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Discussion Starter · #1 ·
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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Discussion Starter · #10 ·
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.
 

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Discussion Starter · #16 ·
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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Discussion Starter · #17 ·
Hey Tony,

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

Gonna need a computer just to talk to um.:eek:

Never mind.....
Errrrrr.....no. :lol:
 

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Discussion Starter · #37 ·
Quite frankly guys, my specialty is cars- both product knowledge and getting you a fair price on one. My sponsorship of the forum is personal, so my Parts and Service Department aren't involved. If anyone is going to put together a package for this retrofit it will be Luke and James, the fine fellows at Lindsay Cadillac.

My interest in finding this out is both personal and helping out fellow V owners, and if there's anyone qualified to take this info and run with it, it's those guys. :thumbsup:
 

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Discussion Starter · #52 ·
To everyone who's said Thank You: You're welcome. :D

My reason for researching this is partly personal, and partly for the benefit of the community. Luke and I spoke yesterday, and will again today- we're working on figuring out the most cost effective way to get this mod to the market. Obviously, there's going to be a few unforeseen issues, and the parts won't be available for a while yet, but progress is being made on figuring out the easiest way to get this done. Lindsay will be the source for the parts, although I'm going to talk with my shop foreman about the possibility of helping people in the South who are too far away from Lindsay for it to be practical (as far as installation goes).

There will probably be some periods of inactivity in this thread while we wait for the SOP on the 09 V parts, so there's no need to keep bumping this up and cluttering the forum. If Luke or I have any updates, we'll post them here as we iron out some logistics. I'm looking forward to helping make it happen. :thumbsup:
 

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Discussion Starter · #62 ·
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. :)
 

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Discussion Starter · #72 ·
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.
 

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Discussion Starter · #88 · (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.
 

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Discussion Starter · #98 ·
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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