The final word on retrofitting the '09 differential

[lollygagger8]

Originally Posted by Cadillac Tony

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]

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

[nmaier2201]

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]

Originally Posted by lunarx

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]

Originally Posted by nmaier2201

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]

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!! 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 #
traveler@raths.com

[rand49er]

Originally Posted by lonestranger

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!! 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 #
traveler@raths.com

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]

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)

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 ().

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. 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".

[heavymetals]

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]

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 ?

[Rey]

Seems to me that a complete changeover to an '09 rear cradle assembly is not only very expensive, but also of little interest to CTS-V owners. The CTS-V production numbers are a fraction of Corvette, which in itself is consider quite small. Then, the numbers of those who seriously modify their CTS-Vs is much smaller yet. I suspect that all of them are active members of this forum. All this means is that it is unlikely any vendor is going to spend a lot of R&D money to produce and market this kind of modification.
What does seem more practical and doable is to adopt some of the changes made to the '09 cradle assembly - specifically the half shaft diameter changes. The differences in the '09 half shaft diameters is very important, I think. To really do the job right without a lot of engineering math, one would create two new half shafts using the same material and shaft diameters as the '09s. A less expensive change might be to just change a single half shaft on a V1, but this is more along the line of "Brute Force Engineering." Such a modification would be more reasonably priced, and much more marketable, provided it works.
At the end of the day, I do not think this mod wouild be a complete and total cure to the V1's wheel hop, but no doubt it will help somewhat.

[rjoffe]

Rey, That "less expensive change" has been discussed by many here (it's actually the reason I have a spare set of axles). However my concern is less about wheel hop (I can control that 100% with my right foot), and more about longevity of the diff. I know that my biggest concern with this car is what to do when the diff blows, I am out of warranty, and therefore will have to fork out $$$ for a new diff (V1 style). I don't believe a company will come out with a retrofit kit, rather a few of us will come up with the instructions to do it ourselves.

[rand49er]

Just like DoubleMint gum, you're both right.

Rey did hit upon one interesting point, and that is it would reasonably inexpensive do one halfshaft on a V1. Which one would be an issue (if it even really mattered), and the question wuld be how much would there be to gain ... a 2% reduction in WH (and associated improvement in the longevity of the diff) or would there be an 80% reduction. If it showed minimal improvement, then we'd know and focus elsewhere. If there was a dramatic improvement, then I'd think the market might be a couple dozen or maybe more (depending on price, of course). The experiment assessing the proposed "fix" would have to be controlled: same vehicle, same tires/pressures, same shocks, same pavement, same temps, same, same, same ... just different halfshaft.

[heavymetals]

As the prospect of any major mod like this is fast approaching over 20% of the value of the car (like a maggie), the market is shrinking.

I wish mods were tax deductible........

[ctsv154]

Instead of a whole cradle swap, just do the 09 axles, driveshaft or any one piece for that matter, and diff. If you can shove a Dana 60, 9" ford or 8.8" cobra diff in there than a V2 diff could be made to fit. Add the different size half shafts and you have helped to reduce the wheel hop and have a diff that can take the abuse if it did. Its already been said for a V2 cradle swap fabrication needs to be done so there will never be a bolt in solution. This way you dont need to buy the gas tank, rear cradle, and all that jazz. All you would need is the diff, a couple axles, and a drive shaft and a good fab shop. Everything you would need for the whole cradle swap but this leaves fewer parts to be purchased and maybe a tad bit more fabrication.

Here is another question. If you do swap tanks, will the existing sending unit be compatible with the new tank? Will we have to use the V2 sending unit and will it be compatible with the our car? Is the fuel filler in the same location? Are the straps in the same location? Are the fuel lines the same size? All this stuff would have to be figured out to do the V2 cradle swap. I say just modify the V1 cradle to accept the V2 diff and call it a day.