Project Apex Shifts Into Sixth Gear With New Transmission Conversion

Since the birth of the automobile, manufacturers have been trying to make cars less user-involved and more reliant on the latest technology. In recent years, this has spawned a new era of vehicles that could be considered the digital revolution. The majority of these vehicles leave behind the manual transmission in favor of super-fast shifting automatic transmissions with computer-controlled gear operations. While these advancements in technology are favorable to certain motorsports, in road racing a manual transmission gives the driver the interface to control the car’s RPM throughout the course.

Project Apex is our 2001 Cobra and one of the last few years of the analog era. The majority of the driver’s aids on our Cobra are aimed at safety, rather than performance. Since automatic transmissions of this time were more adept at robbing power than providing the proper powerband, it would come as no shock that it was equipped with a manual transmission from the factory. That same manual transmission was extremely tired, though, and after we inspected the rest of the chassis we knew our options were to rebuild or replace.


This 135-pound TREMEC Magnum transmission has the ability to hold 700 lb-ft of torque. That is nearly 300 lb-ft more than the original TR-3650 transmission that came in our 2001 Cobra.

R&R Does Not Stand For Rest And Relaxation

Project Apex was essentially a roller when we purchased it. The engine had long since given up the ghost and the transmission wasn’t far behind it. Since we wanted to keep this chassis Modular-powered, we decided to rebuild the engine. An easy decision based on cost and product availability.

Our Cobra came with its original TR-3650 that had clocked nearly 215,000 miles. Upon our inspection, we quickly found that the input shaft had slop and a rebuild was required to make it trackworthy. However, even being rebuilt with the best parts would be a gamble of keeping it together. Each track day costs roughly $1,500 between registration, race fuel, tow vehicle fuel, and hotel, so our ideas of risking it with the TR-3650 began to dwindle.

It was at this point that we had to make the critical decision: build our TR-3650 to handle this kind of abuse, or upgrade to a transmission that would handle it out of the box. We knew we would have to, at the very least, swap out the input shaft for a hardened 26-spline unit and change out the shift forks and synchros to make our current transmission have a chance at lasting. The debate quickly came to a rest when we factored in the cost difference between the two options. The TR-3650 would require a complete overhaul, including replacing the flywheel and clutch. For only a few hundred dollars more we were able to give Project Apex a TREMEC Magnum.

Project Apex Gets Magnum Sized Load Rating

The chance to gain an extra overdrive gear and an additional 300 lb-ft of torque-holding capacity meant the new TREMEC unit was an easy choice. However, there were going to be several decision-making steps in the process. Things like gear ratio options, clutch selection, and driveshaft options had to be considered. Seeing as how we wanted it to handle long-term abuse, high-RPM shifts, and remain at a price-point close to the previous TR-3650, we had our work cut out for us.

We were familiar with the transmission’s ability to hold power, as we had used a Magnum on Project F-Word. Unlike the lighter Cobra, Project F-Word’s Magnum was mounted behind a Ford Performance Aluminator and situated inside a much heavier chassis. Nonetheless, the TREMEC unit has held up great and still provides Ivan with quick and smooth engagement in his truck, even when competing in autocross events.


The TREMEC Magnum was outfitted with Silver Sport Transmission products including the cross member that keeps the transmission at the correct level in the Project Apex chassis.

What we wanted was a close-ratio transmission that was designed to handle shifting up and down at high RPM. The ability to both hold massive amounts of torque and have synchros to aid in heel-toe shifting was going to be a major added bonus. Thankfully, the 135-pound unit contained a 26-spline input shaft, 4616-alloy chromoly gears and shaft, one-piece counter shaft, and triple-cone synchros, ensuring it was built to handle anything our 4-valve engine could throw at it. The Magnum six-speed with a 2.66 first gear was essentially aimed at road racers and made our final decision an easy one.

Project Apex Gets A New Clutch And Install Kit

Now that we had our transmission selected, we switched gears and started trying to determine which clutch and transmission installation kit would afford us the easiest route. With the key word there being “kit”, we decided to seek out expert advice from the knowledgeable folks at Silver Sport Transmissions, instead of trying to piece things together ourselves based on sketchy forum posts.

Fitment was paramount, as the last thing we wanted to do was work on the Cobra’s most difficult area twice. Silver Sport offers everything you need to get a modern transmission into a classic vehicle. However, our Cobra falls into the middle-child year range…not quite old enough to be a classic, and far too old to easily fit a modern transmission. This is exactly where Silver Sport shines.

