Installing A New Five-Speed TKX Without Cutting The Car

When it comes to driving a classic hot rod, being able to rack up as many miles as possible is something we all wish we could do more often. However, life usually dictates that other things get our attention before getting behind the wheel. When we do get some much-needed seat time, the rumble of a roaring V8 can be a soothing sound as it carries its musical tune. But what if that musical tune gets to be…well…shall we say…overbearing?

I know what many of you are thinking, “how can a rumbling V8 get annoying”? If you built your hot rod with the idea that having a true “red light” machine is perfect, then you likely have a set of steep gears. We have all fallen victim to the idea that we want a true stoplight machine that will smoke the tires at will. Initially, we are typically willing to sacrifice any long-distance cruising for the pleasure of having a numerically higher rearend gear ratio that is best suited to short trips. But is it possible to have steep gears and a long-distance cruiser? The folks at Silver Sport Transmissions (SST) say yes, yes, it is, by installing a five-speed TKX.

For this install, the car owner wanted to upgrade to a hydraulic clutch. This is not something you need to do, but it really makes the pedal much easier on the leg when stuck in traffic.

Having a car that performs well — during short jaunts and long cruises — is much more viable than it was a couple of decades ago. Thanks to the availability of the five-speed transmission, you can have a multi-purpose car. I know what you’re thinking, “I really do not want to cut the floor of my car to add a five-speed transmission.” I get that, I wouldn’t do it either. But the folks at SST gave us the opportunity to follow along as they install a new TREMEC TKX into a Chevelle.

Throw Away The Flaming Hacksaw

The first thing we learned is there is no cutting required. Dimensionally, the TKX is smaller than its predecessor, the TKO. There is no arguing the TKO is a terrific high-performance transmission. But its overgrown size kept many from considering it.

“The GM A-body is where this transmission really shines,” states Misty McComas of Silver Sport Transmissions. “The GM A-body owners could not get around cutting their transmission tunnel and it was major tunnel surgery. The TKX will fit ’68 through ’72 Chevelles right out of the box by flipping the shifter 180 degrees; this simply requires the removal of six bolts, rotating the shifter mechanism, and reinstalling the bolts. SST even does this for no extra charge! If you want a shorter throw, the STX (Street/Track/Autocross) shifter makes for a nice upgrade providing a 12-percent shorter throw and crisper side-to-side spring biasing.”

Not only is the TKX smaller than the TKO, but shift quality has also been improved. It’s probably not something you really care about, but this is accomplished via multi-cone, high-performance, strut-type synchronizer, and hybrid (sintered bronze and carbon) synchronizer rings. What’s more, the TKX can comfortably survive engines delivering 600 lb-ft of torque. But I know what you’re thinking, “a great product is useless if it doesn’t fit.” We are here to verify that it does.

The exact steps to install an SST-prepped TKX five-speed transmission in your classic cruiser or hot rod (you can find a PerfectFit kit for many Ford, GM, and Mopar cars) are different for all cars and each kit can be installed by the average enthusiast in a couple of days. For that reason, we will not get in-depth with this install into a ’72 Chevelle. We just want to show you what to expect before you fork out any money. As a side note, SST also offers six-speed overdrive manual-shift transmissions (some cutting required) and even an overdrive automatic if you want a shift-itself gearbox.

The TKX has provisions for backup lights, neutral safety, and electronic and mechanical speedometer. The transmission comes with wiring pigtails so you can connect to your factory harness for the backup lights. As far as the speedometer, you get a pigtail to use if you have an electronic speedometer, and a cable-driven gear housing if you're using the car's factory speedometer cable. The neutral safety switch can be spliced into your starter circuit between the ignition switch and the starter solenoid if you choose to use that feature.

If your car is currently utilizing an automatic transmission, SST offers complete kits that are designed to convert automatic cars as well. If needed, kits are available for many cars that include pedals. The company can even set you up with a hydraulic clutch assembly that offers modern efficiency and smooths out the shifting chores. Finally, the SST PerfectFit five-speed kit comes with a shifter that is correctly positioned for the car you have. This is a big deal. Imagine buying a new five-speed someplace else and then having to cut a hole in your floor for the shifter. In case you are wondering about gear ratios, the TKX comes in a choice of two gearsets (wide: 3.27, 1.98, 1.34, 1.00, 0.72, and close: 2.87, 1.89, 1.28, 1.00, 0.81 or 0.68).

Old-School Connection For A  New Five Speed

Another aspect about the TKX five-speed that is appealing to classic car owners is the included provision for a cable-driven speedometer. Previous TREMEC transmissions required the use of an electronic speedometer or an adaptor for connecting the cable. This is something that is a welcomed addition to the TKX.

Many enthusiasts felt that previous TREMEC transmissions were a bit clunky when shifting. That issue has been addressed via multi-cone, high-performance, strut-type synchronizer, and hybrid (sintered bronze and carbon) synchronizer rings. Having double cones at all gear changes enables power shifting as well as reduced dynamic shift effort. Also, the gears have been case-hardened and shot-peened for strength. The new transmission makes it virtually a must-have upgrade.

TKX install

As you can see, in this application, the stock crossmember is reused. It just needs to be moved back a few inches.

A Better Look

We were given the chance to follow along as the folks at SST took the time to drop one of the TKX-equipped Perfect Fit five-speed kits into a customer’s Chevelle. For this install, the car was pulled into the shop with a four-speed under the floor. This means the installation was much easier than would have been in a car with an automatic. This is because we didn’t need to install pedals and other manual-specific parts. The installation was really straightforward.

If your car is not equipped with a four-speed, you will need to modify the floor by installing a reproduction four-speed hump. Yes, I said there would be no cutting, but if your car currently has an automatic and you’re switching to manual, you will need to cut the floor and add the hump. Since you would need to do this if switching a factory four-speed, to me, it’s a wash.

With the five-speed transmission easily slid into place, you can see that no modifications were made to the floor, and the factory shifter location is used. Keep in mind, SST modifies the TREMEC to make fitment this easy. If you buy a TKX from someplace else, the shifter position might not be in the right location for your car.

As I previously mentioned, this article is by no means covering all aspects of the install. It does, however, give you some insight into what you can expect. If you are planning an upgrade to a Silver Sport Transmission’s five-speed, plan on the install taking the better part of a busy weekend. I do need to mention, while we had a lift at our disposal this time, you can complete this upgrade utilizing a floor jack and jackstands.

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About the author

Randy Bolig

Randy Bolig has been working on cars and has been involved in the hobby ever since he bought his first car when he was only 14 years old. His passion for performance got him noticed by many locals, and he began helping them modify their vehicles.
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