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Using a ford 9" for IRS
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Author:  RebecaLynn [ May 4, 2012, 9:31 am ]
Post subject:  Using a ford 9" for IRS

I have found several options for prebuilt ford 9" rear housing for IRS or I may be able to just take a steel center section and build my own. I have worked with the 9" alot over the years as I come from a family of oval track racers. I know they are strong would this be a good option as a starting place for a custom set-up.

Another option I may have is to use a Winter quick change center section and build it from there also, which would give more options in gears and also give it a more classic look in the rear.

Author:  Driven5 [ May 4, 2012, 11:43 am ]
Post subject:  Re: Using a ford 9" for IRS

Not that I should be one to talk, since I've got an (aluminum) 8.8 IRS sitting in my garage that will be lucky if it ever sees the north side of 200hp, but a nine inch is probably a bit of overkill for even a high powered build. Namely these differentials seem like they would add substantial cost, and obviously some bling factor especially for the QC center section, but I'm not seeing the extra strength making much difference in our cars. Lighter cars just don't need as big of diffs to handle the same power. While I'm sure somebody has done it, because there is always somebody who can break anything, I haven't even heard of any the V8 Miata that are running the 'weak' 7.5 IRS having trouble breaking them in their 2500lb cars. This includes includes both supercharged SBF, and I think even some LSx powered cars, some of which also see a fair bit of track time. It seems to me that a 31 spline 8.8 IRS with some aftermarket axles should provide more enough strength for just about any power level that you can put to the ground in a sub-2000lb car setup for street and road course duty. Then again, if you plan to change out gears for track vs street use, then the QC rear end would certainly have an advantage over a traditional 8.8 or 9 inch unit.

Author:  geek49203 [ May 4, 2012, 12:09 pm ]
Post subject:  Re: Using a ford 9" for IRS

**Disclaimer -- I'm still researching this stuff, others here might be Ford IRS experts....**

If you're looking for Ford stuff, there might be some cheaper / lighter alternatives that would handle about any HP you throw at it (I hedge on that last point after seeing that SBC 1000 hp "locost" on eBay yesterday).

I'm planning to use a first-gen (2000-2002) Lincoln LS rear assembly in my locost -- at least that is my intention as I make plans to go pick it up. I'm paying like $200 for the entire rear end assembly -- diff, frame bits, control arms, brakes, the entire rear assembly, etc. This unit is an 8" Ford I believe -- making it the unloved step child that makes it "locost". The rear track numbers lead me to believe it would work for a +4 build -- will know more when I measure things. From the factory it was designed for 260 hp. This rear end was used in Jaguar S-types as I recall and the 2002-2005 T-bird. Chances are it's gonna be a 3.58 rear, although it might be a 3.31, which would be close to the engine donor's 3.23. There are some with an aluminum rear diff covers -- I hope to get lucky. Ring Gear Diameter: 8.000, Spline Count: 28

Here is one comment from a Jag forum: "Gen 1 housing will fit a Ford 8.8 trac lok and with 8" stock gears." I hope that is correct. If that isn't true, eventually I'd go to my second pick, which is an 8.8" rear end from the second-gen (2003 - 2006) LS rear end. Most are 3.58. This was designed for 280 hp in the Lincoln. There is also a Lincoln Mark VIII IRS too, which I hear is aluminum. Seems to be oodles of parts and support for this one. I see that it gets used for various IRS conversions.

This doesn't mention earlier Ford Thunderbird SC IRS systems....

At any rate, if you want IRS, and want a Ford, there are alternatives. Given that these are designed for 4000 pound (give or take) vehicles with HP of 280 (give or take), it should be good out of the box for most of what we'd throw at it. Unless of course you've got a 1000 hp motor, like in the eBay ad....

Author:  RebecaLynn [ May 4, 2012, 7:51 pm ]
Post subject:  Re: Using a ford 9" for IRS

yes the 8.8 rear housing would also work great.

The QC rearend would be nice and look great, but also does not fit into my idea for say.

I am looking at trying to use some more commonly availble but good race quality parts, so that way if something happens, things can be replaced easier or on the same day and get back out on track faster. Is the idea. I also feel if I over build a little bit then less chance of part failure due to stress and racing.

I have no plan on using the 9" case show in the pick because they want way to much for it. I am looking at using a strange steel center section with shortened or stub tubes and stub axles with CV joint ends attached is the idea. SO I can convert it over to the C6 corvette hub spline pattern

Author:  oldejack [ May 4, 2012, 9:05 pm ]
Post subject:  Re: Using a ford 9" for IRS

Well I like the idea of a fab'd up 9 inch housing. Out of curiosity though, have you considered the Dana 44?
Slightly smaller and lighter, just as readily available aftermarket support, actually appeared in the Jag as an IRS unit. ..
And if it'll hold up to 350 HP / 33" tires on my 1/2 ton it should be more than strong enough for a LoCost.


edit>>> minor brain stutter.... The Dana 44 is used in Vipers too, along with a lot of Corvettes.

Author:  RebecaLynn [ May 4, 2012, 9:58 pm ]
Post subject:  Re: Using a ford 9" for IRS

no I have not thought about the Dana44.

Is it a drop out center section like the 9". I will look it up. I figured with a drop out style center section, it will make changing gears easier. This is what we used in late models, and IMCA modifieds for years. Been around more circle track racing in my life.

Author:  oldejack [ May 4, 2012, 11:02 pm ]
Post subject:  Re: Using a ford 9" for IRS

Naw, no such luck, the chunk goes in from the back and the pinion from the inside with the shaft going out the front. ..
Not bad if you stay in the same pinion range but not something I would want to do in a hurry.
You don't really NEED the case stretcher most of the time, a couple of pry bars is usually all that's needed but it does make tear down easier.
Now that I think about it, the C4's used them as well.

Author:  seattletom [ May 4, 2012, 11:16 pm ]
Post subject:  Re: Using a ford 9" for IRS

RebecaLynn,

You might consider the C4 IRS, available in Dana 36 and Dana 44. Info and pics available here:
viewtopic.php?f=4&t=13213&p=135591&hilit=corvette+c4+irs#p135591

For the front end, lots of info on different Corvette spindles available in this thread, including a Solstice spindle modified to use a Corvette hub:
http://ls1tech.com/forums/suspension-br ... dle-9.html

And below are pics of C5/6 front and rear spindles as used on the continuation Scarab. The IRS is built around a Winters QC center section and inboard brakes:

Author:  RebecaLynn [ May 6, 2012, 1:49 pm ]
Post subject:  Re: Using a ford 9" for IRS

I found a 9" IRS housing from Currie which I aam planning on using at lot better price than the one I showed up above. The QC style would be nice for a old school classic design.

I have winter QC in both of my 27' and 32' fords, they are nice, but not what I need for this project i think. I went away from that design style for the most part, but we will see where it goes.

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