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When it comes to piecing together the perfect drivetrain combination for your street rod, the engine is only one piece of the puzzle. Just as important as it is to decide what powerplant you want powering your weekend warrior, figuring out the perfect transmission to back it is just as crucial.
Luckily, the fine folks at TCI Automotive have come up with multiple transmission options for every street rod, including their stellar 6X Six-Speed automatic. According to the folks at TCI, their 6X has been rated to handle up to 850 horsepower. This transmission was the perfect candidate and we were confident that it would take anything that we dished at the ’36 Ford project featuring a 5.0L Coyote engine breathing under the hood. Check out the ins and outs of this fine piece of equipment below.
The Basics Of TCI’s 6X Six-Speed
According to TCI, “TCI’s base model 6X (Part # 271600) is designed for versatility and can be mounted behind most all Ford, Chevrolet, and Chrysler applications.” Add to that, TCI’s guarantee of the 6X handling higher horsepower demands of a street performer like this ’36 and it becomes the perfect marriage of safety, reliability, and ease. This makes it the ideal transmission for hot rodding and Pro-Touring alike, as well as with racing applications. Although we’re estimating around 500-600 hp out of our build, TCI can build the famed 6X to handle upwards of 1,300 hp if your ride warrants the need.
We were wanting to build a transmission that would have a reputation of taking the abuse and punishment that racers and street cruisers are known to dish out. –Will Vance, TCI Product Specialist
“The reason we did that is because that transmission has a reputation for being extremely reliable and being able to handle lots of horsepower, and that’s what we were looking for. We were wanting to build a transmission that would have a reputation of taking the abuse and punishment that racers and street cruisers are known to dish out.”
While your traditional 4L80E transmission usually features just four gears, the folks at TCI came up with a special valve body complete with a third shift solenoid. It works with TCI’s transmission control unit to give customers five regular gears and one overdrive gear. Matched with the required TCI EZ-TCU transmission controller and harness (Part # 302820) and fitted with optional components like the Outlaw 2-Button Shifter, this automatic transmission is one of the most customizable and functional for higher-horsepower, street-driven machines.
What Sets the 6X Apart From The 4L80E
So you probably want the juicy details on exactly why we chose the 6X as the transmission of choice for our ’36 Ford project, right? As we mentioned, while the 6X Six-Speed transmission is based on GM’s 4L80E transmission, it differs in many ways.
Most automatics only offer four gears, and if you’re lucky an overdrive. But with six forward gears, the TCI 6X transmission offers six close-ratio forward gears which ultimately optimize your vehicle’s performance past the capabilities of a traditional 4L80E keeping your engine in its peak power band. This not only means better acceleration times on the street, but also translates to better ETs on the track, or any other performance driving that we will throw at our Coyote-powered ’36 Ford.
The planetaries inside the 6X are also upgraded and are in-turn substantially stronger than those in an OEM-style transmission. Rather than using factory-style planetaries, TCI manufactures their own using in-house CNC machines and state-of-the-art equipment.
In doing so, TCI can create their internals to better withstand the harsh demands of high-horsepower applications. The gear stands are also much heftier and custom built from high-grade billet steel to ensure lasting performance and durability. In addition, Alto Red Eagle clutch packs also add to the transmission’s strength, equipping the 6X with the same clutch material found in TCI’s 2,500hp-rated ProX Turbo 400 drag racing transmissions.
Other components, like a heavy duty kickdown band, and a more robust overdrive fourth gear clutch feed only add to the 6X’s hardy reputation and thus, the reason it became our weapon of choice to back up our Summit Racing Coyote combo.
TCI 6X Specs
- Automatic valve body with special third shift solenoid
- Slip-on yoke
- Lockup
- Aluminum clutch hub
- Aluminum case
- Natural case finish
- Patented HDT Coating for cooler operating temperatures
- Six forward gears- 2.97, 2.23, 1.57, 1.18, 1.00 and 0.75
- Fully programmable automatic or manual shifting for improved acceleration and fuel economy at cruising speeds
- Self-contained, compact design eliminates clearance problems found with external bolt-on overdrives
- Compatible with all GM SBC, BBC and LS engines
- Compatible with many Chrysler, Ford and Pontiac engines
- For performance vehicles ranging from stock to 850hp, though custom units for upwards of 1300hp can be ordered
- EZ-TCU Transmission Controller, harness and 4-speed automatic shifter required for standard automatic operation as well as to take full advantage of the 6X’s performance capabilities
With a compact design, the TCI 6X Six-Speed can be utilized in even the most constrained spaces. The custom transmission crossmembers, plus the low profile on the frame of our ’36 give you a sense of the transmission’s non-envasive construction. Because of this self-contained design, the 6X eliminates clearance issues one might usually find with transmissions featuring external bolt-on overdrives (especially in tight areas like stuffing this beast under a ’36 Ford floor pan).
