v1 to v2 rear cradle swap

38153 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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StealthV

· #81 · Jun 30, 2008

Seems the shocks are doable. They don't need to be integrated with the chassis controller for V1. Simply flip the "launch" mode toggle switch on the dash. Just need to figure out the trigger signal voltage. And that part is easy with a service manual.

The '09 update is the classic cost/value trade off. And yet another opportunity for GM Performance Parts to offer a factory blessed, DIY weekend bolt-on kit.

heavymetals

· #82 · Jun 30, 2008

Yeah I look forward to them dropping the ball on this to. :yup:

StealthV said:
Seems the shocks are doable. They don't need to be integrated with the chassis controller for V1. Simply flip the "launch" mode toggle switch on the dash. Just need to figure out the trigger signal voltage. And that part is easy with a service manual.

The '09 update is the classic cost/value trade off. And yet another opportunity for GM Performance Parts to offer a factory blessed, DIY weekend bolt-on kit.

lollygagger8

· #83 · Jun 30, 2008

Bet those magnetic ones will be a pretty penny!

NormV

· #84 · Jul 1, 2008

The C5 corvette(and C6 as they are using stronger C5 axles) uses the same number of splines as the V on the outer or hub side . This allowed me to bolt up C5 hubs on my V along with BMW wheels. The axle shaft diameter is identical between the C5 & V. Not sure about the number of splines into the diff.

Norm

StealthV

· #85 · Jul 1, 2008

2

Just went and snapped a photo. If my count is right (where I my bifocals?) it's a 27-spline on the diff side.

Ja, ja, but what's the diameter?

The battery is dead in the calipers and I'm not digging out the old school version tonight (see bifocal note above).

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dvd_supercaddy

· #86 · Nov 9, 2008

Any Updates? This is a huge and important thread

UnsafeAtAnySpd

· #87 · Dec 15, 2008

Anything new on this?

Cadillac Tony

Discussion Starter · #88 · Dec 15, 2008 (Edited)

Luke and I spoke just the other day. I'm getting two CTS-Vs tomorrow (2009 models), at which time I'll be snooping around underneath them during the PDI process and comparing the length of the driveshaft and bolt pattern on the flange that bolts to the rear with a Gen.1 CTS to see if that's reusable.

As discussed earlier, the parts that will absolutely be necessary for this to be "bolt on" are the fuel tank, rear cradle, diff itself, new axles and a modification to the upper spring mounts for the rear. The driveshaft is still a question mark, and having custom axles made will definitely be the way to go (as opposed to replacing the hubs/rotors/wheels for the 09 parts).

I'll update here tomorrow.

smoothq

· #89 · Dec 15, 2008

Cadillac Tony said:
Luke and I spoke just the other day. I'm getting two CTS-Vs tomorrow (2009 models), at which time I'll be snooping around underneath them during the PDI process and comparing the length of the driveshaft and bolt pattern on the flange that bolts to the rear with a Gen.1 CTS to see if that's reusable.

As discussed earlier, the parts that will absolutely be necessary for this to be "bolt on" are the fuel tank, rear cradle, diff itself, new axles and a modification to the upper spring mounts for the rear. The driveshaft is still a question mark, and having custom axles made will definitely be the way to go (as opposed to replacing the hubs/rotors/wheels for the 09 parts).

I'll update here tomorrow.

You and Luke are Da man...

Naf

· #90 · Dec 16, 2008

This woud be interestin...I know the new diff has more bolt points for better stability. Versus one that we have now...

It may be worth your while if you are out of warrantee and changin diffs quicker then you change clothes...

lollygagger8

· #91 · Dec 16, 2008

Cadillac Tony said:
Luke and I spoke just the other day. I'm getting two CTS-Vs tomorrow (2009 models), at which time I'll be snooping around underneath them during the PDI process and comparing the length of the driveshaft and bolt pattern on the flange that bolts to the rear with a Gen.1 CTS to see if that's reusable.

As discussed earlier, the parts that will absolutely be necessary for this to be "bolt on" are the fuel tank, rear cradle, diff itself, new axles and a modification to the upper spring mounts for the rear. The driveshaft is still a question mark, and having custom axles made will definitely be the way to go (as opposed to replacing the hubs/rotors/wheels for the 09 parts).

I'll update here tomorrow.

Man that's a lot of $hit to be changing.....but I hope it works!! Good luck mang!

lunarx

· #92 · Dec 16, 2008

When looking at that 09 V, could you see if the front hubs, brakes & rotors are also interchangeable?

nmaier2201

· #93 · Dec 16, 2008

My dealer is getting 3 in this week. All are "spoken for" already. I can always "stop by" with a camera and measuring tape if it will help out... I wish I could be more of a help, I feel helpless, worthless, and hopeful. I know there are a few forum members that took delvery of an 09 V we can pry tap them on the shoulder for some info if needed.

I would be also interested in hearing an update from Luke on the "sourced custom axle shafts" I think that's the key on making this easier and more affordable. It's exciting now that the V2 is becoming available.... I'll have to start watching the junkyards as totalled ones are soon to be showing up!

CTSV_Rob

· #94 · Dec 17, 2008

lunarx said:
When looking at that 09 V, could you see if the front hubs, brakes & rotors are also interchangeable?

