Hi Guys,
I'm redoing my 68 fastback totally (nut and bolt inside/out top/bottom). It's just about totally apart now ... not much left on it exept the wiring harnesses. Anyway, I was wondering if anybody has any experience changing over to the new 8.8 inch rear differential? This is the way I want to go as my 8 inch is not possi and won't stand up to the hp and well the 9 inch is just getting old anyway (not knocking 8 or 9 inchers they were great in their time and probably still are). I just want something with way less internal friction and drag and I have read that the 8.8 limited slip is the new 9 inch of the millenium. If anyone has any input on this I would really appreciate it and thanks before-hand.

 

Just getting ready to do that with my '66. I'm building a Fox platform 8.8 from scratch to get exactly what I want.

(IMO) You've got a lot of ways to go with an 8.8, but the easiest two are either a Fox body or an SN95. The difference is the axles, so an SN95 is going to be a little wider than your stock width. But it comes with 5 lug axles, and disc brakes. You can use a deeper backspace for your wheel to make up the difference.

The Fox 8.8 should be the same width as your stock rear end.
If you want to run rear disc with a Fox 8.8, it gets a little complicated. The Fox 8.8 is 4 lug, and has a shorter axle due to not having the ABS sensor gears. So you can't just put SN95 discs on. There are conversions available to swap in 5 lug axles and disc brakes. The best deal going is through North Race cars. This allows you to run the 11.65 Cobra rear discs. Great people!!! You are on your own for hooking up the P-brake though. If you aren't going to run a console it's not too dificult, just fab in the P brake handle assembly from a Fox body onto the trans tunnel. If you are a good fabricator, you can always fab in a foot operated brake (that is my plan).

The only spring perches I could find are for 3" tubes, and the 8.8 is just at 2-7/8" diameter, so you'll need some welding skills. Also I went to Cobra Automotive for U-bolts. What a mistake!!! last time I ever deal with them. I am hoping that Ranger U-bolts will work. Haven't had a chance to go get some yet. I picked up Caltracs and Maier racings adjustable Pan Hard bar, and both come with spring plates, so that part is easy.

Here are some of the things you want to look out for:

1). Get the rear from a GT only. the V6 is 7.5" rear. All GTs came with a clutch style limited slip carrier which is a bonus.
2). Make sure no one has messed with it at all.
3). Look closely for chips, or pitting in the ring gear.
4). Most 8.8's have tall gears (low numerical number). If you are planning to swap gears, I'd highly advise sticking with Ford Racing Products. It makes set up much easier.
5). get the brake fitting off the body of the GT. Ford does not make this fitting any more. If you get the fitting you can use a stock Mustang brake hose. This fitting is on a bracket attached to the body just above the pumpkin. In fact if you pull the rear from the car, it is the fitting at the body the hose is attached to.
6). If you want to stick with the drums (which work very well) FRPP has an axle/drum kit that is a direct replacement so that you will have 5 on 4.5. www.stangstore.com should have these at a good price. They are also good people to deal with.
7). If you are going to run a lot of Torque and want to run slicks, get a rear end girdle to help support the carrier bearing caps. This will really stabilize the gears.
8). Stock pinion angle is 3* I would suggest you have the axle housing in the car when you weld up the perches. This needs to be done right or you can end up having issues from axle seal leaks, to breaking axles depending on how far off you are. Or take it to a good shop and have them weld everything up for you.

There are other swaps available, but they take more work.

Good luck. Let us know what you decide.

 

You can get an Aerospace kit fro around $475 and 5 lug axle kits for about $250. I have a hookup for them if you want you can PM me.