v1 to v2 rear cradle swap

38156 Views 155 Replies 56 Participants Last post by AAIIIC, May 18, 2022

Cadillac Tony

Discussion Starter · Feb 16, 2008

There have been a lot of questions regrading the potential for retrofitting the improved 2009 CTS-V rear setup into our cars. I've spent the last few weeks researching the issue with a lot of help from some folks at GM (who shall remain nameless unless they say otherwise), and here's the final word- the following will be easier to understand if you have a working knowledge of the terminology of what's under your car:

Yes, it's possible.

No, it's not easy.

The biggest question (or so I thought) was whether the rear subframe cradle that everything attaches to would fit. It turns out that it will bolt right up, as the GMX322 chassis has the same cradle attachment points as our 320 chassis. This new cradle has all the correct provisions for holding the new rear diff in place, as it attaches to the cradle in a completely different way than our current one.

It turns out though, that this is the easy part. According the chassis engineers, our fuel tank will cause interference with the cradle, so we'd need to swap fuel tanks. Then the upper spring seats will not be in the correct location on our chassis, which means they would have to be moved. The unequal axle shafts from the 09 use a different spline configuration than our current ones, which means they won't mount to our 6 lug wheel hubs, so the hubs and rotors would also need to be changed to '09 pieces (as well as the wheels). There's also a new driveshaft in the 09 (Dana vs. GKN), so a new driveshaft is necesssary also.

So, to recap, it looks like you'd need the following:

-Rear cradle
-Fuel tank
-Differential
-Axles
-Hubs/rotors
-Wheels
-Driveshaft
-Modify upper spring seats

I suppose if one had a connection for cheap parts through GM, it could be done for about the same or less than the KARS cradle kit, and other than the spring seats, it would be a "bolt-on" modification (albeit a severe one). This would add not only the stronger rear diff, but cure the wheel hop as well, so I'm sure there's someone out there willing to try it next year when these parts become available to order.

Hopefully that answers the questions we've all had about doing this, and if there's anything I missed please feel free to shoot me a PM.

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LUVMY04V

· #2 · Feb 16, 2008

Cadillac Tony said:
There have been a lot of questions regrading the potential for retrofitting the improved 2009 CTS-V rear setup into our cars. I've spent the last few weeks researching the issue with a lot of help from some folks at GM (who shall remain nameless unless they say otherwise), and here's the final word- the following will be easier to understand if you have a working knowledge of the terminology of what's under your car:

Yes, it's possible.

No, it's not easy.

The biggest question (or so I thought) was whether the rear subframe cradle that everything attaches to would fit. It turns out that it will bolt right up, as the GMX322 chassis has the same cradle attachment points as our 320 chassis. This new cradle has all the correct provisions for holding the new rear diff in place, as it attaches to the cradle in a completely different way than our current one.

It turns out though, that this is the easy part. According the chassis engineers, our fuel tank will cause interference with the cradle, so we'd need to swap fuel tanks. Then the upper spring seats will not be in the correct location on our chassis, which means they would have to be moved. The unequal axle shafts from the 09 use a different spline configuration than our current ones, which means they won't mount to our 6 lug wheel hubs, so the hubs and rotors would also need to be changed to '09 pieces (as well as the wheels). There's also a new driveshaft in the 09 (Dana vs. GKN), so a new driveshaft is necesssary also.

So, to recap, it looks like you'd need the following:

-Rear cradle
-Fuel tank
-Differential
-Axles
-Hubs/rotors
-Wheels
-Driveshaft
-Modify upper spring seats

I suppose if one had a connection for cheap parts through GM, it could be done for about the same or less than the KARS cradle kit, and other than the spring seats, it would be a "bolt-on" modification (albeit a severe one). This would add not only the stronger rear diff, but cure the wheel hop as well, so I'm sure there's someone out there willing to try it next year when these parts become available to order.

Hopefully that answers the questions we've all had about doing this, and if there's anything I missed please feel free to shoot me a PM.

so about 10000 dollars worth of work :thepan: haha

Im in

Cadillac Tony

Discussion Starter · #3 · Feb 16, 2008

I'd say closer to half that if you do the wrench work yourself.

BowenCT

· #4 · Feb 16, 2008

Wow, well done, Tony. Thanks for the due diligence. Who's gonna be the first?

rand49er

· #5 · Feb 16, 2008

Yeah, like Bowen said, good work, Tony! :thumbsup:

A couple of ques:

Are the splines out of the tranny the same so the driveshaft change would be just a plug and play?

Seems to me the most difficult thing here is remounting the spring perch, or am I minimizing the gas tank swap, etc.?

At around $5k, this becomes doable. I'd sell both sets of wheels (stockers and the MMs) to help pay for it, and that would open up a whole bunch of cool options for new five luggers. Probably could sell other stuff, too, like my good diff. Hmm-m ... gettin' closer to $4k now and wouldn't have to worry about a couple of post-warranty diff hits to the wallet in the future.

Again, thanks for looking into this Tony! :worship:

LUVMY04V

· #6 · Feb 16, 2008

rand49er said:
Yeah, like Bowen said, good work, Tony! :thumbsup:

A couple of ques:

Are the splines out of the tranny the same so the driveshaft change would be just a plug and play?

Seems to me the most difficult thing here is remounting the spring perch, or am I minimizing the gas tank swap, etc.?

At around $5k, this becomes doable. I'd sell both sets of wheels (stockers and the MMs) to help pay for it, and that would open up a whole bunch of cool options for new five luggers. Probably could sell other stuff, too, like my good diff. Hmm-m ... gettin' closer to $4k now and wouldn't have to worry about a couple of post-warranty diff hits to the wallet in the future.

