TREMEC TKX 5 speed, tremec transmission

Gimmie Five! An Overview of the New TREMEC TKX 5-Speed

Does it get any better than being pushed back in your seat as you roll through the four gears of your favorite muscle car? Yes, it does – by rolling through five gears!

You’d be surprised at how one more gear changes the way your car drives. Shifting into that fifth gear overdrive immediately drops the engine rpm and you feel your car settle into a smooth cruise mode. It’s amazing how the lower rpm on a long drive helps both the car and you relax and just enjoy the drive.

TREMEC TKX 5 speed, tremec transmission

The all new TREMEC TKX five-speed manual transmission is the company’s first transmission designed specifically for the aftermarket. The new housing is sleeker for better fit and internally the gears and assembly have been beefed up to handle the higher torque and rpm range.

One of the most popular five-speed transmissions used in hot rod conversions comes from TREMEC. You’ve seen and read about their line of TKO 500 and 600 transmissions as well as the beefier Magnum six-speed. The company has been producing manual transmissions since 1964 and even produced Ford’s Toploader trans for years. In the early-’90s, TREMEC acquired the manual trans business of BorgWarner which included the T5 and T56, both of which remain popular trans swap as well.

In the mid-’90s, thanks in part to the popularity of Mustang racers and enthusiasts beating up the T5s, TREMEC introduced the TR-3550 transmission, which was an instant hit for the Fox-body crowd. There were also handful of innovative hot rodders who modified the 3550 to install into GM muscle cars and other applications. Noting the growing popularity of these five-speed upgrades, the performance division of TREMEC introduced the stronger TKO series in about 2004 which has remained the most popular five-speed conversion trans…until today.

Late last year, during what should have been the 2020 SEMA show, TREMEC introduced their all new TKX five-speed to the performance world. This was their first transmission developed and aimed directly at the performance aftermarket rather than an OEMs, and it shows. The case is noticeably sleeker for improved fitment, especially in older vehicles. Plus, the internals were redesigned to hold even more torque capacity! Getting a huge OEM supplier like TREMEC to listen to what a bunch of hot rodders have to say is rare these days, but according to Mike Kidd, their aftermarket business manager, “we listened to our customers, combined their suggestions with our OEM technology, and strengthened our aftermarket lineup with the all new TKX.”

TREMEC TKX 5 speed, tremec transmission

Notice how much more space is available below the shifter on the TKX (right) compared to the TKO (left). Since this was developed specifically for the aftermarket, no extra mounts were required. The TKX does measure the same length at 23.75-inches and is a couple pounds lighter. Shown together, you can really see the difference in the housing, especially the top and its new, slender housing.

Sidebar – Bowler Transmissions TKX LS Kit

Bowler Transmissions is a TREMEC Elite Dealer and has been working with the company for years on transmissions like the popular TKO and Magnum series. They’re excited about the new TKX and are already test fitting the transmission in different applications and offering it in their systems. We asked them what they thought about the new gearbox.

“With our limited time with this new transmission we can already say that it is a great improvement from the original TKO. The streamlined case design is a much-needed upgrade that allows the transmission to fit a wider range of vehicles without the need for additional modifications to the tunnel. There will be some instances where some cars will require a modified opening for the shift lever since the shift stub is located on the top center of the tailhousing rather than the stand-alone side-mounted lever that was used on the Muncie and Toploaders.

“As far as functionality, the TKX shift feel is much smoother and more positive than the TKO. With the new multi-cone blocker ring design, similar to the Magnum, the higher-rpm shifting happens with ease. We feel this transmission will be the perfect solution for anyone with a higher-revving engine that doesn’t want to make the modifications required to fit a Magnum six-speed.”

TREMEC TKX 5 speed, tremec transmission, bowler transmissions

Bowler has already put together a complete TKO package for LS engines producing up to 550hp and lb-ft. It will work with all six- or eight-bolt cranks for LS and LT engines and comes with the close-ratio TKX along with a cast aluminum bellhousing, Tilton 6000-series throwout bearing, RAM single-disc clutch kit, and billet steel flywheel. A roller pilot bearing, trans mount and Royal Purple Synchromax fluid are also included. Plus, they can provide a model-specific crossmember and hydraulic master cylinder for your application.

We figured it was worth a closer look at the TKX to see why there was so much buzz about the new five-speed and how it would benefit the builders and drivers of classic cars. As we mentioned, the first thing you notice about the transmission is its smaller case and rounded top. The number-one criticism from vintage muscle car owners was that they’d have to cut the floor of their original car to get a TKO to fit properly. TREMEC’s engineers set out to change that with a new, more slender case that will fit in the older tunnels much easier and without any slicing.

But there’s more to the new case than its smaller size. Notice that there is no longer an access panel on the top, as the TKX is now assembled from the rear of the case, making the housing a more rigid foundation to secure the gears and shafts. There is also a beefy mid-plate sandwiched between the main case and the shifter housing, which diminishes any deflection of the main shaft during moments of high torque.

