Overdriven and Understressed

The transmission swap kits, called Transmission Systems at Keisler, are intended to provide everything required to perform the changeover, and to do it with the fewest additional modifications. In many cases, the kits are complete bolt-ins, though some applications require minor floorpan alteration and/or bellhousing alterations. A typical Keisler kit includes the new gearbox, application-specific shifter, custom crossmember (if needed), correct speedometer cable with calibrated driven gear, custom driveshaft, needle-roller-type pilot bearing, reverse-light wiring harness, and hardware. Some kits contain additional items, and pretty much everything else you might need is available.

One of the steps taken at Keisler to ensure proper fitment of swap kits is to create computer modeling of the floorpans of the specific applications. This allows the kit designers to merge gearbox with floorpan on the computer to reveal potential problem areas. This also provides an excellent means of developing swap solutions when fitment conflicts do arise.

This manual-trans floor-shift hump is an exact replica of an original Mopar piece, reproduced by Keisler. This particular one allows an automatic car to be converted to a factory-appearing four-speed setup, but Keisler also manufactures transmission humps to accommodate overdrive gearbox swaps while maintaining factory appearance.

Since the length of both the Tremec TKO gearboxes and the T56 differ from nearly all traditional factory-installed musclecar transmissions, custom crossmembers are required to mount them in older vehicles. Again, Keisler's systems approach includes this aspect of the swap, and bolt-in crossmembers are provided with most kits.

To maintain the original-style side-linkage-type shifter position, Keisler has developed low-profile internal offset shifters to fit the internal-rail gearboxes. A number of application-specific designs are offered, all intended to maintain precision shifting while fitting factory shift consoles. In many cases, combining the proper offset shifter with a stock-appearing shifter handle (also offered by Keisler) can make the swap undetectable from the cockpit.

For those starting with automatic-equipped vehicles, Keisler can provide the necessary stock-type pedal sets to convert to manual trans. Again the opportunity is taken to improve, and some applications use needle-bearings and Delrin bushings for ultra-smooth operation and long life.

Of course, if the transmission is a non-stock length, the driveshaft will also have to be altered. Rather than providing specs, Keisler kits simply include a new shaft, in part because a new larger slip-yoke is required with the updated gearboxes. Each shaft is made from lightweight chromoly tubing, assembled with Spicer yokes and U-joints, and spin-balanced to 10,000 rpm. Standard torque rating is 1,200 lb-ft.

Since the Tremec's smaller ancillary items like the speedometer output and electrical connections for reverse lights and neutral safety are intended for later-model applications, Keisler even provides custom speedo cables and wiring harnesses to further smooth the swap.

As mentioned earlier, Keisler manufactures a broad line of stock-appearing shifter handles, designed to bolt to the custom internally offset shifter to maintain stock appearance. The shifter hole in the floor of this Tremec-equipped '69 Z/28 is unaltered, as is the console.

13. Many of the Keisler kits are designed to retain the stock mechanical clutch linkage, and while hydraulic actuation is required for a few applications, it's optional for most others. Keisler uses a hydraulic throwout bearing that mounts over the input shaft along with a high-quality application-specific aftermarket master cylinder and braided lines. All brackets and hardware for specific applications are included. CC