The final word on retrofitting the '09 differential

[Cadillac Tony]

Originally Posted by lunarx

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.

[Cadillac Tony]

Originally Posted by heavymetals

Hey Tony,

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

Gonna need a computer just to talk to um.

Never mind.....

Errrrrr.....no.

[heavymetals]

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

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!

[rand49er]

Originally Posted by Cadillac Tony

... 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!!!

Originally Posted by heavymetals

... that will be one hell of a group buy!

[lunarx]

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

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.

[StealthV]

Within the first few weeks of introduction, there will be plenty of wrecked V2s to scavenge parts.

[rand49er]

Originally Posted by StealthV

Within the first few weeks of introduction, there will be plenty of wrecked V2s to scavenge parts.

[DILLIGAF]

Maybe this could be adapted to fit in our cradle?Anything special about the size of the 5 lug pattern?

[Venomous-V]

Ok, we all agree that our diff problems start with wheel hop, correct? Has anyone noticed that in all the write ups for the new V, they state that they know the problems of the current V and to help "REDUCE" and "MINIMIZE" the whell hop in the new V they are using different diameter shafts! Does this not strike anyone as odd that no write ups say it has been completely resolved? Has me wondering how much hop will be in the new one.....Guess we will have to wait and see.

[heavymetals]

It won't go away in a independant rear suspension with that much torque.

The attributes contribute to the problem.

If you want to improve it to the point where it goes away, you will almost certainly have to use a straight axel and stiff suspension and no limited slip.

In other words a straight line car.

On the other hand, Kars said his system virtually eliminated the hop.

[rand49er]

Plus, others have mentioned that MANY IRS cars display wheel hop including Porches.

[heavymetals]

Originally Posted by rand49er

Plus, others have mentioned that MANY IRS cars display wheel hop including Porches.

Also, the more HP you add to the equation the more likely it's gonna happen.

Those magnetic shocks are looking good right now.........

Let's see...

Pick up the G force from the computer and any other info, add an accelerometer, strain guages, and get some software and hardware together.

I would guess about $25k might cover it (less the shocks).

Those magnetic shocks ain't looking so good

I need a beer...........

[ZEUSROTTY]

wHY DO ALL OF THIS? Didnt you say the CTS-V doesnt have a diff problem? LOL... Just kidding!!! Doesnt seem like it would be that hard. Custom gas tank would be the tough part.

Originally Posted by Cadillac Tony

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.

[V-Love]

I am starting to like Tony!!! I GUARANTEE someone will do this. It won't be me but as our cars get older and out of warranty, it will happen. Awesome post Tony.

[StealthViggen]

Why are we focusing on the V2 parts? Has the 2008 cts not been revised? i am sure there are plenty of those available wrecked now.