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Keisler Introduces a Complete G-Body Five-Speed (or Six-Speed) Swap

Bob Mehlhoff May 9, 2005

We get a constant flow of e-mail from CHP readers asking about the availability of a kit to install a five- or six-speed manual trans into a G-body. Based on a rear-wheel-drive configuration, GM produced these mid-size full-frame cars from 1978-88 (depending on model) as A-bodies (1978-81). From 1982-88, they were known as G-body platforms. Regardless of reference, there is no question that they're a great alternative to the high-priced musclecars of the '60s. Since GM made only a handful of these cars with manual transmissions during the late-'70s, today, gathering old GM parts to make the conversion is just about impossible. Even at that, you'd have to find an overdrive transmission designed to withstand modern power. Well, there's good news.

Keisler Automotive Engineering has just released a complete kit that includes factory-appearing clutch and brake pedals and most of all the other parts you'll need to convert your automatic car to a fun-driving manual-tranny ride, be it a five-or six-speed Tremec transmission. Last year, we featured Keisler's swap kits for Camaros, Novas, and Chevelles in our June and July issues. During the Hot Rod Power Tour 2004, we got to drive several cars with Keisler's kits, including its awesome '65 Maximum Overdrive Corvette and Don Turner's sleeper COPO clone '69 Chevelle (Oct. '05). These cars drove as though they came from the General equipped with the modern overdrive due to Keisler's system engineering approach to transmission swaps. Starting with a new Tremec TKO 500/600 five-speed or T56 six-speed, Keisler completely redesigns the shifter mechanism, case, and mounting configuration to allow the transmission to properly retrofit the body style, and places the shifter position in the correct factory location-a very important point for most owners.

The company also includes a custom-welded box-construction crossmember, Spicer chromoly steel lightweight driveshaft, speedometer cable and driven gear, isolator mount, roller pilot bearing, hardware kit, and illustrated instructions. Its patented internal offset shifter with removable billet shifter mechanism actually fits within the original floor tunnel-a feat unachievable with a bone-stock Tremec TKO. Clearly, Keisler has set the standard for Tremec swaps.The featured '87 El Camino for the installation belongs to Jim Loveday of Knoxville, Tennessee. Originally equipped with a 200-4R overdrive automatic, Jim had longed for more performance and a bit more excitement to go with it. He wanted a manual transmission with overdrive to put more power to the ground and get more control over engine rpm while still having the benefits of quiet, low-rpm highway cruising. Jim opted for Keisler's 550hp five-speed kit, which is based on the Tremec TKO500 and GM ZZ4 crate engine. With the ingredients in place, he took the car to Keisler's local installation facility, B&M Automotive, where owners Bob Marshall and Tom Carden took care of the upgrade.

Because Jim's car was an automatic, the changeover to the straight shift required more parts than just the five-speed kit. Again, Keisler had prepared all of the requiredparts to make the swap a straightforward affair. This included: a new super-duty titanium-aluminum 11-inch bellhousing, a flywheel, a modern pedal effort clutch, a clutch and brake pedals, a complete hydraulic bearing kit with a direct-fit master cylinder, a chrome shifter handle with a knob, and a boot and trim ring. With the car on the rack, the entire swap-from removing the exhaust, automatic transmission and shifter to installing the complete five-speed kit with accessories-took 14 hours to complete. Follow along as Keisler and B&M change this lazy grocery-getter to a performance street hauler.


The conversion begins with the Keisler five-speed kit, which is based on a new Tremec TKO500. Keisler custom-engineers the transmission to fit the car body properly for both manual- and automatic-equipped cars with bench, as well as bucket seats.

Keisler has even reproduced a super-duty version of the highly sought-after "621" 11-inch clutch housing. Using the newer titanium-aluminum alloys with thick walls, this bellhousing won't crack under reasonable pressure. The modern CNC machining produces a high-precision, perfect-fit part. This replaces the existing four-speed bellhousing and is a great way to upgrade from a 10.5-inch clutch to an 11- or 12-inch pressure-plate assembly. Chrome and Chevy Orange powdercoated versions are also available.

A new billet or cast-steel flywheel is supplied in place of the flexplate. Keisler supplies high-quality computer-balanced diaphragm pressure plates to ensure modern pedal effort and vibration-free performance under high-torque loads. Always use new flywheel and pressure-plate bolts and torque to specifications.

Keisler has designed a direct replacement hydraulic clutch actuator kit for the old-style mechanical linkage. The original mechanical linkage method doesn't provide any clearance for headers and is difficult to install. Keisler's hydraulic kit is a clean solution, offering a single hydraulic line that runs from the master cylinder on the firewall to the hydraulic throw-out bearing mounted on the transmission. The system is designed for over a million cycles and harsh conditions.

