Cadillac Owners Forum banner
26K views 93 replies 40 participants last post by  Brackets 
#1 · (Edited)
Gentlemen (and heavymetals),

Wanted to wait till most of the pieces were together before posting anything.

I, for the last 15 years, have been a die hard Ford guy. Owned 20+ Mustangs from a 1965 K code fastback to a 2003 Cobra with ~750HP currently. I always stayed active in my car community and knew the need our cars had for a differential solution since I started drooling over the V almost 4 years ago (just couldn't convince myself to plunk down 58k on a car).

As of this morning. the last of the needed peices are headed this way to start this process which should begin late March. My local Mustang/performance shop who I've used for 10+ years is going to be setting this up and running the actual selling of the product. I am just facilitating getting it started.

The plan at this point is to use the 8.8 IRS pumpkin found in several Ford Vehicles in place of the stock Getrag unit.

99-04 Mustang Cobra (aluminum)
89-95 Tbird/Cougar (iron)
92-98 Mark VIII (iron/aluminum depending on year)

I have a complete IRS assembly from a 2003 Cobra, spindle to spindle. Thanks for a fellow board member, I have a complete spindle to spindle 2005 CTS-V IRS as well( along with a second spare cradle). I have already taken my V down to the shop, removed the cradle and had Bill (shop owner/fabricator) take all the needed measurements to get the process started.

I know alot of people have taken this on with very little real world results/success. I hope to change this in short order.

The goal is to provide a solution centered around a modified IRS cradle to fit the 8.8 pumpkin into our vehicles. With two spare cradles, Bill will offer an exchange program ( with core charge) for quick turnaround times to keep vehicle down time to a minimum. Bill will be offering several packages for however complete the purchaser wants, all the way up to 100% complete/assembled, with pumpkin and modified half shafts.

My thoughts are if my Cobra can punish the stock 8.8 pumpkin with repeated 3K clutch drops with 650 ft/lbs of torque and drag radials, it should be plenty stout for 95+% of the CTS-V's rolling out there.

Goal price is under 3K complete, with lesser packages priced accordingly.

What I'd like in this thread are thoughts, suggestions, etc so we can make this as solid a solution as possible. I am fairly new to the CTS-V world, but NOT to the gearhead side of things. I'd love information/etc to help Bill make this a great package that offers a great alternate solution outside of feeding our cars stock diffs like Pez candy.

As we get closer to completion (shooting for 60 days), I will start a waiting list. I will be testing the solution in my car ( Bolt on 2005) before proceeding with any sales.

Thanks in advance.
 
See less See more
#6 ·
Good hunting, and good luck.

I personally prefer the Harrop diff.
I am with you that the Harrop diff is a great solution HOWEVER it's a bit cost prohibitve for most of us. Now for people like you that wipe with 20 dollar bills..... :p

Agreed that having multiple packages will serve everyone best. Will have to see where everything pans out.
 
#4 ·
IMHO, if you could sell a weld in or bolt in kit that came in stages they would sell like wild fire.
For example, Im an ok welder but not the greatest at fabrication. I would love a kit that is just the mounting brackets and axle shafts. Something that I can just measure, tack, fit the diff, and finish weld it. I can easily source my own pumpkin and find a drive shaft shop to modify the stock DS.
Someone else might want a complete kit with brackets, pumpkin, axles and drive shaft, then they could take it to any shop and have it installed.

With the V1's getting older and coming out of warranty, I think you are starting this project at the perfect time.

Good luck!
 
#5 ·
Good luck with it! I'm subscribing.


:food-snacking:
 
#7 ·
Don't forget about the wheel-hop. Guess you can address that with the axles.
Good luck
 
#9 ·
I will be happy if any solution comes to be.

Madman is to far and expensive

I like the one off copy idea of nutz but that seems to have died...
 
#10 ·
Being a Cobra owner I assume you are aware that a common complaint is that pieces of the IRS in that car will often break even under stock torque loads right?

Not trying to be a dick, but seems to me that you're considering a considerably cost inefficient swap with a known flawed solution.

There was a reason so many Cobra owners were willingly swapping the IRS to track loving GT owners for free.
 
#11 ·
I was just reading through this thinking the same thing. I had everything priced back when I had my Cobra. I was on borrowed time launching a stock IRS @ 6200.

Then we had a son and I had to get a "family" car.:suspect:

I love the effort, just not sure it is going to yield the best results.
 
#13 ·
Suggestions:

Sell the center section and corresponding CVs separately, some of us have already bought the larger diameter axles, others will never develop enough power to justify larger diameter axles, but want to stop worrying the rear will grenade at the next stoplight.

I would also consider selling gear combinations as well, some people want more than 3:73s, some less. I personally would love a set of 4.10s
 
G
#15 ·
Whata re you doing as far as gearing, also whats the weight differnce between the Getrag and 8.8? I know when fbodies step up to the heavier 12 bolt, it adds a decent amount of weight so they counter it by stepping the gears up a notch. Do you have any plans on that? I think the 3.73 gears in the factory unit make the car what it is and without the perfect gearing, the 4000 pound sedan will suffer dramatically.
 
#18 ·
Gearing will be up to the purchaser as far as choice. 8.8 has a WIDE range to select from so no worries there.

I will weight the diffs but don't have an iron 8.8 to compare. I couldn't see it being more than 20#'s, nothing that you would have to "gear down" to compensate for. The reason the Fbodies step up to a steper gear when going from the 10 bolt to a 12 bolt is that is takes more power to drive that axle setup. 8.8 IRS to Getrag IRS pumpkin should be comparable.

Once everything is sorted, Bill and I will hammer out specific packages to offer, covering as many bases as we can.

SHIPPING UPDATE : final pallet of parts should arrive Friday.
 
#17 ·
I have a Iron 8.8 and cradle sitting in the garage. Hope everything works out.
 
#22 · (Edited)
Not sure at this point on the HS's. I actually had envisioned using y'all, DSS (have a good in with them) or GForce to fab up a stock CTSV half shaft with the corresponding inner shaft for the 8.8. All details that will be getting sorted out. Same goes with the DS. I have a spare Ford yolk and a spare CTSV driveshaft. Leaving the engineering to Bill as the subject expert.

Thanks for backing the 8.8 in high HP applications. :cool2:

Was just in my Cobra Saturday further proving it as well. HA.
 
G
#39 ·
what would this allow the V to do logically? could we expect sub 2.0 60's on drag radials?

would it be able to handle slicks if thats what we wanted. I know there are variables i just wanna know what to expect with that chunk of change.

i would love to do it but even 4500 is a bit high for my wallet, not asking you to do work for free or even lower the price......thats just my personal opinion.
 
#33 ·
What he said.
 
#34 ·
Te be honest, I would if I could afford it. Most likely what will happen is me building my own setup. I have a pretty good idea that if it will work as planned, will be be very stout. Only problem with mine is it won't be a bolt in. Welding and cutting required. It would be nice to have something that would bolt in and not have to drag the torch and mig out.
 
#35 ·
Bill (fabricator) had made some GREAT progress and I should be able to post up some pics fairly soon. Both his business and mine EXPLODED shortly after we started this adventure so this kept getting put on the back burner in the name of necessity.

To confirm, this should be a 100% bolt in unit.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top