CREATIVE STEEL: CTS-V 8.8 Rear Diff Swap BOLT IN
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2004-2007 Cadillac CTS-V Performance Mods Discussion, CREATIVE STEEL: CTS-V 8.8 Rear Diff Swap BOLT IN in Cadillac CTS-V Series Forum - 2004 - 2007; As some of you know, we've been working on a solution for the "less than ideal" Getrag rear differentials that ...
  1. #1
    MotorMounts's Avatar
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    CREATIVE STEEL: CTS-V 8.8 Rear Diff Swap BOLT IN

    As some of you know, we've been working on a solution for the "less than ideal" Getrag rear differentials that our cars came with.
    There has been a lot of talk over the years about the "Diff Swap" topic and there have even been a few shops that have succeeded in pulling it off. After reading some of these success stories, like many of you, I was put off by what was required to have this work done.
    First was the price.... $7500...Whoa! Questions: "How easy does your money have to come" and "How bad do you need the swap" before $7500 becomes the best choice.
    Second was the shipping of the car. I know I don't want to put MY car on a transport truck to have it shipped to... Faraway, USA. This adds more money to the swap and invites damage to the car that no one knows how it got there. "Wasn't me". On top of that, you don't have the car to drive for who knows how long (while it's in Faraway.)

    Objective: Identify an OEM production IRS differential that was stronger than the OEM Getrag, build the brackets that will allow the installation of said differential in an unmodified 04-07 CTS-V sub-frame.

    So....... we started looking around for a suitable "production" donor car to steal a rear end from. We quickly arrived at the Ford 8.8. They come in 89-97 T-Birds (Cast Iron) and 93-97? Lincoln Mark8 (Cast aluminum). They are strong, they are plentiful, they have unlimited gear ratios available, they are comparable in size to the Getrag and best of all... we had one in stock to play with (it was planned for another project that has been put on the back burner).
    This is what we came up with. A completely BOLT-IN 8.8 diff swap. We built brackets that bolt the 8.8 housing into the CTS sub-frame with no modifications to either one or any other part of the car. When I say "Bolt-in", I mean BOLT......IN. You can install this kit in your driveway with simple hand tools(air tools and a friend suggested) in less than 8 hours. The exhaust system will be the only part of the swap that will be a "as required". I have a 2-1/2" MagnaFlow system on my car, all I had to do was dimple in an area that was 2" X 2 1/2" X 1/2" deep to clear the diff housing.

    For you guys that track your cars, excessive heat build-up in the diff can be a problem, so we machine the rear cover of the diff and Tig welded on a boss that has two 3/8" pipe ports. These are provided so the customer may add a cooling system to the diff as required.

    I mentioned in another thread that the cost was going to be $3600, well..... after adding all the small "seemingly inconsequential" expenses such as bolts, gear lube, cleaning solvent, powder coat, blah blah blah. The price is going to be $4,225 plus shipping. I'm not even sure this is gonna get it. I could add a $1000 to the miscellaneous category to cover the unexpected but that would defeat the project, so until the bean counter tells me to up the price it'll be $4,225 plus shipping.

    What comes in the kit:

    Good used 8.8 housing, assembled with the following:
    New Motive Gear gears (Factory CTS-V 3.73 ratio) others available
    New Motive Gear bearings through out
    New Eaton TrueTrac Part #913A561 31 Spline
    New Chromoly axles with Porsche style 930 Inner CV joints 31 Spline
    Drive Shaft Adapter to mate the OEM CTS-V Drive Shaft to the 8.8
    2 Quarts Redline 75w-140w synthetic gear lube
    1 Tube Friction Modifier

    At this price you will need to re-use your outer OEM CV joints. I haven't read anything mentioning that these are a problem, so I saw a way to save some money on the kit. If the OEM Outer CV's become the next weakest link then we can address that issue on a "as needed" basis, or I can get a price for those who want an up-graded CV right from the start.
    At this point I need to know how many people are interested in what I've proposed and be willing to put down 50% ($2100), to get the ball rolling. I also have ideas to remove the expense of the drive shaft adapter in order to put that money towards a completely new (One Piece)drive shaft which is another up-grade these cars need anyway.
    I'm sure that I have forgotten plenty of information that you guys will have questions about. Put on your thinking cap, let's do some brain storming and get this differential issue solved.

    Here are a few pictures for your viewing pleasure, Max
    Attached Images
    Our phone number is 503-316-1811 We're here M-F, 8-5 Pacific Time.
    http://www.creative-steel.com
    maxx@creative-steel.com

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  3. #2
    heavymetals's Avatar
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    Re: CREATIVE STEEL: CTS-V 8.8 Rear Diff Swap BOLT IN

    Good going Max!

    I still have a cradle sitting for my swap job.

    I was looking at a Holden but whatever, nice going!

  4. #3
    tommy compton's Avatar
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    Re: CREATIVE STEEL: CTS-V 8.8 Rear Diff Swap BOLT IN

    Does our diff ever look like a puney turd compared to a real diff. I'm afraid my B&B exhaust would need more than a dimple.

  5. #4
    lunarx's Avatar
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    Re: CREATIVE STEEL: CTS-V 8.8 Rear Diff Swap BOLT IN








  6. #5
    lunarx's Avatar
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    Re: CREATIVE STEEL: CTS-V 8.8 Rear Diff Swap BOLT IN

    Looks good.
    Is there a demo car running?

    You make it sound simple.
    How come nobody ever did this before?
    What were some of the technical challenges that you overcame?

  7. #6
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    Re: CREATIVE STEEL: CTS-V 8.8 Rear Diff Swap BOLT IN

    I'm interested max but what's the feedback. I mean noise/clunk, weight, have you hammered it nicely.

