Changing Your Ford Transmission - Overdrive Transmission Swap Guide
Thinking about an overdrive-transmission swap for your vintage Mustang? This look at the parts and procedures is a good place to start.
There's lots of good news with this. You can retain a car's factory clutch linkage and bellhousing because California Pony Cars offers an adapter plate that allows you to join a T5 with a stock Top Loader four-speed bellhousing. The stock bellhousing is modified with two holes so it will accept the adapter plate.
From this point, the T5 installation is virtually a bolt-in. A car's existing clutch can be used along with a stock Fox Mustang or late-model aftermarket shifter. Sources such as Mustangs Plus or National Parts Depot also offer vintage-look shift handles that bolt to a T5 shifter. You could also use the stock late-model T5 shift handle and knob if you want.
To wrap up a T5 swap, the tasks at this point are about the same as an AOD conversion. You'll need to install a T5 yoke on the driveshaft and shorten it a predetermined length, again around 1 inch.
Parts Needed for a Four-Speed to T5 Conversion
Automatic to Five-Speed Manual
Since the vast majority of vintage Mustangs were equipped with automatic transmissions, it stands to reason that many enthusiasts will want to convert to a manual trans, which usually meant a Top Loader or T-10 four-speed back in the day. Frankly, we think going from, say, a C4 to a Top Loader is a complete waste of time these days when it's the same amount of work and only a little more cost to go to a T5, especially when you factor in that you can get a freshly rebuilt T5 from D&D Performance for $999.
Swapping from a C4 to a T5 is an excellent upgrade, and the task is similar to going from a four-speed to a T5. However, since a car with an automatic doesn't have a factory clutch linkage, there's an alternative that works perfectly for this swap. You can also go this way with an existing manual-trans car if desired.
Of course, the most obvious thing needed for this conversion is a manual-transmission pedal set with a clutch pedal. You'll also need a complete clutch setup with the correct flywheel, as well as a late-model T5 bellhousing and clutch fork. Where this swap differs compared to cars already equipped with a stock clutch linkage is that the best way to go is a cable system, similar to what's used in a late-model Fox 5.0. Both Ron Morris Performance and DB Performance Engineering offer a clutch-cable conversion designed for vintage Mustangs. The DBPE system takes care of two issues at once by offering a complete pedal setup along with the cable, while the RMP system is an excellent option as it works without having to drill holes in the firewall. RMP also offers a corresponding clutch pedal to work with its cable system, though you'll still need to procure a pedal setup.
Other than the late-model T5 bellhousing, pedals, and cable kit, the rest of the swap is the same as the conversion from four-speed to T5. That is, you'll need the same crossmember, shifter, C4 transmission mount, and T5 driveshaft yoke. You'll also need to shorten the driveshaft about 1 inch.
Parts Needed for an Automatic-to-T5 Conversion
Manual to Four-Speed Automatic
Though not likely done very often, it's possible to convert a car from a manual transmission to an AOD. The needed parts are basically the same as going from a C4 to an AOD, although you'd likely want to get an automatic brake pedal. A radiator designed to work with an automatic and an auto-trans shifter are required. Everything else listed for an AOD swap remains the same.
Four vs. Five
One of the biggest benefits of a T5 over any standard four-speed manual is that it has an overdrive (less than 1:1) top-gear ratio. However, a standard Fox 5.0 or Ford Racing T5 "Z" trans (PN M-7003-Z) also has a lower (numerically higher) First gear ratio as well, which, of course, means better acceleration in First gear. In a car with a 3.25 rear-axle ratio, the final drive with a four-speed and its 1:1 top gear is 3.25. Add a five-speed to the mix with a typical 0.68 overdrive ratio and the final drive is a dream on the freeway with a ratio of 2.21 (3.25 x 0.68 = 2.21). The chart below further illustrates what we're talking about. The numbers are also similar for AOD conversions.
|Close Ratio||Wide Ratio||T5||FRPP T5Z|