figured i could share some of what I've learned. so far, all i have done is research this, and find parts from the boneyard for my project, but i haven't accomplished it....yet. alot of this info i got from dave.org, who own the j-body.org website, and has talked to alot of gm guys, who seem to love putting the grand am independant rear suspension on their Jbdoy show cars. turns out, there isnt much to it at all.

lets start with the assumption that you have a 3rd gen cavalier, and you have found a donor grand am, or alero or something late model N body to . these cars are already setup to accept a strut in the rear, which makes this swap VERY simple in theory.

here are the complications. dave.org says, the IRS rear suspension is about 2" wider from wheel to wheel than on the Jbody, or you can split the difference and say that just laying the suspension under the car, your rear wheels will be about 1" closer to the edge of your rear fenders than stock. the other issue is that the rear subframe, where your lower control arms connect to the chassis needs to be mounted 1/2" an inch lower than where your chassis currently is. also, a small issue is how to route the parking brake cable. some late model Nbodies had a foot operated cable, but i think the grand ams had a hand brake. choose a car with a hand brake to make things simple. last, your exhaust will need to be reconfigured to go around the new suspension.


now for the fixes. the suspension is too wide, and will make my wheels stick out some. well, most people notice their wheels arent all the way out to the fenders anyways, and can afford to make them an inch wider, and the wheel will still tuck. if you fall into this catagory, then your first problem is already solved. if you are sure you dont want to let the wheels be slightly wider, then get ready to fabricate some new lower control arms. when GM does their conversion for the show cars, they simply cut the old arms, and reweld them with 1" missing from each of them, thus solving the problem. however, most of us dont weld for a living, and i wouldnt want my whole rear suspension depending on my welding skills. besides, its cheap stamped steel anyways. you would need to make your own lower control arms using heim joints on the ends, and some sort of tube for the length of the control arm. this is real racecar fabrication, and precise measurements and clearances are critical to success.

problem 2, a 1/2" steel or aluminum spacer plate is needed to set the subframe correctly. find some metal, cut it into an appropriate shape, and drill holes into it to allow you to run the bolts through the spacer and subframe and into your chassis. you will know what im talking about when you get under the car. its pretty simple. the spacer just goes in between the subframe and the chassis.

problem 3 can be solved my choosing a good donor vehicle, with a hand brake.

problem 4 and so on. your exhaust will need to be changed to clear your new suspension. take it to an exhaust shop, and git 'er done. also, expect minor things to pop up, like you may need to change some minor things like brake lines, and making sure they can reach the chassis of the car where your old brake lines were. chances are high that it will match up anyways, but just keep this in mind. nothing too difficult if you use a little imagination.

and finally, issue#5. those grand am IRS suspensions use a 5x115 lug pattern, but your Jbody uses 5x100. you will need wheels that use this pattern, or buy a set of wheels that have a dual lug pattern, so they can match the front wheels. if you read the article on big brakes, you know the caddy front disks are 5.115 also, so putting on this rear suspension would make your front and rear lug pattern match. :)







now, if you have an even older Jbody(1st and 2nd gen), or an Lbody, then you have all those those issues and one more. the rear suspension you have right now uses a separate coil spring, and shock, not a strut like the grand am IRS. this means the struts that come on the IRS will NOT bolt up to the shock towers. you will need to find a way to either change to a coilover system, and run that instead of the struts, or convert your shock towers to accept a strut. since i have an older Jbody, this is the issue that is preventing me from finishing this conversion. i alrteady have money in my stock suspension, so im not going to go to IRS and disks, unless i have some good coilovers to go with them. these cost alot of money to be fabricated from scratch, so im working on other aspects of the car for now.


so, NOW YOU KNOW.

[bbechtel16]

Scary........

Anyone want to do an old friend who lacks advanced fabrication skills a favor? :D

[speedvisioncavalier]

ok guys, tell me honestly. do these tech writeups that i do seem to be too far involved for most people? like, yes it can be done, but you have to change so much, its just cost prohibitive? or the work involved is not something that most people know how to do anyways?

i have other things on my mind about what i could write about, but im really thinking about stuff you guys probably dont know how to do alredy anyways. i figure you dont need articles on how to make clear climate control knobs.

