Discuss 1971 Open to Posi rear end.... on AllFordMustangs.com, the place for Mustang enthusiasts.
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I found a junk yard that has all these ford 9" rear ends for $100 each. He has them tagged with the year and make of the car they came from. Does anyone know which year and model, if any, will be a direct replacement for a 1971 mustang. I'm thinking none, but thought I'd ask the experts
Is it wise to do a swap or should I just keep my stock open 9" with 28 spline and drum brakes. My goal is to upgrade the stang with disc brakes and posi rear, but if one that already has the disc brakes and posi can be had for $100, then that'll be a major savings in the budget.
How much does a disc brake conversion, detroit locker and gearing cost? I did a price check and it's well over $1000 and not to mention the cost of shipping these heavy parts to me in Hawaii.
Something to think about is going to the 8.8" Explorer late model that came with the disc brakes and usually a 3.73 or 4.10 rear end. Around here you can pick them up for about $250. You'd have to move the spring perches, modify brake lines and drive shaft. I'd have to check the width but seems real close.
The 9 inch is the strongest rear end made top fuel cars run them,Yeah all the parts are beefed up but the design is still the same.Yeah the 8.8 is what most fords mid 80s to today use.The 8.8 is ok but a 31 spline 9 inch will hold more power.
Keep the 9", they're stronger than the 8.8 and the 9" with the removable center section is much easier to work on. I don't advise using a 9" housing with the disc brake assy already attached as these are most likely Lincoln Versallis housings. The brake parts are getting very expensive because of the lack of demand in the aftermarket and availability of these parts are getting worse as time goes on. Plus the Versallis housing is too narrow for your car.
You can remove the whole center section with the limited slip and install it into your current housing. It should be a 28 spline unit if it's a Versallis. The Versallis gear ratio sucks, though. They are all usually in the 2.80:1 range. Another problem is the drive shaft yoke not matching.
You have the option of just transferring the limited slip portion into your current differential. Just transfer your present ring gear. This way you keep your gearing and drive shaft yoke and you will have limited slip. The only thing needed is to reset the gear mesh pattern.
If you're going to use this set up don't forget to check the clutches for wear and to use friction modifier in the gear lube.
Thanks for the replies! OKay, did some local searching online and in newspapers and found two more options. New Tractech detroit locker that'll work in my housing (28 spline / small bearing) for $250 or Complete 86 Bronco with a 9" 31 spline 3.55 posi rear end for $100. Can I take the whole center section and buy 31 spline axles for my housing? Do they even make 31 spline axles with small bearings?
They made quite a few small bearing 9" rears, and that's what's correct for a Mustang and most 'car' rears, not to mention that's what most of the rear disc kits require.
But, it seems like everything I've seen in the junkyards is in a later model full size car or a truck, and 99.9% of those used large bearings, so it's definately an oddball to find a small bearing rear lying around these days. I've found plenty if I look for one specifically for a mustang, but I've saw ONE in a junkyard and the guy was busy getting it ready for his 67 Coog.
Here's another odd choice, a 94-98 Mustang GT 8.8". They are posi, disc brake and exactly the right width for a 71-73 Mustang, just add spring mounts and torch off the sway bar and coil spring junk. Really cheap too, since the weird axles make the assembly too wide to fit other cars.
Your best bet though, since I see you said you already have a 9" is to do the SVO mustang or Crown Victoria disc swap and put in a posi 3rd member. Crown Vic swap is like $150 and I've got less than $325 in my SVO swap...the 3rd member, assembled and ready to bolt in is probably $600.
66 coupe 5.0/T5, home-brewed power 4 wheel disc setup, 350hp+, looks like it belongs in 1968
Keep the 9", they're stronger than the 8.8 and the 9" with the removable center section is much easier to work on.
I disagree with that, stock vs. stock the 31 spline 8.8 is every bit as strong as a 9". Granted there are many more aftermarket options for the 9". At work we have a company drag car (89 mustang, 450hp 302, b&m AOD with 3500 stall) and we're going on our 3rd race season on the stock 28 spline 8.8 with the stock traclock l/s and a set of moser 28 spline shafts without any problems.
I pull wrenches for a living and I'd rather work on an 8.8 than wrestle a 3rd member off a 9" anyday.