Jim Smart
July 30, 2014

Classic Mustang five-speed conversions are nothing new, but how we do them is getting better all the time. There are piecemeal conversion kits and there are user-friendly conversion kits that make getting into five-speed overdrive technology an easy weekend task, getting you back on the road by Monday morning. Modern Driveline offers you a complete one-stop Tremec five-speed conversion package (T5 or TKO) for the '71-'73 small-block or big-block Mustang or Cougar complete with all hardware, crossmember, bellhousing, clutch and flywheel, related components, and transmission. It has everything you need and eliminates the stuff you don't need. What's more, Modern Driveline allows you to order “a la carte” meaning if you already have the part, you won't need it for your conversion.

If you're driving a '71-'73 Mustang or Cougar with a three- or four-speed stick, or even an FMX, C4, or C6, your first order of business is rear axle gearing. If your Mustang or Cougar has a 2.79:1, 3.00:1, or 3.25:1 axle ratio, cruise performance won't be what it could be with 3.50:1, 3.73:1, or 3.91:1 cogs. With 3.50:1 gearing, you can expect 2,000 rpm at 70 mph on average depending on tire diameter.

This is your basic T5 conversion kit from Modern Driveline for ’71-’73 Mustangs and Cougar. Some items are not pictured here but you get the idea. Modern Driveline can custom-tailor your five-speed conversion package for your individual application and provide what you need and not burden you with what you don’t need. This T5 package is for classic Mustangs with the original equalizer bar clutch linkage and bellhousing. The adaptor plate enables you to bolt the T5 to your Mustang’s original bellhousing.

We're working with the Rebuilding Generations Mustang convertible project car, which is a solid commitment to young and old working together in an effort to pass the torch to a new generation of car enthusiasts. We older folks can impart valuable information to young people while learning something new from fresh eyes who can spot the need for improvement perhaps showing us a better way. Rebuilding Generations is a program founded by Kevin Keep that was brought about by the guys at My Deals, LLC to help bridge the gap between the younger and older generations. The program's goal is to provide opportunities that will help build a mutual level of respect and appreciation of the knowledge and wisdom both generations have to offer each other.

The first Rebuilding Generations project is a '71 Mustang Convertible provided by Ryan Hoffins, marketing manager at Optima Batteries. On its website at www.rebuildinggenerations.com, you can see videos, photos, and interviews on the progression of this Mustang throughout the restoration process. This car was rolled out for the first time at the 2013 SEMA Show in Las Vegas.

01. This is the time proven Tremec World Class T5 five-speed transmission new from Modern Driveline with 2.95:1 First Gear and 0.63 overdrive. Because Modern Driveline is a Tremec Elite Dealer, you’re getting a new T5 right from Tremec’s production line. And when your T5 needs service, Modern Driveline can help with trained professional tech support and service. Each T5 is thoroughly inspected prior to shipment.

02. Modern Driveline offers a nice line of cast aluminum and QuickTime formed steel bellhousings for a wide variety of Ford applications.

03. Bruce Couture of Modern Driveline stresses the use of pilot bearings instead of bushings for smooth operation and durability. Though more expensive, pilot bearings are money well spent for longevity and smooth shifts.

04. The T5 and cable style bellhousing call for this aluminum engine/bell separator plate, which is a Ford part available from Modern Driveline.

05. Bruce Couture of Modern Driveline explains the fundamentals of clutch design and installation to Rebuild Generations, which is building the ’71 Mustang convertible in this article. Our subject vehicle is a 302ci small-block ride ready for the T5’s great efficiency. The car has been fitted with a Strange 9-inch rearend with 3.55:1 Traction Lok, which makes it ideal for the Tremec’s 0.62:1 overdrive.

06. Because we’re running a 302 V-8, Bruce has chosen a steel flywheel with a 28-ounce offset balance for our Superior diaphragm-style clutch.

07. Flywheel bolts on small-block Fords thread through the crank flange and right into the crankcase. Use Teflon sealer on bolt threads and keep oil inside where it belongs.