Keisler designed a new series of shifter handles for HOT ROD 1, the all steel '69 crate Camaro. This handle is the standard issue for the G-body kit...

...It features Keisler's logo, a triple-plate chrome finish, and a black or white knob. A high-quality rubber shift boot and stamped chrome trim ring is also included.

The exhaust is removed, and then the automatic transmission, shifter linkage, and oil cooler lines are also taken out. Without the oil cooler lines, the engine will run cooler--another added benefit of the manual transmission swap. The automatic carpet will be retained, as will the split bench seat. Keisler has different shifter positions and handles for bench and bucket seat applications.

The hole for the shifter is marked and cut. If ever needed, it is easy to return the car back to automatic.

The roller pilot bearing that supports the input shaft goes on the crankshaft without machining and is a big improvement over the oil-impregnated bronze bushing. Keisler uses a large-diameter roller for high strength.

The billet-steel flywheel is installed with new bolts, which are torqued to 60 lb-ft (small-block). It is important to install the correct balance flywheel (i.e. internal or external balance), or the engine will vibrate, resulting in damage. Keisler carries steel and aluminum flywheels for every popular application.

The bellhousing goes on next and is dialed-in to achieve a high-precision alignment from the engine's crankshaft to the transmission's input shaft; it's a requirement for the Tremec's tapered roller-bearing input shaft. Offset dowel pins (Moroso, Mr. Gasket) are used to correct misalignment between the engine and bellhousing. Keisler's kits include instructions on how to perform this procedure, and it offers a $29 indicator toolset as well.

The clutch plate and disc are installed with the special clutch-plate bolts that center the pressure plate on the flywheel. A high-performance, modern diaphragm version of the original Borg & Beck is used here, which provides for comfortable driving even in heavy street-traffic conditions. Pedal effort is easy; you can push it in with your hand.

The transmission is assembled with the hydraulic bearing at Keisler's. The hydraulic bearing's internal spring will keep the bearing in constant contact with the clutch fingers, thus self-adjusting for clutch disc wear and providing a consistent clutch release at the pedal. The hydraulic bearing has a long life, is sealed in several locations from contaminates, is rated for race duty, and has quick releases without lag. In the G-body, this hydraulic kit makes the conversion process from an automatic much easier because it does away with mechanical linkage that is usually difficult to locate and install. If you have a factory stick-shift G-body, Keisler's kit will work fine with it and retains the original mechanical linkage.

The dual-pedal assembly is installed in place of the brake-only pedal. The firewall grommet is removed to expose the factory-drilled hole where Keisler's master cylinder will be installed...

...The hydraulic system offers quiet, smooth operation, and the nickel-plated steel master cylinder is designed for the high heat a performance car may generate. A quality braided stainless steel Aeroquip line with a Teflon liner supplies fluid to the master cylinder. Bleeding this system is a one-person job.

The master-cylinder reservoir is mounted on the firewall for easy access. It includes an internal baffle to prevent fluid from spilling onto the firewall and has a DOT-approved fluid line.

With the bellhousing in place, the transmission is carefully slid forward. The Tremec is sometimes more difficult to fully seat because the input shaft does not flex like a Muncie or Borg Warner T10. Hint: Never use bolts to draw in the transmission; you may damage the pilot bearing. Simply actuate the clutch to release the disc and give the transmission more room to move for alignment.

The crossmember and isolator mount are installed to provide a solid resting place for the transmission and the correct driveline angle. The different mounting pad height and rearward location of the mounting pad on the Tremec precludes use of the original crossmember...

...Keisler emphasizes that the driveline angle must be kept within factory specs to prevent driveline wear. Keisler's crossmember also allows for large-diameter dual-exhaust pipe clearance.

The balanced Spicer chromoly driveshaft is installed. Keisler builds these in custom lengths, and includes one in every transmission kit.

The shifter handle, boot, and trim ring are installed for the finishing touch.

Installing an overdrive transmission makes a huge difference in highway comfort, engine wear, and fuel economy. Keisler illustrates this in its "Best of Both Worlds" speed table. Engine rpm at highway speeds are approximately one-third less. This means 4,000 versus 2,500 rpm with the 0.64:1 ratio OD. You will actually be able to carry on a conversation without yelling! Keisler states most customers report a huge fuel-economy improvement. The company's own Maximum Overdrive Corvette gets 25 mpg on the highway with 3.73:1 gears.


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