Fitment and Function

To ensure proper fitment and driveshaft angle, Silver Sport’s crossmember connects our new Magnum into the chassis with no questions asked. While a crossmember is a simple bolt-on product, it’s a key element to the swap that can’t be overlooked. We also scored a slick Silver Sport shift handle and shift knob that adds a touch of class to our race car. 


There are always those products that give off a touch of class. In our case it was the Silver Sport Transmissions shifter and shift knob that gave the interior of Project Apex a nod.

Silver Sport also offers a hydraulic conversion kit, affording yet another modern amenity to our Cobra. . This kit removes our archaic clutch cable system, that is prone to stretching and inconsistent pedal feel, and replaces it with a hydraulically actuated throw out bearing. The newly-purchased hydraulic kit includes everything needed for the conversion and was extremely easy to install, sincewe paid attention to their instructions. 

Jeff Kauffman, Vice President of Sales and Marketing at Silver Sport, informed us that “the stroke of the master-cylinder piston assembly has to be at the right angle, with the right amount of travel, and clutch pedal travel also has to be just right, as well. There’s a lot that goes into getting it right.” This precise engineering would allow us to run at the track without any binding clutch issues or other problematic shift points.

Since the Silver Sport kit allows us to retain our stock clutch pedal, we only needed to mount the pedal to a custom firewall slave cylinder adapter. Precise height adjustment on the pedal keeps the pedal feel in the right spot, allowing us to shift gears at a rapid pace. This would conclude our hydraulic system upgrade.

We decided to do away with our clutch cable system and integrate a modern hydraulic setup. This will eliminate inconsistent pedal feel from cable stretch or even breaking.

One major concern was getting the pedal ratio correct, since our left foot would be visiting the clutch pedal frequently on track. Silver Sport took the guesswork out of it with their adjustable unit and instructions on properly setting it up.

When consulting with Silver Sport about a proper clutch for our application, Sales Director Brian Gwin suggested we run the McLeod RXT. We briefly questioned his judgment of using a high-horsepower capable twin-disc instead of something more aligned with the Project Apex power output, but were quickly informed of why this decision makes sense. 

“We suggest the RXT mainly because of the environment the car is going to be put in, not necessarily based on the horsepower output of the engine,” Gwin explained. “It has the light pedal feel, smooth engagement, and has horsepower capabilities of up to 1,000 horsepower. Furthermore, it can handle shifts well over 8,000 rpm.”

To pair the flagship McLeod clutch with a proper flywheel, Gwin suggested we add a McLeod aluminum flywheel to our invoice. “An aluminum flywheel is going to reduce the rotating mass of the assembly, which will allow the car to perform better in a road course and autocross environment,” Gwin informs. “This reduction in rotating mass will help with getting deeper into the braking zones and help with corner exit speeds.”

We paired a McLeod aluminum flywheel with a twin-disk RXT clutch. While our goal wasn't to hold 1,000 horsepower, the RXT made the most sense for our application, including shifting Project Apex at 8,000 rpm!

Lightening Up The Shaft

There is usually a fine line between strength and weight savings. However, when we visited  QA1 at the 2021 SEMA show, we saw that QA1 had teamed up with the aerospace industry to try and blur that line. Needless to say, we were eager to check out their new carbon-fiber driveshaft. Not only will this new unit save rotational weight in the process, but will also maximize the efficiency of our naturally aspirated engine by removing the amount of weight it has to push.


We tried to eliminate as much rotational weight as possible. To make it easier on our engine, we went with a QA1 carbon-fiber driveshaft.

Controlling Project Apex

Aside from steering and throttle/brake input, one of the main connections a driver has to their car is the transmission. This is why we decided to get a transmission that is known in the road racing community to not only provide crisp shifts and strong engagement, but is also smooth enough to allow us to heel-toe shift going into the corners. . Project Apex is not a cafe cruiser, nor a car show-stopper. We’re building this Cobra for on-track prowess.

Aside from adding strength, we also wanted to reduce the amount of mass our naturally aspirated 4-valve engine has to move in the process. This is why we sought out the lightweight flywheel and driveshaft. With a host of incredibly capable powertrain components installed, we are excited to hit the track and see  everything working together with both chassis and driver. Check out Ivan’s fastest lap at Barber Motorsports Park. 

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About the author

James Elkins

Born into a household of motorsport lovers, James learned that wrenching takes priority over broken skin and damaged nerves. Passions include fixing previous owners’ mistakes, writing, and driving.
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