Steve Baur
Former Editor, Modified Mustangs & Fords
January 1, 2007

Step By Step

View Photo Gallery
Mmfp_0701_01z Ford_mustang_fox_body Rear_dropped_transmission
When five speeds aren't enough, it's time to step up to the T56.
Mmfp_0701_02z Ford_mustang_fox_body Transmission_housing
Currently, the Tremec T56 is used in the Dodge Viper, the Chevy Corvette Z06, and Aston Martin's DB7 Vantage and V12 Vanquish. Our particular application requires PN 1386-000-012, which provides you with a mechanical speedometer, a 10-spline input shaft and 31-spline output shaft, along with gear ratios of 2.97 First, 2.07 Second, 1.43 Third, 1.0 Fourth, 0.80 Fifth, and 0.62 Sixth. You can buy the transmission separately, but we recommend calling D&D Performance as it sells the transmission and all of the necessary swap parts for $2,699.
Mmfp_0701_03z Ford_mustang_fox_body Remove_midpipe
To begin the installation, we removed the mid-pipe and driveshaft.

When The EFI Mustangs of the late '80s blasted onto the scene, they benefited from a trick, new injection system that helped develop an abundance of torque. These 302s made great power, and many were backed by the T5 manual transmission-a four-speed with Overdrive that allowed the Mustang to run a relatively short First gear (3.35:1) and a short aftermarket rear gear (like 4.10s) while maintaining a comfortable cruise rpm thanks to a heavily overdriven Fifth gear. In 1993, GM's F-body twins ditched the five-speed for the T56 gearbox, a box that is more capable of handling even more torque. The T56 also increased fuel mileage due to its double Overdrive Fifth and Sixth gears.

Once the Mustang switched to modular power in 1996, its inherent lack of torque allowed the manufacturer to make mild upgrades to the five-speed unit until 2003, when the super-charged Cobra Mustang's 390 lb-ft of torque required something far more capable.

Today, the latest S197 chassis Mustangs still employ the five-speed in Tremec 3650 guise, but many Mustang owners have sought out the T56 gearbox, both for its extra power-handling capacity and its six-gear configuration.

Years ago, we installed a T56 in Project Superfly, and more recently, we dropped one into an S197 GT ("Love Plus One," Aug. '06). We haven't installed one in a Fox-body Mustang until now.

MM&FF's illegitimate project car, ProCharged Pony, has been fortified with numerous upgrades over the last four years, including a D.S.S. Racing 331ci, ProCharger-blown powerplant that has generated 580 rwhp and some 550 lb-ft of torque. Putting that generous amount of power to the ground is handled in part by the DTS 8.8 rear axle assembly, which has been muscled up with 33-spline axles, 9-inch axle ends, and an Eaton differential.

Step By Step

View Photo Gallery
Mmfp_0701_07z Ford_mustang_fox_body Remove_bellhousing
With the transmission out of the way, we started removing the right-side header so we could remove the bellhousing.
Mmfp_0701_08z Ford_mustang_fox_body Bellhousing
The clutch fork and pivot ball must be reused. We found the only way to get the fork and throwout bearing to fit on the input shaft of the T56 was to install the pivot ball and throwout bearing on the fork, and then screw in the pivot ball while it is still clipped in. Be sure to lather up the input shaft with grease prior to this.
Mmfp_0701_09z Ford_mustang_fox_body Block_plate
Since our car had the scattershield, we had to procure a stock manual trans block plate for use with the T56. These are easy to come by if you haven't kept your stock piece.

The weak link between these two items is the stock 147,000-mile T5 transmission. While it has survived several mid-11-second passes, it's showing its age with a healthy crunch when shifting into Third gear. The stock T5 has never received the full brunt of the supercharged 331 either, which may be why it has survived until this point.

That being said, we thought it wise to upgrade the box before it disintegrates into an unusable mess of metal, however, we weren't looking at a rebuild. Instead we opted for Transmission Technologies Corporation's T56 six-speed gearbox. TTC supplied us with the Tremec T56 unit, though consumers will have to go through one of its distributors, such as D&D Performance in Wixom, Michigan.

D&D has perfected the six-speed swap for all late-model Mustangs and offers all of TTC's Tremec transmissions in addition to numerous upgrades for each one. The Fox-body version of the T56 has been fitted for a mechanical speedometer (both F-body and newer Mustang pieces utilize an electronic speedo) and an integrated bellhousing that bolts right up to our Ford small-block.

The company can also provide a new crossmember and driveshaft for your application, as well as SFI bellhousings for racing. D&D's Don Walsh Sr. was extremely helpful in selecting the right parts for our installation.

The actual transmission swap was fairly simple, with only minor modifications needed to get the job done. The T56 weighs in around 122 pounds, while the T5 comes in at a scant 75. We scrubbed off a bit of the difference by exchanging our Lakewood scattershield for the integrated aluminum unit, and the extra torque capacity (400 versus 300) of the T56 was well worth it.

Step By Step

View Photo Gallery
Mmfp_0701_13z Ford_mustang_fox_body Crossmember_clearance
You'll want to check the clearance between the transmission and the crossmember as production tolerances can create interference that results in interior vibrations most notably through the floor. We had to grind the notch a tad more to remedy this.
Mmfp_0701_14z Ford_mustang_fox_body Header_collector
With the crossmember in, we reinstalled the header collector flanges and lengthened the reverse light harness to reach the other side of the transmission.

Astute readers will stop here wondering why we installed a stock T56 rated at 400 lb-ft versus a Tremec TKO or Viper-spec T56 that is designed for more aggressive engine combinations.

First, we've never installed a six-speed in a 5.0, and we just needed to get that under our belts. Second, six-speed transmissions are the future, and it just plain sounds cool to say you have one in your Fox-body Stang. And third, we like the smooth shifting of the stock T56 over the other options. After talking with Jim Averil, Tremec's marketing manager, we agreed to upgrade it in the spring with TTC's new TR-6060 six-speed unit, which is the same trans that allows the '07 Shelby GT500 to put its copious amount of torque to the pavement in a reliable manner. Be sure to check back with us for that one, as we'll be giving you the skinny on the new transmission, which is slated to eventually replace the T56 unit.

When you get into the TKO and other five-speed alternatives on the market, the price difference is not so great as to outweigh the benefits of the six-speed. While it's not on the cheap list, buying one transmission that will hold up beats fixing or replacing a broken one numerous times. Plus, if you get a suitable tranny before breaking your old one, you can recoup a few bucks by selling the old unit.

We'd like to extend our thanks to Ray Clark and George Xenos for their help in completing this install. Now check out the installation here to see how easy it is to give your Pony an extra gear.

Photo Gallery

View Photo Gallery