There’s nothing quite like the crisp gear whine and snap that go with an old-fashioned Muncie four-speed transmission, a powerful engine, the open road and a delightful summer day. However, the downside to a classic straight-drive manual four-speed stick is fuel consumption along with the associated wear and tear. Unless you’re just bent on nostalgia and pumping gas there is surely a better way to get there.
American Powertrain enables you to blend the swift-slippery classic lines of a C1, C2 or C3 Corvette with the great efficiency and function of a modern five-speed transmission. What’s more, you can get this swap done in a weekend if you stay on it.
Let’s begin with the heart and soul of this swap: the TREMEC TKO 600 for street and strip use. The TKO 600 is a popular replacement for outdated straight-drive four-speeds because it is an extremely durable gearbox capable of handling up to a constant load of 600 lb-ft of torque. This means the TKO 600 can handle the twist of most small- and big-block Chevys, not to mention factory LS engines without breaking a sweat.
With the TREMEC TKO 600 you get a 26-spline input shaft, 4616 chromoly gears and shafts, one-piece countershaft, brass cage roller bearings, full factory warranty (American Powertrain extends the factory TREMEC warranty to two years), with 2.87:1, 1.89:1, 1.28:1, 1:1, and 0.64 ratios. These features make the TREMEC TKO 600 from American Powertrain perfect for the commute, weekend cruising or all-out drag or road racing.
The Pro-Fit TREMEC TKO 600 five-speed transmission kit is engineered to fit your classic Corvette chassis and engine without special modifications. Everything you’re going to need is provided in the American Powertrain Pro-Fit kit.
Here’s what you get:
• ProShift Corvette Shifter Conversion - Original four-speed shift position
• White Lightning Shifter Mechanism - Solid billet construction, bias adjustable
• Seamless DOM Driveshaft Assembly - Race balanced, solid U-joints
• Billet Face Flange Yoke - Bolts in for easy installation. This is a patented difference in the American Powertrain kit vs other Corvette TKO kits on the market you have to lower the engine on those to install
• Transmission Mounting Bracket — Bolt-in powdercoated steel
• Transmission Mount – Polyurethane
• Pilot Bearing - Stainless rollers, grease pre-pak
• Reverse Light Harness – Weatherseal
• Speedometer Conversion - Mechanical or electronic
• Console Shift Pattern Plate
• Hardware, Instructions, Warranty and Customer First Extended Hours Tech Support
American Powertrain makes it easy to order and install a complete TKO 600 and hydraulic clutch system all in one stop. And that’s because you have matched components carefully engineered to work together in a classic C1, C2 or C3 Corvette. Once all of these components are on your doorstep and unpacked in the garage, you can carefully inventory the parts and plan out the five-speed swap and hydraulic clutch installation in a weekend. Vette
1. If your engine connected to a four-speed it will have a clutch pilot bushing like this one, which will need to be removed. You may remove the bushing or bearing with a slide hammer puller or pack the cavity with grease and “hydraulic” the bushing or bearing out.
2. We strongly encourage replacing the clutch pilot bushing with a bearing for smooth operation. Sparingly pack the bearing with wheel bearing grease. You don’t want grease in contact with the clutch disc or pressure plate.
3. The block separator plate from American Powertrain is installed next as shown. Make sure you have installed the engine block dowel pins and are using Grade 8 bolts, such as those available from ARP.
4. We’re using ARP flywheel and clutch pressure plate bolts lubricated with ARP’s Ultra-Torque Fastener Assembly Lubricant. Never install fasteners dry.
5. Our American Powertrain flywheel is properly indexed and installed. Dress the mating surfaces if there’s any indication of binding.
6. The flywheel bolts get torqued to 60-65 ft-lb in crisscross fashion. Begin by hand tightening the bolts, making sure the flywheel is properly seated.
7. The bellhousing alignment must be checked to ensure proper clutch function and to eliminate any side-loading of the TKO 600’s input shaft. With the flywheel and QuickTime bellhousing installed, set up a dial indicator as shown, centered at 12 o’clock (needle at zero) and slowly turn the crank. Record the needle measurements at the 3, 6 and 9 o’clock positions. The readings at 12 and 6 o’clock are vertical runouts. Allowable runouts within American Powertrain specifications require no correction. Runouts outside of allowable limits must be corrected with offset dowel pins in the engine block. Keep your measurements for warranty issues if needed.