[darkfox]

no i think articles like these are EXACTLY what we need. To many other sites are bogged up with stupid stuff like how to ake climate control knobs or make a custom guage pod or how to make clear lenses. We have REAL technical articles!!! Its what differentiates us from the other forums. :D

[speedvisioncavalier]

well, if you guys want more really technical stuff, then i will get to work putting the stuff i know into writing, and telling you guys how to do it.

[bbechtel16]

Dude I love your writeups, its just I'm not that good. I don't have much experience with vehicles really. Not confident enough in myself to go try that. ^^^

[Quasi Mofo]

Yeah keep up the good work. I am using a few of these on the 94 Grandamnit.

I will look into the design and production of a narrowed subframe to keep the suspension geometry correct on the rear. Shortening the A-arms is a bad idea because it changes your camber and caster curves on the rear.

Why not use a Late model Grand Am/Alero/Malibu disc brake master cylinder instead of the Camaro MC?

[judgez24]

nice, my buddy is doing an irs setup in ihs 88ish ga and i wanna do it in a year or so myselkf in my 3rd gen j, and this sounds simple enough to do, only problem is finding a proper ride height spring to go in the back to match the front. other than that sounda really somple and having the back tires out an inch wil actually make the car look human,i hate the way the stock wheels are tucked in, my old rims were an inch wider and they sat more or less flush withthe uarter panels and looked awsome.

thanks for the right up man, lots of great info

[speedvisioncavalier]

Originally posted by Quasi Mofo


Why not use a Late model Grand Am/Alero/Malibu disc brake master cylinder instead of the Camaro MC?

well, i guess you could use either one, if you wanted, but i dont know the size of the late model Nbody master cylinder. i do know the camaro one is larger than stock. keep in mind, those caddy front brakes are alot larger than the Nbody ones, hence the need for more master cylinder capacity.

also note, these will be some extra issues if you are an ABS vehicle, because they have extra stuff happening there. curtis walker and I both have 91 cavaliers, the last year of non ABS models. the camaro master cylinder he used was from a 3rd gen camaro, which was also non ABS, making things alot simpler.

[Nemesis_y2k]

Dude, keep up your write ups. Your 2.3 into second gen has helped me, and this one also. I'm waiting to finish my engine and will eventually proceed into doing this. My car...

http://thetreestump.mine.nu/treestumpsunfiregtz.html

Right now my oil pan is in the machine shop to get nipples welded for the lower torque strut brace mount. :D

[89lxstanger]

well i am the one doing the 88 GA IRS, as judge z24 mentioned earlier

now mayeb this wont maek sence but i think it would work with a little planning
my wheel wells are rotten on my ga like most of that era i am sure however the rest of the car is spotless, i was contimplating cutting out my wheel wells and welding in the wells from a newer GA or alero the tunk pan on the older cars are much shallower as well but there is still a few inches to spare with the strut bolt and everything
the only thingi am worried about is the fact that the 88 may ride like a friggin 4x4 hieght wise im just not sure yet i haev a set of front and rear shock/spring strut combo with brakes at my disposal thank god i work for a huge body shop lol

the only major PISS off with the newer wells i can for see is it will screw up the design i had for the 6 point cage but that can be redrawn i suppose, i totally planned on making my own control arms useing what you described only with cromoly tubes for strength and weight saved

[Quasi Mofo]

If you are installing the inner fenders you can predetermine the ride height easily. Also consider narrowing the N body subframe AND making your adjustable moly arms, this way you get a proper geometry AND adjustability... not to mention strength.

Also get a Stock Car Products catalog and look at their heim ends and their "tie rods"

The tie rods can be bought anywhere from 2" to 40" and tapped at both ends for the rod ends... instant control arms!

[Quasi Mofo]

http://www.stockcarproducts.com

[Quasi Mofo]

http://www.stockcarproducts.com/susp9.htm
6" to 24" in aluminum

[Quasi Mofo]

http://www.stockcarproducts.com/rodend1.htm

[speedvisioncavalier]

Quasi Mofo, you are actually thinking up the same stuff i am. i already had a beat on those, but hadnt finished working mine out. i was gonna show you guys all how to do 'em. oh well, cat is out of the bag.

