Corvette independent rear suspension?

[MyCreation68]

Hey guys. I've been looking at independent rear suspension systems for putting into my dart, and I found a set from a 1981 Corvette that is for sale, it's kind of different because it uses a trailing arm instead of a control arm and a leaf spring instead of a coil spring(I'd change that to an air bag)

Anyone have an opinion on how this would work. I know they vette's were track starts so who knows maybe it'd be a nice setup?

[69DartW250]

I can tell you from experience that in order to make that IRS dependable, it will cost you close to $2000. Notice I did not say strong, just dependable. Tom's Differentials can make it strong.
The 63 through 79 Corvette used a different upper crossmember that would be easier for you to install in your car. Also, the pre 80 Corvette used a steel spring. GM switched to a composite spring for the 80 model year. It is OK, but it does NOT like heat.
I don't see where you would be able to mount an airbag under there to replace the transverse rear spring, but I assume it can be done.
Running an exhaust system on you car could be a challenge as well. The pipes on the Vette run UNDER the diffy, and the mufflers are the last part of the system. I dunno if there is room under your car for the mufflers at the tail. Also, they're Vette only pieces.
I would shy away from this idea only because it will cost a bundle for it to work properly.
GM bolt pattern is 4-3/4 X 5.
Hope this helps.

George

[MyCreation68]

I was thinking I'd mount the air bags on top of the trailing arm and remove the spring completely. Which would make room for the exhaust but I figured I could fit that above the diff.

[satellite65]

What about Jag IRS?

[MyCreation68]

$$$

[NYrr496]

Wasn't that you in the other thread that wanted to put the jap car running gear in a Dart? 

[MyCreation68]

yeah I was considering it. I know there was someone else to. but I have a slant to build. Just weighing my options for these systems. I know where a 8.8 thunderbird rear setup is with discs but I can't steal that suspension just yet.

[68dodge]

My wife has an 81 Corvette, with composite spring set up, the car will not spin off the line. The back end drops down and goes.

[68snewpy]

yeah I was considering it. I know there was someone else to. but I have a slant to build. Just weighing my options for these systems. I know where a 8.8 thunderbird rear setup is with discs but I can't steal that suspension just yet.

If you're considering an 8.8 get one from an explorer.  They can be had dirt cheap and have 31 spline axles, good gear ratios, disc brakes '95 and up, most have trac lok diffs and they are 5 on 4.5 bolt pattern.  Down side is they are 2 5/8" too wide for an A-body and the diif is offset too far.  Just get an extra passenger side axle and take 2 5/8" out of the drivers side axle tube, weld on some perches 43" apart and bolt 'er in.

[rjsjea]

You have a lot of crazy ideas for this car......what are you intentions or goals for it??

You gonna do the slant6??  bag it?? road course handling??

Im not knockin you at all, just curious where you are at?? 

[MyCreation68]

yeah I was considering it. I know there was someone else to. but I have a slant to build. Just weighing my options for these systems. I know where a 8.8 thunderbird rear setup is with discs but I can't steal that suspension just yet.

If you're considering an 8.8 get one from an explorer.  They can be had dirt cheap and have 31 spline axles, good gear ratios, disc brakes '95 and up, most have trac lok diffs and they are 5 on 4.5 bolt pattern.  Down side is they are 2 5/8" too wide for an A-body and the diif is offset too far.  Just get an extra passenger side axle and take 2 5/8" out of the drivers side axle tube, weld on some perches 43" apart and bolt 'er in.

an 8.8 from a thunderbird is an independent rear setup 8.8 from an explorer is a solid axle not where I'm headed.

You have a lot of crazy ideas for this car......what are you intentions or goals for it??

You gonna do the slant6??  bag it?? road course handling??

Im not knockin you at all, just curious where you are at?? 

Yeah road course handling with air bags so I can tune it as I go and I can drop it to the weeds. the slant is to be different everyone runs a V8 whereas I'm going to run a likely twin turbo'd slant. I want to do a 6 speed trans behind the slant but the first plan for the engine and trans will be a souped up 79 slant 6 connected to a t-5.

