The real joy of owning a muscle car is driving it. Sports car owners who want to get the most out of their cars often drive to remote car shows or other events, but without an overdrive transmission, a long trip on the highway becomes tedious. If the car has a performance rear axle ratio, it is even worse. I love the sound of a high-speed V8 as much as any other man, but a steady 3600 RPM for a solid three hours with a loud exhaust tires. Most of us have gotten used to being able to carry on a conversation and / or listen to the radio on long trips, and we wish we could go through at least a couple of gas stations without stopping to fill up! An overdrive transmission solves those problems and provides many other benefits as well.
The Tremec TKO is a five-speed manual with overdrive that is ideal for adapting to classic muscle cars from the 1960s and 1970s. With your choice of an overdrive ratio of 0.82: 1, 0.68: 1, or 0.64: 1 depending on the model, you can really bring those revs down to a manageable number. A lower engine speed on the highway offers several advantages.
First of all, as already mentioned, there is the noise level. If you have a 3.73 axle ratio with a 235 / 60-15 (26.1 “high) tire, 75 MPH equals 3600 RPM with a four speed no overdrive. The TKO-600 with a 0.64 fifth gear: 1 (the popular version) will reduce that 3600 RPM to a quiet 2300 RPM at the same 75 MPH. The sound level at 2300 RPM is much easier on the ears after a couple or three hours than it would be 3600 RPM! !
Another benefit of the lower RPMs that I already mentioned is better fuel economy. All things being equal, the engine will obviously use less fuel at 2300 RPM than at 3600 RPM, but with a car engine that has been built for performance, there is another factor that comes into play. At 3600 RPM, some 4-barrel carburetors may have the secondary ones partially open. If you have a steeper axle ratio, the secondaries are even more likely to be open at highway speeds. With a 4.10 rear gear, that 75 MPH number I’m using results in almost 4000 RPM with a no overdrive transmission. By this time, many carburetors will have the secondary barrels discharging fuel. Lowering the RPM needed to navigate the highway will lower your throttle angle, close the secondaries, and make a big difference to your fuel economy. In fact, I’ve seen fuel mileage double on the highway by installing a TKO, due to the fact that I can navigate without having the secondaries open!
Engines wear out faster at higher RPM. In simplified terms, each engine has a service life consisting of a certain number of revolutions, barring abuse, neglect, or catastrophic failure. If you use less of those revs each time you drive 200 miles to a car show, your $ 5,000, $ 10,000, or even $ 20,000 engine will last longer. So will everything attributed to it that rotates with the motor. Your alternator, water pump, mechanical fuel pump, power steering pump, and AC compressor will spin at lower RPM on the highway and their life will increase.
High-performance engines produce more heat than normal passenger car engines. Many muscle cars have heat problems due to high rpm on the road. Lowering RPM with an overdrive can lower engine temperature and prevent overheating on long trips.
The intangible advantage of all of the above is that overdrive will allow you to drive your muscle car more. It can and will be more likely to drive you to more distant car shows, or even on vacation! Overdrive lets you enjoy your car more by driving it to places you wouldn’t consider going with your 4-speed (or 3-speed automatic) cranking the engine at 3600 RPM.
The TKO is quite strong for most muscle cars. It is rated for 500 or 600 lb.-ft. continuous input, and those numbers are very conservative. There are a lot of cars that run much more than nominal torque with the TKO, and failures are rare. Although I cannot officially endorse the use of the TKO in an application that exceeds the torque capacity, I can tell you from experience that many people have done it and had no problem, even in race conditions.
The Tremec TKO will lower the noise level on the road, increase fuel consumption, increase the life of your engine and everything attributed to it, could reduce or eliminate temperature problems and allow you to drive your car to places where I would not do it. with an old four-speed. It is stronger than the old Muncies, T-10, Toploaders and A-833. Versions are available that will bolt directly to a common GM or Ford 4-speed steeple, and custom Mopar steeples are available to fit a TKO to a Mopar small-block, big-block, or late-model Hemi. All in all, it’s an ideal transmission for a highway-driving muscle car. For more detailed information on TKO specs and options, take a look at my other articles in this series.