Hey Daniel, hope solo2 went well this year... I've got the Z off the road for some tweaking so I didn't make any this year.

I've been debating an IRS project for a while, looked into the C4 setup and didn't like the way they have the halfshafts as the upper control arms... seems like a weak setup to me. I REALLY like the C5 transaxle setup, and if I could get my hands one one relatively cheap I'd see if I could go that route... I agree with Larnach that moving the tranny to the rear would be a huge plus to the project, and would help balance enormously.

I'm thinking that such a project would be in the 5-10k range... closer to 10k if you went the rear mounted tranny route. I have no idea what a used C5 rear would cost, but I expect with the tranny you're looking at well over $3000, then figure a couple thousand to strengthen it, and thousands in custom metalwork to mount it up, including a custom rollbar (rear mounts coinciding with suspension mounting points), shift linkage, exhaust mods, drive shaft (not sure how hard that "torque tunnel" rig is to shorten/lengthen), rear engine support and lots of sheet metal work. I don't see how it could ever be a kit, I expect there'd be some radical modifications to the rear of the car required to stiffen and provide clearance. I'd definitely want to keep my ABS and Traction Control.

It would be a VERY cool mod though, I wonder what the weight distribution would be?

 

Dave! I was wondering if I'd ever see you around again Solo2 went very well this year. Skip has continued to set FTD's in his r-compounded S2000...and I'm consistently only a few tenths behind on street tires. I've managed to get a lot of events in this summer and really progressed as a driver.

A rear-mounted tranny would be...um...heaven? And I don't think would be quite as hard as you're implying. Shift linkage? C'mon...that's relatively simple, considering all the alignment is within the T-56, so we just have to match up to the outside point.

However, that's not even on the whiteboard at the moment. The project is progressing much smoother than I thought it would and I think we will see results at a point much sooner than I thought. I don't want to give hard dates, but let's just say I've been pessimistic, so "sooner" isn't a near date.

For all who are wondering... 3-channel and 4-channel ABS will be maintained. We should have absolutely no problem with that, and consider it a must. With ABS being maintained, TCS should automatically work.

And, this isn't official yet, but I think we can get it to mount efficiently without having to fabricate "new"mounting points requiring a cage.

The purpose of this project is to make it user-installable.

But once again, I make no guarantees this will succeed. We're still in the feasibility stage, we're just moving along...

So what's the tweaking on the Z? I'm dying to hear. Drop me a PM sometime.

And who knows...considering we're still in the "hand-waving" stage...I'll talk to the designer about rear-mounting the tranny. I just don't think it'll be worth the cost/effort/complexity.

Dan

[EDIT] On edit...ok, so the rear-mounted tranny would help F/R distribution, but wouldn't it actually increase polar moment? I mean, the engine is mounted pretty far back already, so the tranny starts well behind the front axle. Whereas a rear-mounted would put the end of the tranny very near the rear axle...so wouldn't that shift more weight away from the center? I don't think the F/R advantage would be worth the polar loss. Just a thought...[/EDIT]

 

Would definitely increase polar moment, but I'm not sure about the impact of the increase relative to the balance advantage... and it may depend on the type of driving (SOLO 2 or road racing).

I think overall it'd depend on how much balance would be improved and PMI would be hurt. On the vette there's a big difference in overall handling between the C4 and C5... I imagine the rear mounted tranny is a factor there (especially considering the engineering cost of making that change).

Other thing to consider is that overall weight would increase too, and that drivetrain efficience would decrease.

 

The solid axle we have is pretty damn good, I can't imagine it being worth it to swap to an IRS, unless you just want it for "pimp" appeal, and which case you probably want to do it yourself.


Fbody != vette, deal with it


youc an get a nice c4 for less than~ 10k

 

Straight and to the point. I love it. Couldn't agree more.

 

solid axle isn't bad, but I wouldn't call it good either... unless you're only interested in straight line... and even then it's not good once you have any real traction. Definitely for me there's some "coolness" factor involved... not as cool as going AWD... but that project's just a tad beyond my ability to imagine . I think the improved weight distribution and unsprung weight reduction would mean significantly better handling than a solid axle f-body in real world conditions. Sure they're no Vette... but that's why I like em! I don't like C4's (ugly imo)... so they're out. The Z06 is too expensive for the time being (maybe when the get into the high 20's/low 30's used).

 

interested

 

I could be mistaken and it has been awhile, but I remember something about a company or an individual who fabbed a really good IRS for the Fbodies but the whole kit was like $7,000. Certainly not worth it. . . Just give some throttle and induce a lil over steer

 

any update on this kit? I've got access to a 4-post lift, MIG welder, TIG welder, compressor, all the usuall...

Any chance of this being hooked up by February?

The coolest idea to me is hooking up a C5 IRS complete with T56 transaxle... might cost a fair bit to get the parts, but I can't imagine fabrication costs being TOO high.

