# C5/C6 Vette IRS transplant to 67 GTO



## tapps33 (Jan 11, 2012)

I would like to reach out to one and all on the forum for some advice/guidance/help etc... I recently purchased a 67 GTO convertible (due to be delivered late Feb 2011) and have already begun planning my upgrades and modifications. The biggest mod I'm planning is to transplant a C5/C6 vette IRS into the GTO. Has anyone ever successfully accomplished this? I know someone's been working a newer GTO IRS into a chevelle frame, and someone put the whole thing into a Gen 1 camaro, but I haven't really been able to dig up any info on vette IRS transplants into A-frame's. 

Before everyone starts chiming in on whether IRS or solid axle is better, I'd like to limit this thread to information only, I don't want this thread to turn into a "what's better discussion." I've been planning my GTO for quite some time, (my dad recently sold his 65 GTO convert....not to me BTW), and I'm pretty much sold on IRS. I'm not planning on dragging the car, just want it to be a very fun weekend/daily driver that'll carve the curves up much like a new vette. 

Now that the business is out of the way, let me detail my plan so you guys can chime in and tell me where my estimates are wrong....

I've been looking at different IRS systems, and I like the C5/C6 vette's the best. (I have read the cobra IRS had some diff support issues, I don't feel like fabricating everything needed for the C4 vette rear ends, and the newer GTO IRS supposedly wasn't nearly as good as the vette IRS.) That being said, as best I can tell, in order to mount the C5/C6 IRS obviously I'd need to create mount points for the lower IRS subframe, as well as weld in a cross member for the top diff support. The biggest issue IMO is i'm going to have to calculate where/how to mount the upper control arms. Then create or buy an adapter plate to attach my drive shaft to. I don't want to modify the GTO to fit the rear mounted vette transmission....not to mention the GTO already has a 5 speed TKO600 installed in it. I don't want to cut into any original metal unless I absolutely have to. 

What am I missing? I have this inkling that there might be some computerization involved to deal with the differential LSD or something? I know the width is going to be different than the stock axle, but I was already planning on swapping the wheels out for some Boyd PT-01's. (probably 9" wide in the rear...potentially 10" if I can get them to fit without major modification...aka without hitting the frame rail) Theoretically as long as I calculate the rear wheel dish correctly everything should work out ok....

Am I over-simplifying the transplant process? (I have a habit of doing this all the time....just ask my wife) 

Any help, advice or guidance would be greatly appreciated! I'm trying to ensure I plan everything out before I start the project, especially since I'm already starting to scope out a rear ends for the transplant. 

Thanks,
Chris


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## motoristx (Apr 27, 2010)

I've seen a 56' Corvette done like this, but is was set on a modded rolling chassis of an 05 Corvette. I was told his was a kit... it was Beautiful! if you didn't know what to look for you'd think its was origanal. 

Have you thought about looking for a kit like this? or I'd wonder it somone even made a kit like this.


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## AlaGreyGoat (Jul 6, 2006)

The C5 uses a rear mount transaxle directly bolted to the engine through a torque tube and uses a traverse leaf spring suspension.
Looks like a lot of wor to me.

Larru


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## tapps33 (Jan 11, 2012)

I thought about an aftermarket frame....it's actually what I really wanted to do, but given the rather large price tag associated with it I decided the stock frame will work just fine until I hit the lottery! 

As for the transverse leaf springs, from what I can discern from various drawings and pics of the IRS, the transverse spring only ties into the lower IRS subframe, hence, if I mount the subframe correctly, everything should work the way it's supposed to....should being the operative word there. Now, the transaxle size may be an issue fitting it where the stock diff would go....but since I'm getting rid of the transmission and just using the differential/transaxle, I think it'll fit...I may have to wait and when I get the car slide it up under there and see. 

Thx,
Chris


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## ALKYGTO (Mar 29, 2010)

Wow, yeah, an ambitious build but...... so much work for so little gain. Yes, I think you are oversimplifying what this endevor will take.

These cars can be made to handle pretty decent with the solid axle and with a lot less hassle. 

It's your car after all though so do what you want and have fun with it :cheers.