8. Our flywheel has been cleaned thoroughly with brake cleaner and is ready for the clutch disc. The clutch disc is centered with a clutch alignment tool.
9. The pressure plate is installed next and centered on the clutch disc. Bolts get ARP bolt dressing and are installed and snugged until the pressure plate is seated, then torqued to 36 ft-lb in a crisscross fashion in one-third values up to the final spec.
10. Once the pressure plate bolts have been tightened to specifications, the clutch alignment tool is removed.
11. Our American Powertrain clutch and pressure plate are properly installed. We’re ready for the QuickTime steel bellhousing.
12. Installation of the American Powertrain hydraulic clutch slave cylinder can be very tricky, which calls for precise measurements between the bell and the clutch fingers. The measurements determine clutch cylinder depth. Diaphragm style clutches require constant pressure against the fingers.
13. The Hydramax clutch kit from American Powertrain enables you to convert to the smoothness and ease of hydraulic clutch power in the time it takes to put a TKO 600 into your C1, C2 or C3 Corvette. The kit comes complete with master cylinder and reservoir, hydraulic lines, shims, release bearing/slave and all hardware.
14. The Hydramax installation begins with the removal of the front bearing retainer at the 2 o’clock position, which is where the release bearing/slave cylinder will be secured.
15. Loctite is applied to the threads of the replacement bolt/stud to ensure fastener security.
16. The Hydramax release bearing/slave cylinder is secured to the front bearing retainer as shown here.
17.Measurements are noted here at the release bearing to compare earlier measurements at the bellhousing and clutch fingers, then, the release bearing is adjusted accordingly.
18. The QuickTime bellhousing has been installed and is ready for transmission installation.
19.The shim thickness between the slave cylinder and transmission is determined with this micrometer. We add shims to increase clutch penetration and subtract them to decrease penetration.
20. The correct number of shims has been installed on the front bearing retainer as shown, which will give us the right release bearing depth at the clutch fingers.
21. The Hydramax release bearing is positioned on the bearing retainer. Our next step will be to check transmission-to-clutch fit.
22. The Hydramax clutch master cylinder instructions enable us to determine the correct number of shims necessary at the firewall to achieve proper pedal height and function. We need 0.2 inches of shims based on these calculations.
23. The Pro-Fit kit from American Powertrain for five-speed transmission kits includes the ProShift shifter that relocates the shifter to the Corvette’s original four-speed location; White Lightning shifter mechanism; Seamless DOM driveshaft assembly, Billet Faced Flange Yoke (bolts in); Transmission mounting bracket; Urethane Mount; Clutch Pilot Bearing; Back-Up Light Harness; Speedometer Conversion (Mechanical or Electronic); Console Shift Pattern Plate; and Hardware, Instructions, Warranty and Customer First Extended Hours Tech Line.
24. This TKO 600 Street and Strip five-speed cutaway for GM is 600 lb-ft constant load rated unmodified with a 26-spline input shaft, 4616 chromoly gears and shafts, one-piece counter shaft, brass cage bearings, with a full factory warranty and ratios: 2.87:1, 1.89:1, 1.28:1, 1:1, and 0.64 overdrive. This is the optimum TKO 600 street/strip box.
25. The TREMEC TKO 600 is carefully lined up for installation. This is a fit-check to ascertain hydraulic clutch release bearing fit where we are putting a slight load on the clutch fingers (diaphragm).
26. A closer look at the Hydramax release bearing and slave cylinder show penetration into the QuickTime bell. The hydraulic lines will be fed through the left-hand side of the bell where a clutch fork normally goes.
27. The TKO 600 is slowly bolted to the bell by running the bolts down in increments. Once seated at the bellhousing, the release bearing needs to be checked at the clutch diaphragm for proper fitment.
28. There’re several things your smartphone can do, including interacting with the transmission experts at TREMEC. The TREMEC Toolbox mobile app is like four separate apps all in one. Vehicle Speed and RPM Calculators allow users to determine vehicle speed in any gear at a given rpm, or engine speed in top gear at a given mile-per-hour. Gear ratios can be entered manually or with preloaded transmission profiles that include not only TREMEC transmissions, but other popular transmissions as well. Calculations depend on tire height, and for that a Tire Size Calculator can be used to convert P-metric tire sizes into tire height in inches.
Photos by Jason Scudellari