IS she running yet??

I need to talk with you about a clutch, maybe one in my future soon.

smoothq

· #95 · Dec 17, 2008

nmaier2201 said:
My dealer is getting 3 in this week. All are "spoken for" already. I can always "stop by" with a camera and measuring tape if it will help out... I wish I could be more of a help, I feel helpless, worthless, and hopeful. I know there are a few forum members that took delvery of an 09 V we can pry tap them on the shoulder for some info if needed.

I would be also interested in hearing an update from Luke on the "sourced custom axle shafts" I think that's the key on making this easier and more affordable. It's exciting now that the V2 is becoming available.... I'll have to start watching the junkyards as totalled ones are soon to be showing up!

Deffinatly wouldn't hurt to know measurments.

lonestranger

· #96 · Feb 7, 2009

Tony;

Let me know if there is anything I can do to help with this VITAL project - as others have said,(to paraphrase) " really no point in other mods when the stock LS6 is already too much for the present diff package etc." I am in Bradenton, FL, retired, and my 05 V is just out of warranty! Time to fix it right!!:lildevil: Seriously, I have done a lot of "wrenchin" on all types of racecars and would welcome helping you and Luke with this project.

Best Wishes;
Lonestranger
(941) 932-5355 = cell #
[email protected]

rand49er

· #97 · Feb 7, 2009 (Edited)

lonestranger said:
Tony;

Let me know if there is anything I can do to help with this VITAL project - as others have said,(to paraphrase) " really no point in other mods when the stock LS6 is already too much for the present diff package etc." I am in Bradenton, FL, retired, and my 05 V is just out of warranty! Time to fix it right!!:lildevil: Seriously, I have done a lot of "wrenchin" on all types of racecars and would welcome helping you and Luke with this project.

Best Wishes;
Lonestranger
(941) 932-5355 = cell #
[email protected]

WHOA! Here we go! Tony!

If you guys could get a firm handle on the specific steps needed to do this plus get a firm line on all the parts including part numbers, etc, ... enough to do an FAQ-worthy set of instructions, this would be very well-received. Seriously, though, it would be great to refine this conceptual remedy into a concrete set of steps and bill of materials to do this. Lonestranger is making a great offer with his assistance.

THIS PROJECT L-L-L-I-I-I-V-V-E-E-S-S !!!

Cadillac Tony

Discussion Starter · #98 · Feb 7, 2009

I'm going to be in the doghouse for saying this, but I just simply haven't had the time to go any further with the research. (ducks flying tomatoes) :duck:

As a former first Gen V owner and car nut, I definitely feel everyone's (differential) pain, but the shop has been overflowing with business lately and there's little tolerance for a nosy Salesman taking up two lifts to tinker with a V. There's also the slight issue of disassembling a brand new 2009 before selling it to someone so we can experiment- not gonna happen.

Lonestranger's offer is awesome, and it provides one of the pieces to the puzzle: A Gen 1 V. Unfortunately, there's several other pieces:

-Someone is going to have to be the person to order and pay for the parts, then deal with their car being down for an unknown amount of time while everything gets figured out. There will be speedbumps and unforseen parts needed- that you can count on with any project like this.

-Work will need to be done to the upper spring mount. How much, I don't know (and neither does my guy at GM). More parts may need to be bought or made at that point of the install

-The axles probably can't get made until someone has one of each (old and new), in hand to provide to the axle builder. I don't know if Luke ever nailed someone down to do that part.

-Ditto on the driveshaft. Now that this has been brought back to the front of my brain (thanks guys), I'll see on Monday if the Parts computer lists the dimensions for the driveshaft. I'd bet just about anything it's different.

Quite frankly, it's more of a job for a fabricator/speed shop than a Dealer. Most Service Managers won't let a Tech ignore customer/warranty work long enough to devote real time to this project, and if they did it would be at Dealer shop rates

ohnoes

.

I'll continue to do what I can on my end to gather info. Since the Parts guys shoo me away when I hang out there too long, Luke can come through with the part numbers and prices (like always), but I suspect that the final project will be done either at a speed shop or by a Dealer mechanic after hours (which means the car will be down for a while).

Boy, that sounds awfully negative when I go back and read it. :lol: There's just still a lot of question marks that won't be answered until someone bites the bullet and says "I'm going to be a guinea pig, and it's going to cost some money and time".

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heavymetals

· #99 · Feb 7, 2009

Thanks Tony.

Well if I might suggest, a case for the 09 diff could be bought then someone could work on what it is gonna take to either get that bad boy to fit or if the whole carrier is gonna need to go.

I can see one hurdle is getting it (or for that matter any other diff) to fit without having to reroute the exhaust.

Also, I think it is going to end up being too expensive, but I hope I am wrong.

rjoffe

· #100 · Feb 7, 2009

Well, I have one piece of the puzzle, I will donate one pair of V1 half shafts/axles (I have a spare set siting on the shelf) to the cause, as soon as someone is able to get a shop together, I will ship them the two axles.

There are plenty of drive shaft shops that can easily take two axles and cut and splice them for a first cut. I have priced this before and it should be in the $300 range.

Luke/Tony, does the computer provide a part number and a price for a VII Diff ?

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