[89lxstanger]

more or less exactly what i have planned fuly adjustable etc
i will also make a set of caster camber plates while i am at it!

[89lxstanger]

anything come of this yet for anyone?

i have come accross a complete alerp at my work that i can strip and take more or less anything i need:banana:

[speedvisioncavalier]

take the whole rear suspension, and follow the instructions.

[89lxstanger]

here is a question?

will the springs from a jbody fit the struts from the GA/alero?

the only set back i am forseeing is the suspension itself, i am not a millionaire so i cant buy everything. any suggestions as to what springs/strut combo to go with, i looked at the alero today and i might beabel to rig up somthing for the front struts to work but i am unsure until i get it home(minus 30 with wind today) not gonna be geting it any time soon! also if i use the springs from a newer n body (eibach is the only one i am even considering) what will that do with the heavier spring rate?

any thoughts would be grand getting the rear end it gonna be a sinch the front is what worries me cause iwould like matching suspenion not multiple cars making it work!

[speedvisioncavalier]

the 3rd gen Jbodies have a similar pillow ball mount in the rear as the late model N body rear struts. once you find one in the junkyard, you will see what im talking about. thats why putting the IRS into 3rd gen Jbodies is so easy. the pillow ball mounts are about identical.

however, the older J/L/N had separeted springs and shocks, so you will have to modify your shock tower to accept a strut. you could do this by cutting out the top of your shock tower, and install a camber caster plate (like a mustang has up front), and then modify the top of the strut to be able to connect to that.

[89lxstanger]

well the rear inner wheel wells are rotten on my GA i am swapping a set of 03 j body innner wells so the whole inner wheel tub will be that exactly of a 3rd gen J. i was thinking about what i wrote today and though it might not makes the point i was aiming at..

here is a better try!
i pretty much have no choice but to use struts from a newer n body in the rear that i am fully aware of! but what can i do for the front? i dont want the heavier strut from a new n bod in the rear and a stock strut for my 88 up front!
i am gonna do the brake upgrade so bolt patterns match etc.

for the rear i am using tokico or kyb AGX adjustable struts with eibach springs, but in the front i am not sure what to do to match the rear, i cant affordto buy two sets of eibachs then mix and match. any idea to adapt a front strut from a 99 n body to the 88? or will the 99 spring fit in the 88ish strut? that is where i am lost

[speedvisioncavalier]

i can understand you wanting a good handling car. however, its actually beneficial to have softer fronts and stiffer rears. this will help the car want to rotate in an autocross type situation.

my suggestion would be to use the V6 Z24 front struts and springs (or really any V6 equipped J/L/N that has the high steering rack). they are made to hold up the heavier motor of the V6 compared to your quad. if you find the front sway bar from a GTZ or something, you should be fine cause that bar wont hit the exhaust pipe. this in the fron will give you a decent base to work from.

then you can just tune the rear of the car to make it over or understeer more. little more swaybar if you need it to start to oversteer more, and vice verse.

[89lxstanger]

so basically i am not gonna be able to get around mixing and matching!
the car should handle pretty good i am sure with the suspension i would like to go with it will be fully adjustable including cromoly control arms with hiem joint.
will 3rd gen jbod front suspenion go into the 1st gen n bod? i may have to go see for myself but we have so much snow and it is way to cold to be diggin outside.

i maye end up getting custom springs made i think. i would be easier ill have t oget a quote for two rear springs to fit a 99 n body and two fornt for a 88 n body then i can adjust the spring rate accordingly. i prefer to use the eibachs do the awesome warrenty but it is not looking like this will work in my favour of buying one set of eibachs to fit the car!

ill ynak out a set of front suspension from the alero and see if i can make it work that would be better but ti depends on what it entails!

[z24z24]

Speedvisioncaviler you talked about mounting a grand am rear suspention but what about doing a front hub/spindle swap to add grand am or caddy front back

[89lxstanger]

exactly what i am doin!

[z24z24]

post correction back to brakes lol my bad

[speedvisioncavalier]

Originally posted by z24z24
Speedvisioncaviler you talked about mounting a grand am rear suspention but what about doing a front hub/spindle swap to add grand am or caddy front back

sorry, but i dont understand your question.

