DIY: Ford 8.8" Differential Swap
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Lexus Test Driver
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From: Wisconsin
DIY: Ford 8.8" Differential Swap
Mission Statement: This is a alternative from the $6,800 Boost Logic Ford 9" IRS swap, also a Alternative from the $2000 Supra 6 Speed Rear End with LSD . The 8.8's are known to be weak(500hp) stock, but when properly built they can handle 1000hp maybe more. I have not fully thought this swap out yet ether so if there are any points to be made please state. As for price I will be labeling with Things Required when I find out.
Things Required for complete rebuild 1000hp:
$250 - Mark VIII IRS Aluminum, Cobra IRS Aluminum, or Thunderbird IRS Cast Iron Differential
$190 - Stronger Differential Cover
$85 - Full Tilt Boogie Racing Solid Differential Bushings
$___ - Differential Adapter
$470 - Eaton Detroit True-Trac 31 Spline Limited Slip Differential
$___ - Custom 31 Spline Axels
$160 - Gears of Choice
More to come while I compile data and proceed with swap.
Benefits:
Huge Variety of Gear Ratios
Cheap Parts
Lightweight Aluminum Housing
Things Required for complete rebuild 1000hp:
$250 - Mark VIII IRS Aluminum, Cobra IRS Aluminum, or Thunderbird IRS Cast Iron Differential
$190 - Stronger Differential Cover
$85 - Full Tilt Boogie Racing Solid Differential Bushings
$___ - Differential Adapter
$470 - Eaton Detroit True-Trac 31 Spline Limited Slip Differential
$___ - Custom 31 Spline Axels
$160 - Gears of Choice
More to come while I compile data and proceed with swap.
Benefits:
Huge Variety of Gear Ratios
Cheap Parts
Lightweight Aluminum Housing
Last edited by 1siksc; Jan 3, 2012 at 09:45 PM.
well if i remember correct there is a difference between the 03 cobra irs and those other 2.
and as far as i know the 03 cobra irs is the only one worth a damn but even then its prone for mad wheel hop at the horsepower levels your aiming at. The bushing kit you list supposedly helps all that though.
also the cobra irs is gonna cost you ALOT more than 250 thats for sure.
and as far as i know the 03 cobra irs is the only one worth a damn but even then its prone for mad wheel hop at the horsepower levels your aiming at. The bushing kit you list supposedly helps all that though.
also the cobra irs is gonna cost you ALOT more than 250 thats for sure.
Thread Starter
Lexus Test Driver
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From: Wisconsin
I'm glad to hear others like the idea. The difference between the Cobra IRS and Mark Viii is the Mark Viii has only 28 splines internal diff while the cobra is 31 splines. Though this gets replaced with the new Eaton Detroit True-Trac 31 Spline Limited Slip Differential. Other then that the sub frame of them are different but that won't be getting used. Then for the tbird differential it will have the 28 splines and a cast iron housing. As for cost, there are some cobra owners getting rid of their differentials cheap since alot of them switch over to solid axels. I was hoping to do a solid axel earlier but a whole subframe would be needed to be made.
are you doing this to be different and or to save funds? So far you are in the money for $1,200 bucks not taking into consideration the other parts that aren't priced on your post...
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Interesting. Mustang parts are super cheap and very common. I have an 01 Cobra IRS at my disposal so I hope you finish this up.
The gearing choices are endless and you have sooo many different helical and clutch based diffs to work with.
4.56 with a detroit locker for the drag guys. 3.73 with trutrac for the road cars. Possibilities are endless.
The gearing choices are endless and you have sooo many different helical and clutch based diffs to work with.
4.56 with a detroit locker for the drag guys. 3.73 with trutrac for the road cars. Possibilities are endless.
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Thread Starter
Lexus Test Driver
iTrader: (8)
Joined: Aug 2007
Posts: 1,354
Likes: 2
From: Wisconsin
Be different and see if any change to save, to note this is making it a brand new differential and with buying the $2000 dollar 6 speed you would still need to get the axels and maybe rebuild.
