Miles Cook
August 13, 2006
Ron Morris Performance's AOD shift-linkage kit makes the connection between a stock C4 shifter and an AOD transmission. Recall that a stock Mustang floor shifter has three detents, the same number as found in an AOD, since there isn't a detent in a stock AOD for Second gear.

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.

During an AOD conversion at the Ron Morris Performance shop, this is what was removed from a car prior to installing the new parts. Shown here are the stock C4 trans, crossmember, driveshaft, flexplate, dipstick and tube, block-off plate, starter, and transmission mount. A stock driveshaft can be reused once it's shortened and fitted with an AOD yoke. The stock C4 mount and starter can also be used with the AOD trans and crossmember.

Parts Needed for a Four-Speed to T5 Conversion

  • T5 transmission
  • Top Loader bellhousing-to-T5 adapter plate
  • T5 crossmember
  • T5 shifter and handle
  • C4 transmission mount
  • T5 yoke

    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.

    For installing a T5 in a vintage Mustang already equipped with a manual transmission, these pieces from California Pony Cars (CPC) will get you down the road. Shown here are CPC's T5 crossmember, its adapter plate, and a transmission mount. Also here is a vintage-style shift handle that bolts to a stock late-model T5 shifter. At the bottom is a T5 yoke that needs to be installed on an existing driveshaft, which in turn, needs to be shortened, usually about 1 inch.

    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

  • T5 transmission
  • Late-model 5.0 T5 bellhousing
  • Clutch
  • Manual-transmission pedal set
  • Clutch cable kit
  • T5 crossmember
  • T5 shifter and handle
  • C4 transmission mount
  • T5 yoke

    The CPC adapter plate drops right onto a stock Top Loader four-speed bellhousing after two holes are drilled in it to accept the plate.

    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
    First 2.32 2.78 3.35 2.95
    Second 1.69 1.93 1.99 1.94
    Third 1.29 1.36 1.34 1.34