Because of the transmission’s hardy operating limits, it offers a unique driving experience–weather you’re planning to race your car down the strip, take it to some serious open-track events, or just carve those canyon roads like the pros, this transmission will not let you down, even with one hell of a potent engine powering your ride.
Certainly, not every high-performance ride will be driven on the street like our custom street rod will, but with the 6X being electronic and thus fully programmable, with options for both automatic or manual shifting, the modern Six-Speed gives us the ability to set the automatic transmission up for a variety of factors–from improved acceleration and better fuel economy at cruising speeds, to quicker shift responses and better track times. This also means that you can manipulate things like the shift points to crank up the performance and response of the 6X Six-Speed when things like fuel economy take a backseat to cutting down the tree at the drag strip.
“The special valve body is what makes the TCI 6X Six-Speed so spectacular”, TCI Product Engineer Bob Harrison told us. This is because TCI has added a third shift solenoid to the valve body in order to split the shifts between first and second gear, as well as between second and third.
This gives the transmission six full gears to take advantage of during a variety of driving situations. A new software package was created by TCI transmission specialists to take full advantage of this third solenoid setup, which is programmed right into the EZ-TCU to get optimal performance out of the 6X Six-Speed. With no laptop or special tuning software required, nor previous tuning experience needed, any automotive-minded individual can program the 6X for things like shift points, shift speed and shift firmness, as well as program the gearbox based on speed, RPM range, and load.
Two custom calibrations can even be stored in the EZ-TCU, which makes switching your transmission’s calibrations from your street setup to a designated track mode as simple as pushing a button.
Just like reliability and response are important aspects of any transmission, so too is the ability to keep it cool for better drivetrain efficiency. Every TCI transmission, including the 6X features a patented HDT Coating for improved cooling and lower operating temperatures, which is applied to the transmission case before each unit is shipped.
One final feature the 6X Six-Speed boasts is that each transmission goes through a rigorous and comprehensive testing process prior to being shipped. Just like with all TCI transmissions, the 6X is run across a computer-controlled transmission dyno and a hydraulic tester valve body dyno to ensure durability, guarantee proper line pressures, and confirm top-notch performance.
Left: The valve body installation is a delicate procedure, but the pros at TCI obviously have this down to a science. Right: Hydraulic testing of the internal circuits is done on each and every unit built to ensure both function and longevity.
This testing process is documented for each individual transmission that leaves TCI’s facility and can be found in the form of serialized spec sheets packaged with the transmission. With each transmission built from start to finish at TCI’s Mississippi facility, you can rest assured that each 6X Six-Speed is handled with the utmost care to provide your ride with the best quality high-performance transmission available today.
Once the final bolts are tightened this baby is ready to be run through TCI's rigorous testing process. Right: The final torquing of the pan bolts is a crucial step as both under tightening or over tightening can cause unwanted leaks and rail or seating damage to the unit.
Rounding Out the 6X Six-Speed
Here you get an up close and personal sneak peek of the installation of the overrun planetary.
Just as important as the transmission you choose for your high-performance ride is the torque converter you choose to run when installing an automatic gearbox. Choosing a torque converter that can handle the amount of power you’re planning to push through it is very important. For this ’36 Ford project, the idea was to take advantage of all aspects of the custom rod, from cruising around town and displaying on the show fields, to competing at track events. Because of this, the StreetFighter torque converter featuring a 3000-3,200 stall was chosen.
Top Left & Right: The component assembly and drum assembly requires quite a few pieces of the puzzle, but as you can see, it goes together quite nicely. Bottom Left: The installation of the front pump assembly. Bottom Right: The over-run drum and input shaft installed.
Each StreetFighter torque converter that is offered by TCI features furnace-brazed fins, hardened pre-ground pump hubs, and needle bearings. These converters are pressurized and leak tested prior to being shipped to guarantee all of the weld seams meet or beat TCI’s high standards, as well as computer balanced to reduce damaging drivetrain vibrations.
With everything assembly the over-run planetary and drum is inspected and installed.
Adding the StreetFighter converter to our 6X Six-Speed setup will give us even better low and mid-range power, improve reaction times, allow for higher RPM launches in the low to mid 3,000 range, and ultimately cut down elapsed times during track competitions. Of course, all of this translates just as well to the streets when looking for plenty of oomph to get up to speed or jam up those freeway on-ramps. StreetFighter torque converters can be used in a variety of applications, but the 3000-3,200 stall was chosen specifically to help get the best performance from the 5.0L Coyote and 6X Six-Speed setup. If you’re interested in the same setup that we went with you can look up more information using part number 242940. It is the 10-inch StreetFighter with Billet front and lock up clutch.
With TCI’s 6X Six-Speed, this ’36 Ford will be locked and loaded for the best performance in any situation we throw at it. When it came to getting the most out of this ’36 Ford destined to become a high performance street rod, we couldn’t think of a better way to go. Stay tuned as we dial in the custom touches to our Coyote and get some real numbers put down on the dyno!
Be sure to check out our exclusive gallery of the build process below!