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Joined: Apr 2008
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From: Canada
It's unlikely you'll be able to save any money if you want to do a good and especially clean job as compared to a mk4 rear end. Even if you do save a few bucks, nothing bolts in, you'll have to re engineer the *** end of the car to make it any sort of decent. If you want the challenge, go ahead. Granted I don't know what you've done with your car, starting from scratch just seems like a lot of work for minimal gain and maximum headache. Just my two cents.
I disagree with "minimal gain, and maximum headache."
Sure, it'll be a huge challenge to start with, but as said before, the domestic guys get alot of goodies, vs the mkiv guys, who get some cool-jdm-tyte-****-yo.
there's less than a dozen gearing options for the mkiv/sc differential, vs the 8.8 having almost unlimited options.
the 8.8" is probably the 3rd most common diff in existence (only to the 9", and 10-bolt), versus ours only coming in a limited number of lexus/toyotas.
If you break one of our rear ends, unless you live in Cali, you will pay hell to find a replacement locally. You will be hard pressed to NOT find one of these 8.8"s in a local junk yard (at least, here in the States).
Sure, the chances of breaking a differential are slim, but IF it happens, you're up **** creek without a paddle.
and looking at different examples of the 8.8 irs, I don't think it'll be nearly as hard to mount up as one might think (difficulty will be with axles...)
Sure, it'll be a huge challenge to start with, but as said before, the domestic guys get alot of goodies, vs the mkiv guys, who get some cool-jdm-tyte-****-yo.
there's less than a dozen gearing options for the mkiv/sc differential, vs the 8.8 having almost unlimited options.
the 8.8" is probably the 3rd most common diff in existence (only to the 9", and 10-bolt), versus ours only coming in a limited number of lexus/toyotas.
If you break one of our rear ends, unless you live in Cali, you will pay hell to find a replacement locally. You will be hard pressed to NOT find one of these 8.8"s in a local junk yard (at least, here in the States).
Sure, the chances of breaking a differential are slim, but IF it happens, you're up **** creek without a paddle.
and looking at different examples of the 8.8 irs, I don't think it'll be nearly as hard to mount up as one might think (difficulty will be with axles...)
I think the idea is good and very innovative, but you are comparing it to an entire 6 speed rear end which is why it seems economical, but you should factor in that most of us just drop lsd's into the existing Differential.
Its already in your SC, can handle lots of power, and there are plenty of ring gear choices that will bolt right up from various I6's and v8's with varying transmissions. you can also get solid diff mounts for it. The lsd costs more, but you could probably buy a few of them for the cost of fabricating a new rear end setup.
here are all the ratios that will swap over to your stock case.
97-00 SC400 3.266
92-97 SC300
6 cyl, AT (4.27 ratio)
6 cyl, MT (4.08 ratio)
98-00 SC300
6 cyl, AT (4.27 ratio)
92-96 SC400
8 cyl (3.92 ratio)
92-96 MKIV Supra
w/o turbo; (4.27 ratio) Limited Slip
w/o turbo; (4.27 ratio)
w/turbo, AT (3.769 ratio) Limited Slip
97-98 MKIV Supra
w/o turbo; (4.08 ratio) Limited Slip
w/o turbo; (4.08 ratio)
w/turbo, AT (3.769 ratio)
w/turbo, AT (3.769 ratio) Limited Slip
Its already in your SC, can handle lots of power, and there are plenty of ring gear choices that will bolt right up from various I6's and v8's with varying transmissions. you can also get solid diff mounts for it. The lsd costs more, but you could probably buy a few of them for the cost of fabricating a new rear end setup.
here are all the ratios that will swap over to your stock case.
97-00 SC400 3.266
92-97 SC300
6 cyl, AT (4.27 ratio)
6 cyl, MT (4.08 ratio)
98-00 SC300
6 cyl, AT (4.27 ratio)
92-96 SC400
8 cyl (3.92 ratio)
92-96 MKIV Supra
w/o turbo; (4.27 ratio) Limited Slip
w/o turbo; (4.27 ratio)
w/turbo, AT (3.769 ratio) Limited Slip
97-98 MKIV Supra
w/o turbo; (4.08 ratio) Limited Slip
w/o turbo; (4.08 ratio)
w/turbo, AT (3.769 ratio)
w/turbo, AT (3.769 ratio) Limited Slip
