: Differential ratio swap to a 3.42 or maybe 3.23 on 2004 CTS-V. Need input.

04-01-11, 04:19 PM
I know the short 3.73 gearing is better for performance, but to be honest, I never track the car or race it. I bought the V because I needed a 4 door car, and wanted a manual transmission, at least 300hp and rear wheel drive. I love the feeling of tons of power available any time I want, but unless I race it, first gear is way too short. I find myself taking off in second almost always. My question is can I swap an entire differential from a 2007 SRX with limited slip for the stock one without having to open it up? Is it a simple bolt in deal? I say SRX because I figure the half shafts may be the same since both the CTS-V and the SRX have 6 lug wheels. I would also consider the 3.42 found on the regular CTS, but from my research, I may have to replace the half shafts and hubs/rotors/wheels etc... and I don't want to do that. Has anyone done this swap? I assume fuel economy would also be considerably better with the 3.23 vs the 3.73.

04-01-11, 04:44 PM
Gee, I think if I were going to go that far, I would just do the Creative Steel kit.
I think you are right about a possible half shaft problem. Diffs should be physically the same, though.
I hate the way these rears are mounted in the cradle.
Large torque = recipe for disaster with the '04-'07 aluminum case mounted design. That's why steel is better for this design.
Just remember: larger gears puts, a new type of strain on the drivetrain,
as the wheels will not break loose as easily and the torque-stress will find a new location for deformation.
But, you already know that and probably do not beat your car.

04-01-11, 05:25 PM
I didn't know about the creative steel option for the rear. I just researched it and I like it. I know the rear ends are weak on our cars, and that to me seems like the best option for replacing it. at $600 for the brackets I would think it's not too bad, a good posi diff can be found for $200, what's unclear to me is the price of the half shafts and driveshaft adapter, both would have to be custom made. All this is going to add up to probably at least $1500. I can get an SRX diff for $300. I would be willing to spend the $300 knowing it may eventually break and upgrade to the creative steel kit at that time if I knew it was jut a bolt in solution. If it isn't, I think the creative steel brackets are the best solution out there so far (for the money)

04-02-11, 11:00 PM
I did swap the diff for a 2007 SRX with 3.23 and posi. I love it so far, all you have to do is to take the flange from the cts-v in order to bolt the driveshaft. I had to remove a thin sheetmetal cover over the pinion seal because it was rubbing on my cts-v flange. All the rest is the same. Now I can use all my gears. I don't race with my car, I use it mostly for highways. I will need to calibrate the speedometer next week

04-03-11, 10:10 AM
I'm interested in seeing about an mpg improvement. I JUST sold mine about 2 weeks ago and am already kicking myself. I'm most interested in hwy mpg.

04-03-11, 08:37 PM
sweet. I'm definately gonna do this and save the 3.73 in case I break the SRX one. Sounds easy. What kind of fuel economy are you getting? (hand calculated since the computer will probably show worse fuel economy since it still thinks you have 3.73 gears)