Considering a 12-bolt fully loaded is $2500 to $3500, I'd say the C5 conversion under $5000 would be a deal.

I need to get rid of this 10-bolt by the time my 383 is ready... so lets get some updates/results!

 

I don't wanna sound the wrong way. But I think that a kit maybe too complicated, and it would be easier to just have someone fab the connection points for a C5 or C4 rearend under a f-body. A "kit" would still require enough fab skills to really occomplish the task without a kit. (at least in my opinion)

I've seen pics of two cars that's been done with a C4 rearend, and really it didn't look to bad from a fab standpoint. The hardest part will be aligning the rearend, and putting in a little extra support in the rear subframe. Also I think the gas tank might have to be relocated or modified.

I know a friend of mine was comparing the demensions of a C4 rearend to his 3rd gen a few years ago. Pretty much the shock mounts could be used, and the LCA brackets would have to be modified (but I think line up to the arms on the IRS).

I also have heard roomers of GM doing a couple of test mules back in the late 80's early 90's of 3rd gens with a C4 IRS.

 

Yeah, I was kinda thinking the same way... although with a C5 transaxle.

The way I figure it, instead of rebuilding my current T56 and buying a 12-bolt rear, and bilstein shocks... I may be able to get a Z06 transaxle for a bit more. All I need is a little reassurance that "someone" has made this work.

Removing the torquearm from the tranny tunnel will also give some room for the torque tube. The other thing to consider is the clutch assemby and how the torque-tube would attach to a LT1 engine....

all these things need to be looked at, and I was wondering if anyone's done it... even to the tune of $5000 or so. Considering you get a 10-bolt upgrade, new tranny, IRS, and a balanced 50/50 weight distribution... seems like a bargain to me.

All I gotta do is find a wrecked vette (preferably Z06) and find out who's pulled this off (because I'm SURE someone outhere has... vette parts are too common and cost-effective NOT to use).


Alternatively, I'd be happy with keeping my front-mounted T56 and using a C4 or Viper IRS for the conversion instead... although the Z06's triple-syncros and better weight distribution sound like a better deal IMHO.

Doesn't ANYONE have an IRS camaro to "cheat" off of?

 

I guess I really don't understand this desire. C4s and even C5s can be had quite cheaply now and have more advantages to them than just an IRS. I'd just sell my car and buy a Vette before I'd sink that much time into mine. Then again, I don't think an IRS is enough of a performance advantage to warrant even considering it.

Unless you buy a junkyard C5 IRS and do all the work yourself I don't think a conversion like this could be had for anywhere near $5K.

I bet if you sold your car and bought a C4 with that $5K you'd be far ahead.

 

There is more to this swap than just the advantage of having the IRS, there is the pride involved in accomplishing somehting of the sort, there is the uniquiness of it.
The C4 IRS swap has been accomplished several times in several different cars, I have multiple pics of it.
The C5 I haven't seen pulled off yet, but I'm sure somewhere someone has done it, it's just whether you can find them, or if they're even online or have pics. It would obviously require the turning of you car into a 2 seater LOL! and I can't say I haven't looked into it a little bit, it's just the parts are a little too expensive for me to get right now, and after looking into the C4 set up more and more, although it would be an improvement, there are far better IRS setups to cannabalize before that one despite the "ease" of installation.
Given that the C5s tranaxel has it's own subframe it would justinvolve welding in the subframe and getting it positioned right in relation to the resot of the drivetrain, shouldn't be bad at all really

 

Well for an LS1 car, the C5 swap with torque tube shouldn't be to bad at the motor. You may need to just shorten/lengthen the torque tube/shaft.

For an LT1, my guess would be to put a T5 (3rd Gen) type clutch with a really good slave/master cylinder setup, and of course lengthen/shorten the tube and shaft to specs.. the bellhousing should fit, at least most of the bolts should line up. Not sure on the T5 clutch clearance.

If you want to keep your LT1 style clutch, then that might be tough to do. You'd need to design a mount for the clutchfork in the bellhousing.

Not sure how it would mount to the rear of the car though... I've not looked at one next to a 10bolt from our cars.

 

In all honesty the torque tube setup in the C5 was the biggest obstacle I could come up with when Is tarted thinking about it alot, hell I don't even know how the torque tube works or what's in it, or how to find out, cause as mentioned welding in the rear subframe from the C5 shouldn't be hard really, just as previously mentioned you have to make sure it's aligned right, and while no small task, it isn't monumental either.

If I had the money and understood how the torque tube attatched to everything and how it actually functioned I'd give it a go.

The C4 set up just didn't seem appealing the more I looked at it , but it would be so nice to hit a bump with one wheel and not have the whole freakin car come unloaded. Especially when on a highspeed turn