The short answer is that the new TKX is the newer, and significantly advanced 5 -speed from Tremec that was specifically designed and built to be the perfect fit in your fun hot muscle car. The long answer specifically talks about each difference, and why it is good, and can be found below thanks to our friends at American Powertrain, who can help you with a complete TKX kit for whatever car you have.

What are the differences? This article is to help you understand the basic differences in the TKO 5-speed and the new TKX that replaces it.

When Tremec designed the TKX they wanted a new design just for the aftermarket. In the past the aftermarket transmissions were based on OEM designs in house. These got tweaks or new tailhousing castings to offer more flexibility for aftermarket use. Tremec listened to customer input over the years and decided to offer a completely aftermarket design from the ground up.

But first let’s talk TKO

The TKO was a great transmission. Based on the TR-3550, it was an OEM design that was used in some 2wd truck applications. Later on, it was used for some OEM Ford Mustang Fox Body applications as well. Soon after it was known as one of the best upgrades you can do for your Fox Body car. It had a rated torque capacity up to 600 lbs/ft of torque, which is one of the reasons it sold so well over the years. It was versatile, with multiple shift positions, dual speedo outputs and it was available in Ford or GM bolt patterns. 26 spline input and 31 spline output for increased strength and capability. But it had one problem: it was square. This made it a tight fit into many muscle car applications. Here at American Powertrain we do what is called “case streamlining”. We machine down the top cover so it provides more clearance into cars such as Chevelles and Mustangs. One of the reasons the TKO was a boxy shape was that it was a “Topload” design, meaning the gears came in from the top. This made the case much taller and square to accommodate it.

The new 5-Speed

Tremec wanted to kept all the great features of the TKO but package it up in much more streamlined case. They made the shift from a topload design to an end-load design. The end-load design, similar to the super strong Magnum 6-speed, is significantly stronger and allows the case to be much smaller. The three-piece aluminum housing provides outstanding structural stiffness and includes main case, intermediate plate and rear extension. Gaskets at all flanges simplify assembly and eliminate fluid leaks. Improvements just didn’t stop with the case. All new wider, stronger gear sets made with special grade ASTM 4615 steel improve gear design. Shifting is improved through use of multi-cone synchronizers carried over from the Magnum 6-speed, and hybrid synchronizer rings made of sintered bronze and carbon. NVH (noise, vibration and harshness) have all been improved.

All this means 600 lb.ft of torque capacity, and with the improved Magnum style syncro design means it can handle shifts at 7,500 RPM.

Check out all the specs and images below for more comparisons. Be sure to watch the TKX video at the end of the article.

More features of the TKX

• Equipped with a high-performance short-throw billet aluminum shifter that isolates road noise while providing clean, crisp shifts.
• Multiple shift locations for installation flexibility.
• Robust design with internal three-rail shift system and steel shift forks.
• Wide gear width increases gear life and torque capacity.
• 26-spline input shaft with a 31-spline output shaft for added strength.
• Built-in reverse light switch and cruise control safety switch.
• Separate GM and Ford case patterns and input configurations. Integrated GM and Ford transmission mount patterns.

Some similarities with the TKO

• Same length overall as the TKO. Can use any TKO crossmember and driveshaft.
• Bellhousing bolt patterns are the same. GM version and Ford version. GM TKO/TKX share the GM Muncie bolt pattern. Ford versions share the Ford Toploader transmission bolt pattern.
• Input shaft is 26-spline and bearing retainer design is the same. Can use any throwout bearing or hydraulic bearing for TKO or TKX.
• 31-spline output same for TKO/TKX.

TKX features and dimensions

Let’s look at some comparison shots of TKX and TKO