v1 to v2 rear cradle swap

38155 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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61 - 80 of 156 Posts

CTSV_Rob

· #61 · Feb 22, 2008

You gonna get yourself another Gen 1 now?

Cadillac Tony

Discussion Starter · #62 · Mar 8, 2008

Two (very) minor updates on this: I talked to Luke, and he had the idea to source custom axle shafts for the rear that would bolt up to our hubs, eliminating the need to replace the hubs, rotors and wheels. The cost shouldn't be more than ordering the 09 axles, but we'll need to wait until the parts show up in the computer before we know what the spline configuration, length and diameter are. Still looking for ways to make this as easy and inexpensive as possible.

On an unrelated note, I got another email from my contact at GM telling me that they just built two "Product and Process Evaluation" vehicles (one stick and one auto) that they'll be using to further test and evaluate the final build process. He's hopefully going to be able to drive them and share his opinion, but he already said that the idle sounds really mean. He also had this to say regarding the new diff:

I have sent an e-mail regarding the fluid spec. to the engineer tasked with development of the new cast iron rear diff. I failed to ask him while he was here at LGR, but he did say that they have tried to break this new unit and have thus far been spectacularly unsuccessful, so that is good news indeed. He was very bullish about the level of robust engineering that has gone into the part and sounds totally confident.

Things are looking good for a bulletproof rear.

CTSV_510

· #63 · Mar 8, 2008

I think I speak for everyone when I say thank you Tony and Luke!

The Tony Show

· #64 · Mar 8, 2008

Edited - nevermind.

StealthViggen

· #65 · Mar 8, 2008

Flyboy said:
:wtf2:

I just mean that the 08 CTS diff and cradle has been updated already. Are we sure there is a substantial difference been the V and regular CTS? Not like There was not a difference on the first gen cars..

HiTechRV

· #66 · Mar 8, 2008

Right. Basically couldn't you mock this up with parts from an 08 CTS (say a totaled car), then swap in the V parts when available?

StealthViggen

· #67 · Mar 8, 2008

My thoughts exactly. Surely if the V2 has a better diff yet, then thats a swap, but the main problems here are the full bolt up of the cradle and associated components. The diff will just sit in there once that's sorted.

TrazzNJ

· #68 · Mar 9, 2008

:yeah:

heavymetals

· #69 · Mar 9, 2008

Hey guys, if your serious you should be talking to someone about a gas tank.

It has already been pointed out that it will need to go.

rand49er

· #70 · Mar 9, 2008

Maybe didn't read this closely enough, but if this is primarily just a diff swap (from a drivetrain standpoint only i.e. excluding the fuel tank), is there any way to provide axle shafts with substantially different torsional rigidity in order to reduce/eliminate wheelhop?

I mean, if the biggest difference is simply going to be the diff, these cars are still gonna hop like a 'roo on 'roids.

lunarx

· #71 · Mar 9, 2008

rand49er said:
Maybe didn't read this closely enough, but if this is primarily just a diff swap (from a drivetrain standpoint only i.e. excluding the fuel tank), is there any way to provide axle shafts with substantially different torsional rigidity in order to reduce/eliminate wheelhop?

I mean, if the biggest difference is simply going to be the diff, these cars are still gonna hop like a 'roo on 'roids.

It's true that the car could still hop.

However, a full 09 retrofit (mayb even a 08 retrofit) with improved diff to cradle attachment and updated half shafts, should make it much better than it is now.

Cadillac Tony

Discussion Starter · #72 · Mar 10, 2008

When talking to GM I've been working on finding out the details on a complete rear replacement- diff, axles and cradle. The new cradle brackets for the diff take the bolts vertically instead of horizonatally, which should help quite a bit with deflection under load (along with stiffer bushings). The new axles are not only stronger, but also unequal in size and torsionsal stiffness which will help reduce the oscillation that makes it hop. Finally, the cast iron diff is there and able to take the punishment when you hook, or if the road conditions happen to cause a hop (which WILL still happen from time to time, even on the best cars).

The idea originally started with the hope that we could just bolt an '09 diff into our cradle- that would have made it last longer, but still not cured the hop. Turns out that won't work, but the bright side of the extra work needed is that it will also reduce the wheelhop by changing the necessary supporting pieces.

4DoorGTZ

· #73 · May 19, 2008

Contemplating a quick fix for my newly imploded rear. Sourcing a used rear to let me drive the car this summer.

Hope to go ahead with the ''09 retrofit by...... fall/winter?

I'd be willing to drive cross continent for the work

Can I camp out in the Lindsay parking lot, as long as there's wifi and power I'm good to go! (seriously tho, anyone thought of the logistics of getting this done far away from the east coast?)

lunarx

· #74 · May 19, 2008

4DoorGTZ said:
Contemplating a quick fix for my newly imploded rear. Sourcing a used rear to let me drive the car this summer.

Hope to go ahead with the ''09 retrofit by...... fall/winter?

I'd be willing to drive cross continent for the work Can I camp out in the Lindsay parking lot, as long as there's wifi and power I'm good to go! (seriously tho, anyone thought of the logistics of getting this done far away from the east coast?)

I'm already qualifying 2 potential shops to do the work, once the parts can be purchased.
This is one mod I can't wait for. :bouncy:

zxmarekxz

· #75 · May 30, 2008

great job guys, now theres hope!!!

subscribed

heavymetals

· #76 · May 30, 2008

Should be "subscribed and supporting member".

I look at the replacement gas tank as an opportunity to:

1. Hold more fuel.

2. Access and replacement of the fuel pump (something bigger or stronger for maggie guys)

Bang for the buck, this mod sounds like it will address the major complaint and with "factory parts".

Relatively cheap.

lonestranger

· #77 · May 30, 2008

As the others had already said - You (and Luke) get a great big ATTABOY for attacking this issue so doggedly. (Just remember though, that one AW Shit, wipes out a thousand ATTABOYS!!

Seriously, great job; of course you're not done yet, don't ya know!!:bouncy: I think Luke"s idea of custom axles is the way to go, as it obviously allows us to use the wheels, brakes and hubs we have (save money for more go-fast goodies) and would also allow possibly upgrading the u-joints on the half shafts even further.(just in case a LS-7 w/122 maggie showed up at the gun fight, don't ya know!!

bpm

· #78 · Jun 27, 2008

bump

Twitch

· #79 · Jun 29, 2008

Anybody have a ballpark figure yet?

heavymetals

· #80 · Jun 29, 2008

If you peruse back a few pages, I think it was hovering between $5k-6k but they are still working on the parts list.

I don't expect it to run much more then a maggie (installed).

What I expect to add up is changing the front hubs to a five bolt to match (if we end up having to) and if that is the case, rims and different tires.

The magnetic suspension would be a neat trick to (I wish). I bet that has a lot to do with the elimination of wheel hop. Just "lock it up" and ride the throttle.

61 - 80 of 156 Posts

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