According to "Randy's Ring and Pinion" (what a name ) here's a list of all the cars that are equiped with the IRS 8.8 28 spline diff:

Cougar: 1989 - 1997
Mustang: 2006 - 2011 EDIT:99-04 cobra is only ones im sure and only 03-04 were 31spline at diff
Thunderbird: 1989 - 1997

And new link:
http://www.ringpinion.com/b2c/Produc...rce=DiffWizard


(Thanks to below)

 

Mustang is wrong 99-04 cobra is only ones im sure and only 03-04 were 31spline at diff

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I bought the Lincoln Mark VIII case and its perfect.

 

just a heads up to anyone buying or installing a 8.8 kit, the only ring and pinion you should get is one by ford racing, my richmond gear is very noisy, to the point i thought something was wrong, but nope they are just loud, a few mustang guys said they run nothing but ford racing stuff bc of this

 

has anyone had any clearance issues with their exhaust?
I have the Amuse R1000, and was just curious if I would have any problems before I order the Kit

 

I have the Richmond 3.9 gear in mine and it makes no noise at all. You sure your contact patern and backlash are good?

 

really? mine whines pretty loud above 100 mph, mustang guy said this was normal with a lot of the after market ring and pinions, either u got lucky, or mines messed up

 

the richmonds are known to be loud same with gm 10 bolt. thats why i went with a motive in my old trans am. but yes the ford racing gears are very good!

 

This is why I have yet to buy gears for my rear end. I only hear great things about Ford Racing gears and too many people complaining about the Richmond gears. Matt you may be the lucky one because there are way too many people complaining about the gears and I highly doubt there are THAT many bad installs. Many have stated that the whine is because of the material and the way the gears are cut. Not sure how much truth there is to that but I've read it on many of the Mustang, Chevelle forums etc.

I have been on the fence between the Ford Racing 3.73 and Richmond or Motive 3.90's. I can't see the 3.73's being that much of a slug on the streets compared to the 3.90. The mustang guys always say its hardly noticeable but that might be because of their tranny gearing.

If you guys are looking to run the 3.90's, I recommend going with the Motive 3.90's. Motive makes Ford Racing Gears so it "should" be of the same quality.

 

^I'm not the lucky one, mines loud as shit above 100mph, this may have been due to my aluminum drive shaft not being balanced perfectly also, I remember fbm saying it was difficult to balance them, now I have the steel one, I only drove the car for like 2 weeks with the supra trans and different steel driveshaft, but the cars so loud from everywhere now, motor, downpipe, turbo, trans(so loud), and the diff. it was difficult to pick out just the sound of the diff when ripping and everything is scraming, but on decel I could still hear something back there