Which 8.8" differential is on my SPF?

SunDude · #1 (**permalink**) 08-06-2009, 09:05 AM

I know from reading the Superformance MkIII owners manual 2nd ed. that the car uses an 8.8-inch Ford limited-slip differential (Traction-Lok?). But does anyone know exactly which 8.8" diff is being used? What is the part no. of the unit used by SPF?

http://www.fordracingparts.com/parts...20differential

I have chassis no. 1336.

Thanks.

RedBarchetta · #2 (**permalink**) 08-06-2009, 09:10 AM

You most likely have the same 8.8 that was also used on the Ford Thunderbird Super Coupes. At least mine does and your sequence number and build year is not that far off.

-Dean #747 (March 2000)

SunDude · #3 (**permalink**) 08-06-2009, 01:40 PM

Yep, Superformance LLC has confirmed that my car is equipped with an 8.8-inch diff from a 1990 Ford Thunderbird SC (Supercoupe).

Does anyone know if this was a 28 or 31 spline unit?

RedBarchetta · #4 (**permalink**) 08-06-2009, 05:49 PM

SunDude, they are 28's.

The Driveshaft Shop http://www.driveshaftshop.com/ sells 31 spline half shafts, but be careful because I've heard a few situations where the replacements were not EXACTLY what was needed. Some SPF owners have combined the 31's with a Detroit Tru-Trac (sp?) posi member and this combination is about as bullet-proof as you can make the 8.8.

Also add a Steeda brace to the rear cover (see my gallery for pics). Gear deflection under HARD acceleration has been known to crack the rear cover in extreme instances. I added the brace for insurance.

-Dean

Great Asp · #5 (**permalink**) 08-06-2009, 06:44 PM

The brace is VERY worthwhile

E

bobcowan · #6 (**permalink**) 08-06-2009, 07:45 PM

I don't own a Superformance, so I could be wrong. But, doesn't the front mount use rubber bushings? If so, that causes flex in the front. But the rear is solidly mounted. One end flexes, and one end doesn't; that's a bad thing with big power.

RedBarchetta · #7 (**permalink**) 08-06-2009, 09:41 PM

Quote:

Originally Posted by bobcowan

I don't own a Superformance, so I could be wrong. But, doesn't the front mount use rubber bushings? If so, that causes flex in the front. But the rear is solidly mounted. One end flexes, and one end doesn't; that's a bad thing with big power.

The rear mount that attaches to the cover is actually hinged to the rear cross-member. There is a little give there, but it's a pretty beefy hinge (for lack of a better term). Some that have gone to more rigid aluminum spacers in the front have actually ADDED to the problem (i.e. snapping off the ears).

-Dean