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## Rukee (Feb 8, 2007)

With the tranny mounting to the rear diff (much like a transfer case to a tranny with a shaft), how are you going to move it forward to behind the engine?? I could maybe see using everything~ the engine, drive tube, tranny and rear end as a whole cause it's structural, but how are you going to separate them and still have them usable?


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## Eric Animal (Oct 28, 2007)

May I suggest that you talk to Chris at Street Rod Garage They built my custom chassis, and offer "upgrades" and do custom work like you want. They also have a cool website with lots of pictures!!! Eric


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## tapps33 (Jan 11, 2012)

Rukee said:


> With the tranny mounting to the rear diff (much like a transfer case to a tranny with a shaft), how are you going to move it forward to behind the engine?? I could maybe see using everything~ the engine, drive tube, tranny and rear end as a whole cause it's structural, but how are you going to separate them and still have them usable?


I've seen a couple builds where people have used regular tranny's with their engines, then built an adapter plate that basically eliminates the transmission and torque tube from the system. (Aka it's basically an aluminum plate with a bearing carrier and a pinion yoke) 

"May I suggest that you talk to Chris at Street Rod Garage They built my custom chassis, and offer "upgrades" and do custom work like you want. They also have a cool website with lots of pictures!!! Eric"


I will definitely give them a call and visit their website, it may be there's a cost effective solution that won't require me to work for the next 5 years to install (or pay for!) :rofl:


"Wow, yeah, an ambitious build but...... so much work for so little gain. Yes, I think you are oversimplifying what this endevor will take.

These cars can be made to handle pretty decent with the solid axle and with a lot less hassle. 

It's your car after all though so do what you want and have fun with it ."

That's why I'm here, I'm constantly trying to work the cost benefit analysis part of this....it may turn out to be just too engineering intensive, or worse too cost intensive...my wife would never let me hear the end of that. Like I said, the endgame for the car is classic 1967 muscle that handles much like a newer car....but regardless, a 67 gto is still a beautiful car to look at, regardless of how she handles! :cool


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## crustysack (Oct 5, 2008)

well you can forget the cost benefit analysis, since for the rear end swap to provide any benefit the whole front end will also have to be upgraded, new control arms coil overs etc. Have you done the front already?? A complete rework of the front suspension will make the car handle 100% better. But back to topic- VERY ambitious swap, of course it CAN be done . Theres no modification time and money cant do., but there is some major fabrication going on- It may even be easier to attach the whole rear subframe assembly, that way all the suspension geometry is already figured out and you would just have to cut out a section of the frame and graft the new piece in, (for starters). I would like to see this done it would be sick- try lurking over on the pro-touring web site there are a few camaroos with this set up already


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## heyman (Jan 15, 2010)

tapps33 said:


> I would like to reach out to one and all on the forum for some advice/guidance/help etc... I recently purchased a 67 GTO convertible (due to be delivered late Feb 2011) and have already begun planning my upgrades and modifications. The biggest mod I'm planning is to transplant a C5/C6 vette IRS into the GTO. Has anyone ever successfully accomplished this? I know someone's been working a newer GTO IRS into a chevelle frame, and someone put the whole thing into a Gen 1 camaro, but I haven't really been able to dig up any info on vette IRS transplants into A-frame's.
> 
> Before everyone starts chiming in on whether IRS or solid axle is better, I'd like to limit this thread to information only, I don't want this thread to turn into a "what's better discussion." I've been planning my GTO for quite some time, (my dad recently sold his 65 GTO convert....not to me BTW), and I'm pretty much sold on IRS. I'm not planning on dragging the car, just want it to be a very fun weekend/daily driver that'll carve the curves up much like a new vette.
> 
> ...


There's a reason why the C-4 swaps are popular, the rears are plentiful, and cheap, and Much easier to swap in, and modify, seeing a couple done on local C-3 Corvettes, both did front and rear swaps. Keep it Simple, the end result, will be the same.


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## tapps33 (Jan 11, 2012)

heyman said:


> There's a reason why the C-4 swaps are popular, the rears are plentiful, and cheap, and Much easier to swap in, and modify, seeing a couple done on local C-3 Corvettes, both did front and rear swaps. Keep it Simple, the end result, will be the same.