[rjsjea]

Are you in the planning stages or starting??? 

Looking forward to progress as you go....I wonder how the suspension will handle on a road course or on the street

[MyCreation68]

I already have it all planned out I just saw this ad for corvette parts and figured I'd check it out and see if they might be better. I'm in the teardown stages of the car I need to get it blasted before I start cutting. Once it's blasted frame connectors go in and those will be special the normal connectors and a nascar style "x" connector, then hopefully I'll have the money to buy a set of bills tubular upper control arm and a pair of air bags for mockup. then I can build my inner fenders and support braces for the air bags.

[Nitrous340dart]

There is a 69 dart in my town that I see driving every blue moon or so, it has a real low stance and I from the looks of things it had a IRS set up.... so its been done before

[loiq]

The C3 IRS (68-82) is virtually the same as the C2 (63-67) IRS and isn't the greatest design for handling.

[mischiefdart]

I would use Bill's rear set up. IRS is overrated. A properly set up live axle will handle just fine.

[MyCreation68]

I dunno something about an IRS 68 dart would be cool. Plus it just looks so darn cool.

[golferjohn]

can't disagree, IRS looks bada$$   I have Bill's rear-end (no jokes here please) and I couldn't be happier with the performance and tunability



Keep-up the good work and creative ideas, you will inspire many to think "outside the box"...(I hate that effing expression)

Later, J

[MyCreation68]

can't disagree, IRS looks bada$$   I have Bill's rear-end (no jokes here please) and I couldn't be happier with the performance and tunability
Keep-up the good work and creative ideas, you will inspire many to think "outside the box"...(I hate that effing expression)

Later, J

well I like taking the best of worlds and combining them.

[Adam]

I've driven my share of late 70s/early 80s Corvettes at work and let me just say I don't like how they handle. With an auto, put it in gear and the rear squats down like the car is trying to take a crap.

Just my opinion. Not trying to rag on anybody's machine.

Adam

[b569rr]

How strong are they? My brother just blew up the stock IRS in his "04 Cobra with only 473 RWHP.

Tom

[MyCreation68]

How strong are they? My brother just blew up the stock IRS in his "04 Cobra with only 473 RWHP.

Tom

not to sure. it's the same rear as an 8.8 solid axle but it's just the center section. Should be good stock up to like 500 hp? It'll only be behind a turbocharged slant six and on a roadcourse not a drag car.

[Bill_Reilly]

Strength won't really be a concern for you, and if so, there's alot of aftermarket stuff to make it bullet-proof. The biggest issue with irs is ride height.  Looking at the pics above, but I'm not sure what kind of car it's on.  The spindle centerline needs to be just a few inches below the frame rails. Down any further and a decent tire will have the car up like a 4x4. It's common to mock things up with stock tires, which are all around 24", and barely hit a decent ride height. Then you pick up some good 27-28" tires/wheels and discover the car is way too high and cannot be lowered enough to work out. This is especially important if you're planning on air ride.

Heidt's rears are easy to do in musclecars because they have no upper control arms - the half-shaft is the upper arm, so you can install it much higher in the car without hitting the stock frame rails.

Also notice the lower member reaches around to the stock leaf spring mount - can't do that in a mopar unless you run a bicycle tire. It looks like the car pictured won't be able to run any decent tire size either.
And last thing I can comment on - IRS systems are normally installed for good handling and street manners - a glass-smooth ride is the primary use for it. In a nice cruiser like that, side-exit exhaust noise gets annoying real quick.

Just some thoughts for you to ponder while you're planning...

Pick a tire size first and design around it. Ponder the exhaust noise to decide if you really can deal with side exit on the interstate and if not, make sure to design in exhaust routing. 6" of total wheel travel will handle the rough roads - less than 5" of total travel will knock your eyeballs out when you hit a pothole.

