Independent Rear Suspension - 1972 Cutlass
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Joined: Mar 2020
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From: Greenville, NC
Independent Rear Suspension - 1972 Cutlass
I have restored 5 Cutlass's over several years. Once complete, I give them to a family member. Time for me to restore a "keeper". Have been told "it cannot be done" by well meaning people multiple times over the years, I do not subscribe to such. There are several "it cannot be done" things which I am going to add to my keeper. I have no desire to purchase a new fabricated IRS from the usual suspects (Heidts, Morrison, etc.), so I am researching to determine the best donor car to swap the IRS for my 1972 Cutlass. Ideas are appreciated. Thank you.
Try a 2008 or 2009 Pontiac G8 GT rear 
Administrator
Joined: Oct 2009
Posts: 42,496
From: Poteau, Ok
A friend and I converted a C2 Vette frame with C4 front and rear suspensions. If you are a good fabricator it can be done. I would suggest a whole new frame setup if that's the route your going. The big brakes will limit you to larger wheel diameters.
Old(s) Fart
Joined: Mar 2007
Posts: 50,802
From: Northern VA
Can it be done? Of course it can. People have been doing Jag rear end swaps for decades.
Unless you have a frame jig and understand suspension geometry, I would stick to an IRS that uses a bolt-in subframe with all the pickup points built in. The T-bird is one such rear. I have no experience with the G8. Of course the added volume occupied by the IRS means that you need a custom gas tank and exhaust routing. The bigger problem is that after doing all that work, the crappy FRONT suspension geometry will still be the limiting factor. If your goal is handling, put your time and money into fixing THAT first. You'll be amazed at how well the car will handle with a proper front suspension geometry and correctly-chosen sway bars and springs. If you want the IRS just to impress the uninformed at cruise night, then do whatever you want.
Unless you have a frame jig and understand suspension geometry, I would stick to an IRS that uses a bolt-in subframe with all the pickup points built in. The T-bird is one such rear. I have no experience with the G8. Of course the added volume occupied by the IRS means that you need a custom gas tank and exhaust routing. The bigger problem is that after doing all that work, the crappy FRONT suspension geometry will still be the limiting factor. If your goal is handling, put your time and money into fixing THAT first. You'll be amazed at how well the car will handle with a proper front suspension geometry and correctly-chosen sway bars and springs. If you want the IRS just to impress the uninformed at cruise night, then do whatever you want.
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From: southeastern Michigan
Thread Starter
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Joined: Mar 2020
Posts: 10
From: Greenville, NC
Thank you for the advice. There are many talented car fabricators in my area as one would expect in North Carolina, also have a donor car with a frame in great shape, plan is to make the upgrades on the donor then swap. Fortunate to have a close friend and “retired” fabricator with decades of experience, he has frequently expressed interest in” helping” me with this particular project. He knew this would be out of my depth, now I know too. Your post is spot-on.
Thread Starter
Registered User
Joined: Mar 2020
Posts: 10
From: Greenville, NC
Can it be done? Of course it can. People have been doing Jag rear end swaps for decades.
Unless you have a frame jig and understand suspension geometry, I would stick to an IRS that uses a bolt-in subframe with all the pickup points built in. The T-bird is one such rear. I have no experience with the G8. Of course the added volume occupied by the IRS means that you need a custom gas tank and exhaust routing. The bigger problem is that after doing all that work, the crappy FRONT suspension geometry will still be the limiting factor. If your goal is handling, put your time and money into fixing THAT first. You'll be amazed at how well the car will handle with a proper front suspension geometry and correctly-chosen sway bars and springs. If you want the IRS just to impress the uninformed at cruise night, then do whatever you want.
Unless you have a frame jig and understand suspension geometry, I would stick to an IRS that uses a bolt-in subframe with all the pickup points built in. The T-bird is one such rear. I have no experience with the G8. Of course the added volume occupied by the IRS means that you need a custom gas tank and exhaust routing. The bigger problem is that after doing all that work, the crappy FRONT suspension geometry will still be the limiting factor. If your goal is handling, put your time and money into fixing THAT first. You'll be amazed at how well the car will handle with a proper front suspension geometry and correctly-chosen sway bars and springs. If you want the IRS just to impress the uninformed at cruise night, then do whatever you want.
Thread Starter
Registered User
Joined: Mar 2020
Posts: 10
From: Greenville, NC
Thread Starter
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Joined: Mar 2020
Posts: 10
From: Greenville, NC
I love my sisters, but I am honor-bound to strictly adhere to “Man Code”. Consistent with said code, I will share a brief story to sum the mindset of my sibling. Years ago, I presented a two-year project, frame-off resto ’71 Vette to my older sister, she seemed ecstatic in the moment, drove it for a few times, but soon returned to her preferred method of transportation; “broom riding”. Cannot change a Zebra’s stripes. Still want to meet any of them?
Thread Starter
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Joined: Mar 2020
Posts: 10
From: Greenville, NC
Thank you for responding. Collectively, all who responded helped me understand this should be handed over to a professional fabricator. For helping me realize this, I thank all for saving me from what certainly would have been an extremely frustrating endeavor, not to mention all the money I would have thrown at the project before eventually turning over to a pro anyway.
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