I have a 68 FB that I am redoing. I am stroking my 351w to a 408 and would like a posi rear to help keep more of that power on the road. Can anyone recommend a rear that will fit, have better brakes to help out with the @ 430hp that I am going for and hopefully can be found in the junk yard. Is there a rear from a 90s Mustang that will work?

 

Ford 9" standard axle for a '68 Mustang with a well built positrac 31 spline big bearing setup. Ebay is your friend. Also this:

http://www.mustangmonthly.com/techarticles/mump_0905_ford_9_inch_rear_axle/viewall.html

The axle is *all* about the punkin', bearings, and shafts. The axle housing is the same, so just get and use a standard 68 9" Mustang axle housing and rebuild the stuff inside it.

For better traction and wheel hop issues, subframe connectors, ladder bars, panhard bar, decent sway bar, all that "keep the axle from playin' around" stuff, and widest, decent to awesome griping tires you can fit, perhaps wheels to match that better. Don't want wide tires on skinny wheels, that looks nasty.

As far as better brakes, that's for for the front. Put standard ones in the back, they'll be fine. There are, however, brand new bolt on disc brake kits for the back if you desire, and that is what you should do if you want them.

BUT, the weight balance and transfer of that car will mean that unless you're running 50 miles per hour backwards, the backs are going to lock up easier with 'better brakes', and much like a motorcycle, the fronts are the ones you really want to have working good. Standard drums in the back would be more than sufficient for everything except tracking. I would put more in the front brakes, making them discs, as well as putting a power booster on the car, and putting the best shoes in the back I could get.

But that's me. I'm sure I'm gonna be blasted with "he's wrong, this is what you do, man." And that's fine, there's always more than one way to build things.

 

Since my car was a 289 I do not believe it has a factory 9 inch. Please Tell me I'm wrong. That being said I need to go get one. My thought was to hit a salvage yard to find a wrecked car that way I get a 9 in and posi in one that is done for $400. I would assume I could accomplish this with a 5.0 from the 90s. Not sure what years to look for and how the fit would be. Any thoughts here?

 

Actually... You might want to look into the 8.8" rear. 9" is costly, but apparently 8.8" is cheaper and still strong enough for the job. And when I said 'standard 9"', I meant if the car was originally equipped with it, or acquiring one meant for the car, not that it's in all '68 Mustangs. Sorry about that.

However, in looking around at the 8.8" swap idea you'll find that either the axle tubes would need work in the case of an Explorer, as it's carrier is offset, or in the case of a Fox you'll have to have the Fox brackets removed and proper ones welded on the housing. And/or shortening the tubes might be in order. It's not a bolt on in any case. An 8.8" means fab work, but cheaper internals. A 9" means bolt on, but it'll cost you to get there.

There's a whole world of googling to do on this. You need to do your research on it and then make a plan. If you can weld and can get the pinion angle figured out, then the 8.8 might be the way to go.

 

If your car was originally a 289 than it will have a 8" in it now. The foxbody Stangs from the 90s have the 8.8 rear. In order to do a 9", your going to be putting down a lot of money. If your not planning on producing crazy horsepower or dragging it, I would build the 8" or do the 8.8 which will cost a little more. Any of these options should give you what your looking for. Also, I would defiantly add the front disk and subframe connectors that were mentioned in the previous post.

 

So if I went for the 8.8 how much HP would it be able to handle. The guys at JEGS say the 8 was not designed for 400 plus. They have convinced me on the 9 in total set up with brakes at 2800. Please tell me that I can make this reliable for cheaper.

 

I saved the 8.8/posi/disk rearend out of my markVII, havent even measured it, but *heard* width was good on those- but pulled the axle out of the 69 a few days ago, surprised it had a 3.50 9 inch(open though), undecided now which one to use... plan is a mild 429, think the 8.8 would be ok as long as tires are moderate width- pretty sure drag radials or such would bust a 8.8 behind even a mild bigblock...

if looking for a cheap posi 8.8, the two local pull-a-part yards had 5 mark VIIs aailable last summer... mustang gts are a lot more scarce, but theyre pretty much the same underneath.

 

So I found a guy on Craig's list who parted out mustangs and picked up a 9 inch out of a 69 for $350. I called jegs and got new 31 spline for $99 each and posi auburn gear for $450. $250 at the resto shop to set it up and I am good. That should take any amount of Hp that you can put on the street. The research I did said an 8.8 was almost as good and with upgraded would easily handle 450 street Hp

 

Make sure to make some money off of selling that 8". They go for $200 or so around here.