And just some thoughts on cost. If you change the track width, narrowing stock half-shafts is not allowed - they are induction-hardened and should not be cut. You need to have a new set of axles made - expect $500 to send out the half-shafts and get them back properly narrowed.
  Stock IRS systems can not handle a whole lot.  Take this engineering comment on the 90's Camaro - "The trans and rear axle are made to handle 250ft-lbs of torque. They will not break in operation because the OEM tire size will spin, or the clutch will slip, before you break the hard parts."  If you put sticky tires on it, breaking the half-shafts is more likely, so in that case you should do chrome-moly shafts, which are around $1000-$1200 a set.
  Tom's comment above is accurate - The Driveshaftshop is very busy shipping sets of $1200 half-shafts to Cobra owners.

IRS is cool stuff, but make sure to think about everything while you're designing - after it's built you're kinda stuck with it.

[loiq]

A bunch of the C4 guys run either Denny's halfshafts or they get their stuff cryo treated.

[MyCreation68]

Strength won't really be a concern for you, and if so, there's alot of aftermarket stuff to make it bullet-proof. The biggest issue with irs is ride height.  Looking at the pics above, but I'm not sure what kind of car it's on.  The spindle centerline needs to be just a few inches below the frame rails. Down any further and a decent tire will have the car up like a 4x4. It's common to mock things up with stock tires, which are all around 24", and barely hit a decent ride height. Then you pick up some good 27-28" tires/wheels and discover the car is way too high and cannot be lowered enough to work out. This is especially important if you're planning on air ride.

 Heidt's rears are easy to do in musclecars because they have no upper control arms - the half-shaft is the upper arm, so you can install it much higher in the car without hitting the stock frame rails.

Also notice the lower member reaches around to the stock leaf spring mount - can't do that in a mopar unless you run a bicycle tire. It looks like the car pictured won't be able to run any decent tire size either.
 And last thing I can comment on - IRS systems are normally installed for good handling and street manners - a glass-smooth ride is the primary use for it. In a nice cruiser like that, side-exit exhaust noise gets annoying real quick.

Just some thoughts for you to ponder while you're planning...

Pick a tire size first and design around it. Ponder the exhaust noise to decide if you really can deal with side exit on the interstate and if not, make sure to design in exhaust routing. 6" of total wheel travel will handle the rough roads - less than 5" of total travel will knock your eyeballs out when you hit a pothole.

And just some thoughts on cost. If you change the track width, narrowing stock half-shafts is not allowed - they are induction-hardened and should not be cut. You need to have a new set of axles made - expect $500 to send out the half-shafts and get them back properly narrowed.
  Stock IRS systems can not handle a whole lot.  Take this engineering comment on the 90's Camaro - "The trans and rear axle are made to handle 250ft-lbs of torque. They will not break in operation because the OEM tire size will spin, or the clutch will slip, before you break the hard parts."  If you put sticky tires on it, breaking the half-shafts is more likely, so in that case you should do chrome-moly shafts, which are around $1000-$1200 a set.
  Tom's comment above is accurate - The Driveshaftshop is very busy shipping sets of $1200 half-shafts to Cobra owners.

IRS is cool stuff, but make sure to think about everything while you're designing - after it's built you're kinda stuck with it.

What do you suggest on what I plan on doing Bill? I want to be able to set the car down on the frame But i think the law is going to change regarding what I do to the car ie modifying the frame so I may have issues with clearencing. I'm planning on running tires that are only about 24" tall and hopefully as wide as possible. I like those heidt's rears but 5K is pretty high for me. Maybe your Street Lynx setup would be better for what I want to do?

[golferjohn]

 
A properly tuned live axle will handle as well and have less breakable parts IMO

[MyCreation68]

A properly tuned live axle will handle as well and have less breakable parts IMO

Yeah, An IRS would be cool but I'm not sure if I can do what I want with it.

[Bill_Reilly]

There's nothing easily possible that will put the frame on the ground outside of a full-chassis build and put your body on it.
How about if you did a more conventional build and added 4 of those little indy car jacks under the car? Instead of dropping the car for security, have a button to pick the wheels off the ground instead?

[MyCreation68]

hmm now that sounds interesting, I'll look into that to it would probably be a ton easyier to put those on then try and make the air bags so I can drop it.

[jamesdart]

i know the mustang crowd was pissed when the put IRS in the cobra. bill what 90s camaros have irs?