TREMEC TKX 5 speed, tremec transmission

Note the electronic speed output on the passenger side while the driver’s side has a mechanical output. The shifter can be positioned in three spots and notice the thick mid plate between the two main housings. This adds considerable support to prevent deflection of the shafts during huge loads and rpm.

Another benefit of the redesigned case allowed the engineers to focus on reducing noise and vibration, which was considerably lowered thanks to the fresh three-piece ribbed aluminum housing. To ensure a universal fitment, there are still three positions for the shifter placement. Also note the added clearance under the shifter housing, which was opened up by removing OEM spec mounts. The crossmember mount remains in the same location and the length of the trans remains even with the TKO series at 23.75-inches.

The all new housing is great, but TREMEC didn’t stop there. They wanted to beef up the internals to keep pace with the ever-increasing rpm range and torque ratings of modern engines. The new trans is rated at 600 lb-ft of torque with shifts taking place at up to 7,500rpm. To produce trouble-free shifts at that kind of rpm, the engineering team did quite a bit of work on the mechanics and materials behind the shifts.

TREMEC TKX 5 speed, tremec transmission

This cutaway illustrates some of the improvements TREMEC designed into the TKX to increase its strength and ability to shift at higher rpm.

For starters, they were able to increase the width of the gears, which is key in handling more torque due to the larger surface area across the teeth. Each gear is made from ASTM 4615-grade steel, and then case hardened and shot-peened for strength and durability. They also improved the synchronizers, which are responsible for adjusting the different shaft speeds during a shift. The TKX incorporates a hybrid material of sintered bronze and carbon for the synchronizer rings along with revised multi-cone synchronizers.

Sidebar – American Powertrain

American Powertrain was formed to help muscle car and classic truck owners enjoy the benefits of a modern, manual overdrive transmission in their rides. They’ve sold thousands of TREMEC transmissions and kits featuring their custom systems for a complete installation. The company is another TREMEC Elite dealer that is excited about the all new TKX and its features for the market.

“The biggest thing about the new TKX to most enthusiasts is the improved fitment in the tunnel. GM A-body fans will be really excited about not having to cut into their floors, along with many other applications.

“The increased torque capacity and high rpm range of the trans are needed to keep up with the increasing power and rpm span of the modern engine platforms being used today. Plus, the work TREMEC put into the shifting effort and feel is something that improves the whole driving experience even more than the simple pleasure of driving a stick.”

TREMEC TKX 5 speed, tremec transmission, American Powertrain

F-100 fans will be excited to see the Pro-Fit TKX kit for ’67-’79 models from American Powertrain. The kit is supplied with a seamless, balanced driveshaft, their Revolution shifter mechanism to locate the shifter for bench or bucket seats, their X-Factor crossmember and mount, hardware and speedo conversion. They will also help you select the best clutch assembly and Hydramax hydraulic clutch for your application.

From a touchy-feely shift point, TREMEC added a ball detent design on each of the three shift rails to improve the touch and precision of each shift. They added chamfers in the gates and selector finger to produce solid, secure shifts on the track or when just cruising. There is also an internal interlock to prevent gear clashing at high rpm.

With all of these internal and external updates, you can see how this trans was designed for the aftermarket. Out of the box, the five-speed is ready to replace an old Muncie, Toploader or even some Mopar sticks. There are close-ratio and wide-ratio options with the close-ratio starting at 2.87 and second at 1.89, while the wide ratio kicks off with a 3.27 and 1.89 ratio. The fifth gear ratios range from .68, .72 and .81. GM Models use a fine, 26-spline input shaft, as do the Fords, with one model available sporting a 10-spline for Ford fans.

TREMEC TKX 5 speed, tremec transmission

Note the one Ford model offered with a 10-spline input shaft, the rest feature a ‘fine’ 26-spline shaft. Gear ratios are listed for the wide (3.27 first) or close ratio (2.87 first). Be sure to consider the rearend ratio and tire size when selecting an overdrive ratio, which is available in .81, .72 or .68.

To further cover their bases, the new TKO boasts a gear-driven and electronic speedometer output along with a backup light switch and neutral safety switch. Is there anything they didn’t think of on their next generation TKX? Not that we can think of, but if something comes up you can be sure that one of their Elite dealers like American Powertrain or Bowler Performance will offer up a solution!

Be sure to stop by the TREMEC trailer at a Goodguys event this year to see the new TKX. As a manufacturer, the company does not sell direct to consumers, but has a network of dealers like Bower Performance, American Powertrain, and others who you can connect with to learn about purchase and package options.

Todd Ryden is first and foremost a car guy and admits to how lucky he is to have been able to build a career out of a hobby that he enjoys so much. He’s owned muscle cars and classics, raced a bit and has cruised across the country. With over 25 years in the industry from the manufacturing and marketing side to writing books and articles, he just gets it.