Have many people done C4 (Dana 44) swaps into A-Bodies? If so, is there a mount kit I could buy? I found some for trucks, but not a GTO. I'd like to make life a little easier on myself and let someone else do the fabrication...less chance for me to screw it up.


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## tapps33 (Jan 11, 2012)

crustysack said:


> well you can forget the cost benefit analysis, since for the rear end swap to provide any benefit the whole front end will also have to be upgraded, new control arms coil overs etc. Have you done the front already?? A complete rework of the front suspension will make the car handle 100% better. But back to topic- VERY ambitious swap, of course it CAN be done . Theres no modification time and money cant do., but there is some major fabrication going on- It may even be easier to attach the whole rear subframe assembly, that way all the suspension geometry is already figured out and you would just have to cut out a section of the frame and graft the new piece in, (for starters). I would like to see this done it would be sick- try lurking over on the pro-touring web site there are a few camaroos with this set up already


I haven't had the car delivered yet, so I'm not sure what has or hasn't been done WRT the front suspension, however, my plan has always been to do a complete front suspension re-build/upgrade. I will probably start a thread on pro-touring and lateral-g forums once the swap starts. That being said, I have learned that most guys that are on this forum have been playing with classic muscle cars a heck of a lot longer/more than I have, and I wanted to get your experienced opinion and advice before I drop a ton of money and time, and end up breaking my car instead of improving it. 

However, in this case, money and time are definitely an issue, and I'm beginning to think I may have to put the swap on hold. I may just re-work the front and just band-aid the rear with some minor upgrades until I have enough time/money to do it right. First and foremost I'm going to try to track down a vette in a scrap yard and at least get some measurements so I can start the engineering it'll take to make the swap work.


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## heyman (Jan 15, 2010)

tapps33 said:


> Have many people done C4 (Dana 44) swaps into A-Bodies? If so, is there a mount kit I could buy? I found some for trucks, but not a GTO. I'd like to make life a little easier on myself and let someone else do the fabrication...less chance for me to screw it up.


Personally I don't know of any mount kits, it's just a matter of fabbing something up, helps if you have skills in this area. as for buying a C-4 in a scrap yard, I always just looked for a rough car, that someone is trying to sell, cheap, 85 to 87's can be had for a few grand, must be a stick shift car to have a Dana 44's (84's are cheaper, but all have Dana 36's,) plus they have 2:88first gear T-10's which are worth having.


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## crustysack (Oct 5, 2008)

although it would be sick to do the swap -its going to BIG money especially if you have to pay for fabrication work- I think you can get a very decent handling car with a traditional set up with new components- the stuff available now makes a HUGE difference over stock component- I've gone with Global West control arms up front, QA1 coil overs up front and QA1 shocks in the rear with the GW rear control arms also- all new steering components+ sway bars and my car handles very nicely. For the amount of money I spent I am very happy. The next level of course is to get a completely assembled new design frame- like a SRG but your talking 10k for starters- Keep it simple and the 1 year less of build time will be worth it


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## tapps33 (Jan 11, 2012)

crustysack said:


> although it would be sick to do the swap -its going to BIG money especially if you have to pay for fabrication work- I think you can get a very decent handling car with a traditional set up with new components- the stuff available now makes a HUGE difference over stock component- I've gone with Global West control arms up front, QA1 coil overs up front and QA1 shocks in the rear with the GW rear control arms also- all new steering components+ sway bars and my car handles very nicely. For the amount of money I spent I am very happy. The next level of course is to get a completely assembled new design frame- like a SRG but your talking 10k for starters- Keep it simple and the 1 year less of build time will be worth it


I'm not going to lie, the ideal scenario would be a brand new frame with all the new hardware built directly into it, but when I put everything together, axles, brakes, suspension etc... it keeps adding up to well over $20K. Needless to say I won't be doing that anytime soon. I think for right now what I'm going to try to do is track down some old vettes at the local junkyards and take as many measurements as I can and see if it'll fit, then maybe I'll go ahead and try the swap. Right now, the car runs and drives as it is, and I'd like to keep it that way unless I know I'm going to put a sure thing underneath the rear end. Thanks for the advice guys!

Chris


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