[z24z24]

how to put it in lamen trems i want to put larger brakes off a 2000 grand am on to my 2000 cavalier which would aslo solve the problem of two different of bolt paters for the people doing the rear suspenion swap. You provided suck good info on the rear swap tought you might have some ideas about what im looking todo.

[89lxstanger]

in this section, under big brake upgrade he did an excellant write up on how to swap over biger 11 1/4 in front braeks fro ma caddy :banana:

[89lxstanger]

the half in spacers, now are they only there to clear the spare wheel well or is there a real purpose, i wont haev the rear suspension till the coming weekend at the earliest but i was just wondering if that is what it is for. the spare wheel well on the alero looks differant but everything else looks very similar

[speedvisioncavalier]

the half in spacers was to place that subframe(that the lower control arms attach to) lower on the frame of the car. thats about it. just thinking out loud here, if you didnt add them in, your lower control arms wouldnt be at the correct angle.

[89lxstanger]

ok i was just wondering. if it was to just clear the spare tire i would cut out metal spacers are easy though so no big deal either way..

[SpdRcrZ]

Great info - write up....... also in the works for my '02 Z24..... Its nice to see words put to the ideas I have in my head, and what I've heard floating around....... now if we only had some pics.... :)

Couple of Adj. parts for the W-body rear suspension..... not sure about the compatability of the w-n body parts...... still have to check into that. W-body parts (http://www.heldmotorsports.com/MonteCarlo.html)

As for the 'spacer blocks' if someone can mock one up out of wood, I have a machine shop that can make these for us, pretty cheap. I have to pick up my rear suspension yet, but if I dont get a mock up by then, I'll make one, and have them made.

[SpdRcrZ]

I measured the rear....... on a stock 3rd gen J-body, the rear wheels sit in 1" compaired to the fronts (measured from fender lip, to tire) When I get mine ready to bolt in, I'm NOT going to cut the rear arms, so I double check this. I hope I get this taken care of soon, I still need to pick up the rear suspension (have yet to find a complete unit in a junk yard)

:banana:

[zeroburn]

I have tried looking for kyb's and koni's for the grandam alero and have found only kyb gr2's for the rear. Does any one know if there is something that can be used besides these for performance?

[SpdRcrZ]

only thing I've found as well

[zeroburn]

I know mantapart sells bilistines for the rears but that is very pricey, but it maybe the only solution.

I wounder what kyb agx's in the front and kyb gr2's in the rear would be like?

[2K SE]

You are only gonna find gr2 for 99+ n body, or Monroes. Pretty poor selection I think. After reading spacecadet's write up on the strut inserts I was hoping there would be something we could do for better suspensions. Steph did not know of an aplication for the N body using Koni's but I would think something could be modified to fit and work right. If I can find out any other info I will
post or maybe others could post if they get any good info.

[SpdRcrZ]

next time I go to the yard, I'll pull a strut, and walk around compairing them to others....

Maybe I'll find a popular import that uses the same style

[2K SE]

SpdRcrZ
Spy really needed to talk to you about his reflash. If you haven't contacted him yet give him a shout.

And thanks for offering to go to the yard. They won't let me wander around at Jantz but I have been back there with a tech and if I could have an hour in there.....

[zeroburn]

http://www.j-body.org/forums/read.php?f=3&i=91525&t=91525

A guy posted a how too with pictures. He took the inch off the arms though.

[ragefear]

http://www.j-body.org/forums/read.php?f=3&i=101185&t=101185#101185

http://www.j-body.org/forums/read.php?f=3&i=91525&t=91525#91525

Mostly for the J owners but just incase no one has seen this just yet.

Scott

[Iboc_C64]

So, what, you guys are saying here that it may be possible to modify my 97 grand am GT to have independent rear suspention? THAT WOULD BE KILLER! Right now my only friend with a better faster car than me has a 2002 Impreza Outback Sport, he woops my ass with his IRS and AWD. Hmm, I might be able to get a little closer to him on these back roads with IRS.... hmmmm pondering, pondering... lol