Hey guys,
well I have the money in the bank, and am realizing that it would be smartest to build my differential, then get my rims for my car. (this is before I have the motor, or have began to build it etc...) The diff im thinking I want is a ford 9", and I am thinking about going with the one that grannysspeedshop has.

http://members.tripod.com/~grannys/newproducts.html (shown here about half way down..)

By the looks of it all the suspension remains the same, and it still utilizes the stock 4 link setup. But my questions are about the axles, and setting up the brakes and so forth off this diff. I figured the forged axles would be overkill (goal is 400-450 RWHP, rotary power of course...). But does anyone know if these axles are full floating, semi floating or partial floaters? I am curious as to what ill have to do as far as bearings go.

Does anyone know what brakes, calipers etc I can use after I get this diff? I am doing the TII big brake kit up front, and it would be nice to have all the same bolt pattern.

My next question is what differential cage do you guys think would be best for a street/auto-x cars? I know like a eaton locker is out of the question because of the problem of it locking up when one tire breaks loose around a question. So I was thinking maybe a torsen cage would be the best option?

I have tried to contact granny's for some more information, but have not heard back from them as of yet...

 

9" is very heavy, 8.8" will easily handle 450hp and weighs a lot less, IMHO.

 

And does anyone know if I need to supply my own diff carrier? There isn't one pictures... I guess I should try to get ahold of grannys again lol.

But is it possible to get a 8.8" that retains the stock suspension points? If so then I would deffinately look into it.

 

If you are going with a Ford 9", just get a stock-type "Traction Lock" diff. They are almost exactly the same as the LSD originally offered in the 1st gen. A clutch-type LSD. Handles plenty of power, easily rebuildable, and rather inexspensive.
For the rear brakes, either make an mounting plate for the T2 rears, or look for a rear disc conversion kit for the 9". There are tons of kits available for both the 9" and 8.8", since both are popular swaps into other cars.

 

99% of the time, you will need to supply your own 3rd member, or buy one at an additional charge.

 

V8 swap section would have experience at these mods, but why don't you upgrade your suspension mounts at the same time, why keep the flawed stock set up.

Its not hard to fabricate a 4 link, just do your homework.

 

One tip, do NOT spend the money for an Auburn diff. A freind of mine did that, and it became a very exspensive open diff in about a year and 1/2. These units are not rebuildable, and require an extensive "Break-in" period that must be followed, or you will trash it.

 

a ford 9" is WEAKER THAN A 8.8, due to the 9"'s removable pumpkin design.

the ONLY reason to go with a 9" is if you need to change differential gear ratios regularly. Your wasting your time with the 9"

 

http://www.matthewnanney.com/whitev8-80.htm

Pics of an on the cheep install.

 

just a heads up, from personal experience and from what ive heard from their customers, it is nearly impossible to get ahold of grannys through email, its best to call them.

 

But the 8.8 has those craptastic axle bearings that the rollers actually ride on the axle shaft.
Granted, they don't require a press to replace, but one bearing going bad can scrap the axle shaft right along with the bearing.
That 3rd pinion bearing on the 9" makes it very desirable with high HP launches, and it doesn't need all the trusses and braces the 8.8 does, to come close to the brute strength of a 9".
I wonder why a 9" is such a popular swap in the late model mustangs that were originally equiped with the 8.8..... I know why it's popular with the 7.5 crowd.

 

Hmmm it looks like there is alot of pro's and con's of both that I haven't really heard of. This is honestly the first time i've ever heard someone say that a diff with a removable carrier is infact weaker than one with a non-removable carrier.

And I don't really want to have to fabricate a new 4 link setup, just for the fact I don't have a welder and don't want to spend a ton more time on fabrication than what I have to.

 

Dan, you're working/learning to be a mechanic, right? Chalk this up to one of those learning experiences. You already know my thoughts on this, do right the first time and only do it it once.

Refabricating the 4-link set up now will save you in the long run, especially if you want a drag monster that launches well.

Head over to the Mustang forums and study up there on the 8.8 and 9" rear ends, they know much more about them than we do.

 

K thanks for the advice.

 

So the ford 8.8" diff isn't straddle mounted? That kinda sucks because a overhung design seems like it would have alot of deflection when tons of power is thrown at it.

I posted up on the mustang forums for some help with the differences between the 2 diffs, but they seem to be more interested in loud exhaust, and mullets.

Im going to keep researching and hopefully ill come up with a good setup that will be reliable, and able to handle the power!

Another big question I have is about gearing. I know it would be nice to go to a gear like a 4.444 to offset for the huge 17" rims in the back. But at the same time won't a shorter gear set like that not give a larger turbo time to spool up?

 

It all comes down to your net final drive ratio in each gear. 4.44 gears will put my speedo back to reading corectly, almost, instead of reading nearly 10% low with my 15's. You are correct on not wanting to go too short on gearing, you won't be in boost that long if you go to too short.