Again, thanks for looking into this Tony! :worship:

good point!! and yeah i forgot to say good work too tony :worship:

UnsafeAtAnySpd

· #7 · Feb 16, 2008

Wow, this sounds really promising. Thanks for REALLY looking into this.

lawfive

· #8 · Feb 16, 2008

Nice.

heavymetals

· #9 · Feb 16, 2008

KUDOS.:thumbsup:

Cadillac Tony

Discussion Starter · #10 · Feb 16, 2008

rand49er said:
Yeah, like Bowen said, good work, Tony! :thumbsup:

A couple of ques:

Are the splines out of the tranny the same so the driveshaft change would be just a plug and play?

Seems to me the most difficult thing here is remounting the spring perch, or am I minimizing the gas tank swap, etc.?

You're welcome, everyone- I started researching for my personal car, and wanted to share what I've learned.

Randy, I'll send an email inquiring about the driveshaft splines on the new piece and see if it will bolt up to our T-56. If not, I think a good driveline shop could adapt it (and for that matter, adapt your current driveshaft instead of buying a whole new one).

The gas tank is a cake walk once the rear cradle is out.

dieselp

· #11 · Feb 16, 2008

Could the national highway traffic safety administration that is looking in to the diff failures force GM to recall and fit our cars with the new (safer) rear!!! It sounds like it would be a good fix for us and not crazy hard for gm. its better than gm getting sued for some one getting in an accident besause rear diff failure.

heavymetals

· #12 · Feb 16, 2008

Don't hold your breath.

Don't expect GM to do anything and you probably won't be disappointed.

Our cars are obsolete.

Get used to it.

rand49er

· #13 · Feb 16, 2008

Cadillac Tony said:
... Randy, I'll send an email inquiring about the driveshaft splines on the new piece and see if it will bolt up to our T-56. If not, I think a good driveline shop could adapt it (and for that matter, adapt your current driveshaft instead of buying a whole new one).

The gas tank is a cake walk once the rear cradle is out.

Tony, how hard/difficult would it be to alter the spring perch ... I can't recall what that looks like off hand ... are we talkin' a lot of cutting with a torch and then fitting and welding under there? ... UGH!

lunarx

· #14 · Feb 16, 2008

rand49er said:
Tony, how hard/difficult would it be to alter the spring perch ... I can't recall what that looks like off hand ... are we talkin' a lot of cutting with a torch and then fitting and welding under there? ... UGH!

Does having a Ground Control, (or other) coil-over spring perch make it easier to retrofit?

heavymetals

· #15 · Feb 16, 2008

Hey Tony,

Can the 09 shocks be adapted (ie. bolt on?)

Gonna need a computer just to talk to um.

Never mind.....

Cadillac Tony

Discussion Starter · #16 · Feb 16, 2008

lunarx said:
Does having a Ground Control, (or other) coil-over spring perch make it easier to retrofit?

I have no idea- I'm just passing along the answers to my questions as they were given to me. In the end, I'm sure there will be one or two things that no one saw coming that need to be addressed, and we won't know exactly what's involved until some pioneering soul gets hold of the parts and dives in headfirst.

The folks in several different areas of GM Powertrain and Chassis have been great for taking the time to research the information I asked for, especially at a time when they're focused on getting the new V ready for launch. I imagine that there's only so much info I can get out of these guys before someone tells me "Look- We just don't know, since we've never tried it."

Speaking strictly for myself, I'd rather spend $5k to get a bulletproof rear-end that will launch hard with no wheelhop than spend $5-$6k on mods. The gains in acceleration from this will probably make the car able to turn comparable times to a heavily modded V, but without all the tuning nightmares.

This thread was probably a year early, as it'll be at least that long before we can get our hands on any of these parts (when a new car launches, all the parts are NSA for a while for the purpose of keeping the factory rolling). I figured I'd share now so we can do a little brainstorming, and I'll keep firing questions their way until they tell me to get lost.

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Cadillac Tony

Discussion Starter · #17 · Feb 16, 2008

heavymetals said:
Hey Tony,

Can the 09 shocks be adapted (ie. bolt on?)

Gonna need a computer just to talk to um.

Never mind.....

Errrrrr.....no. :lol:

heavymetals

· #18 · Feb 16, 2008

For the hardcores sounds great.

Changes the rear to a five bolt so you can put some interesting size rims and tires.

And FACTORY PARTS :cloud9:

A year early?

Sounds like plenty of time to look at shocks, sways, and other things to make it work.

that will be one hell of a group buy! :histeric:

rand49er

· #19 · Feb 16, 2008

Cadillac Tony said:
... I'd rather spend $5k to get a bulletproof rear-end that will launch hard with no wheelhop than spend $5-$6k on mods. ...

... and I'll keep firing questions their way until they tell me to get lost.

You're too late on the mod spending, but on the bright side, that's all I've got left to mod anyway!

And I for one certainly appreciate that you're bordering on becoming a pest for these guys/gals. If it helps at all, tell them that they owe us, but I'm sure you've already used that one.

Can't say it enough: THANKS, TONY!!!

heavymetals said:
... that will be one hell of a group buy! :histeric:

:highfive:

lunarx

· #20 · Feb 16, 2008 (Edited)

Rand is right, that almost is the only mod we have left.
If we can have the improved drivetrain of the new V in our lighter chasis with similar or better WHP :cloud9:

I was already eying the 09V brakes and hubs, so I don't mind them bieng part of the plan.
I'm mostly glad to hear they will fit.

I'm thinking the spring perch relocation will just be a matter of an offset bracket with something similar to a Ground Control adjustable spring seat integrated into it.

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