    And B&B user here so my dimples may have to be gaping holes.

  8. #7
    lilgCTS-V is offline Cadillac Owners Enthusiast
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    Re: CREATIVE STEEL: CTS-V 8.8 Rear Diff Swap BOLT IN

    looks sick what would the price be if you get your own diff ?

  9. #8
    MotorMounts's Avatar
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    Re: CREATIVE STEEL: CTS-V 8.8 Rear Diff Swap BOLT IN

    Quote Originally Posted by lunarx View Post
    Looks good.
    Is there a demo car running?

    You make it sound simple.
    How come nobody ever did this before?
    What were some of the technical challenges that you overcame?
    Thank you for posting the pictures. Yes, there is a Demo car running...My car. The 8.8 has been in there for 3-4 weeks and about 300 miles of trouble free driving.
    The install is very simple and I have no idea why this hasn't been done before. By no means was this a quick R&D, but now that it's done the installs from now on a piece of cake.
    Technical Challenges...? Fine tuning the exact location that the diff had to be in to clear any obstacles. As the pictures show, the 8.8 is noticeably larger than the Getrag unit. The 8.8 uses every bit of extra space available, on the top, bottom, left and right. The other challenge was the drive shaft adapter. What I have now works great but it's my third version.

    The only problem I have is that the wheel hop is more than I was expecting/hoping for with the offset diameter axles. I have started to build new stiffer sub-frame bushings to see if they will help. The OEM bushings are just like the rest of the bushings in these cars... SOFT CITY. The sub-frame is allowed to "float" around on these spongy bushings which has to be a major contributor to the wheel hop problem these cars have.

    Thanks for the comments and questions, Max
    Our phone number is 503-316-1811 We're here M-F, 8-5 Pacific Time.
    http://www.creative-steel.com
    maxx@creative-steel.com

  10. #9
    Dan_Gurney is offline Cadillac Owners Fanatic
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    Re: CREATIVE STEEL: CTS-V 8.8 Rear Diff Swap BOLT IN

    Would you consider a kit without the differential for those junkyard dogs amongst us? I have a feeling a lot of the cost is in the new gears/diff where there are a lot of good used complete units out there that would satisfy many of us.

    I say this because it seems like the 9" conversion out there is a better deal... don't shoot me yet... I love to see an alternative out there like this (especially from somebody like you), this is really what most of us need, not a 9", but for $1250 more we get a stronger diff which is 100% new, a new 2-piece drive shaft, and complete race axles, (inner and outer CV's bulletproof) (although this does also require a little fabrication)

    To counter myself as well the inner cv's fail way before the outers so they may not be as required... but still weighs in on the mind.

    Oh and the most important part though... Great work in putting this together and offering it for sale. I won't turn down having options/competition

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    CI-V-IL is offline Cadillac Owners Fanatic
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    Re: CREATIVE STEEL: CTS-V 8.8 Rear Diff Swap BOLT IN

    Max, i'm with Dan_Gurney. Any possibility of buying a kit minus the differential? I have many of these in my area with 3.73 gears stock. I'm not opposed to buying one of them for 100 bucks and freshening it up then buying the rest of your kit. Would be looking for the diff brakets and any related nuts/bolts as well as the New Chromoly axles with Porsche style 930 Inner CV joints 31 Spline and Drive Shaft Adapter to mate the OEM CTS-V Drive Shaft to the 8.8.

    Thanks Max!

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    CancerJCC is offline Cadillac Owners Connoisseur
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    Re: CREATIVE STEEL: CTS-V 8.8 Rear Diff Swap BOLT IN

    Quote Originally Posted by tommy compton View Post
    Does our diff ever look like a puney turd compared to a real diff. I'm afraid my B&B exhaust would need more than a dimple.
    Quote Originally Posted by ichpen View Post
    And B&B user here so my dimples may have to be gaping holes.
    Yeah any pics with the exhaust "dimple" required? B&B users are going to have to get some re-routing done I would say.

    Quote Originally Posted by lilgCTS-V View Post
    looks sick what would the price be if you get your own diff ?
    I think this is the big one. I would be fine with putting a good used 8.8 in and dealing with failure as it comes up, if ever. This would put the price point in my range assuming I have no failure. (Replacing something that is still functioning is a lot more costly to me than if I had a failure and needed a new diff).

  13. #12
    CancerJCC is offline Cadillac Owners Connoisseur
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    Re: CREATIVE STEEL: CTS-V 8.8 Rear Diff Swap BOLT IN

    Oh and by the way I LOVE that you are making this a bolt in solution. Many of us have most common hand tools but lack a torch/welder to cut and box the rear-sub frame. This should fill the market void nicely especially if you offer it up as a "tuner kit". (minus diff)

  14. #13
    tommy compton's Avatar
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    Re: CREATIVE STEEL: CTS-V 8.8 Rear Diff Swap BOLT IN

    Quote Originally Posted by MotorMounts View Post

    The only problem I have is that the wheel hop is more than I was expecting/hoping for with the offset diameter axles.
    Would not want to deal with that again, any chance on killing the wheel hop with axle diameters alone ?

    Kit does sound like a good option, hell if I could find used ones, I'd just have a stock pile of them. Maybe even carry a spare in the trunk lol.

  15. #14
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    Re: CREATIVE STEEL: CTS-V 8.8 Rear Diff Swap BOLT IN

    Curious to know the price of the kit minus the diff also

  16. #15
    MotorMounts's Avatar
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    Re: CREATIVE STEEL: CTS-V 8.8 Rear Diff Swap BOLT IN

    Not ignoring the questions....crunching the numbers.
    Our phone number is 503-316-1811 We're here M-F, 8-5 Pacific Time.
    http://www.creative-steel.com
    maxx@creative-steel.com

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