08. Flywheel bolts are torqued crisscross in one-third values to a total of 80 lb-ft.

09. This is something Bruce does on all of his clutch and flywheel installations. He checks the bellhousing to ensure it is perfectly centered on the crankshaft. Not all bellhousings are drilled perfectly, which can cause unacceptable side loads on transmission input shafts.

10. We’re installing a Superior diaphragm clutch from Modern Driveline. Superior Clutches handcrafts each clutch one at a time for Modern Driveline. If you opt for a Kevlar clutch disc, be confident in knowing Superior’s are 100-percent Kevlar and can withstand a lot of abuse. We’re installing an organic clutch disc for what will basically be a weekend cruiser. Pressure plate contact surface is cleaned with a high-evap’ solvent and a tack rag.

11. The Superior organic clutch disc is installed using the alignment tool provided. Loctite is used on Grade 8 pressure plate bolts, which are torqued in a crisscross pattern in one-third values to 35 lb-ft.

12. Bruce Couture offers a couple of suggestions for clutch alignment tools. Shown here are two plastic clutch alignment tools. One fine tooth and the other coarse tooth for different input shaft types. Bruce has taken a used up input shaft and cut it for use as a clutch alignment tool. He tells us the steel shaft works best if you can find one.

13. Because we’re going with a cable clutch conversion kit from Modern Driveline, we’ve opted for a cable-style bell and fork. Pivot ball has been lubed and the release bearing is lined up for transmission installation. Release bearing needs molybdenum grease around the inside, however, never use too much. Just a thin film of grease on these parts because you don’t want the excess caught up between pressure plate, disc, and flywheel.

14. Bellhousing is torqued tight using a 5⁄8-inch socket and extension.

15. This is how your Tremec T5 from Modern Driveline will arrive. Each T5 is thoroughly inspected prior to shipment to ensure integrity.

16. Our Tremec T-5 is secured on a transmission jack and is ready for installation. The T5 is light enough to install on your back underneath the car though this is not recommended. We have the good fortune of Modern Driveline’s lift and transmission jack along with Bruce’s experience.

17. T5 is raised into position and carefully splined into the Superior clutch disc.

18. Transmission-to-bellhousing bolts are torqued using a 5⁄8-inch socket and extension. This is best accomplished with the transmission tailshaft low for easy access.

19. Modern Driveline T5 crossmember is carefully fitted in place but kept loose during installation.

20. The T5’s internal shifter positioning is perfect for the Mustang and Cougar; it clears without a hitch. You may use nearly any kind of shifter boot and handle desired including Hurst and stock. You may also opt for a variety of aftermarket shifters from Modern Driveline.

21. Bolt heads should be pointed toward the front of the vehicle. Use flat washers and locknuts for transmission crossmember bolts.

22. Modern Driveline stocks and can order a DynoTech driveshaft for your application in steel or aluminum. We’re going with an aluminum shaft sized for the 9-inch Ford with a T5 transmission, which yields 1 inch of yoke showing with the vehicle resting on its tires with the suspension at rest. When you are seating the rear universal joint in the yoke, never over-tighten. Over-tightening will damage needle bearings in the caps. Get the caps seated and snug the U-bolts tight. Always use Grade 8 locknuts.

23. Completed T5 installation is clean and simple clearing the tunnel by a wide margin. No special fabrication or modifications are required. Any factory speedometer cable will fit this application.

24. Backup light switch is located in the left hand side of the transmission’s main case. All you gave to do is tie this plug into your Mustang’s factory backup light leads and you are good to go.

25. We’ve chosen to go with a Modern Driveline cable clutch release system, which is another installation article entirely. This is how it connects to the bell, looped 180-degrees around to the bellhousing.

26. We see a lot of cable clutch conversions void of this dust cover, which keeps dust and road debris out. It is a Ford part available from Modern Driveline.


TKO To Go

If you're running a lot of power, consider the Tremec TKO series five-speed transmissions for your conversion. The Tremec TKO500 has a 10-spline input shaft with a 31-spline output with 3.27:1 First Gear and 0.68:1 overdrive. The TKO600 has a 26-spline input shaft and 31-spline output with 2.87:1 First Gear and 0.64:1 overdrive. And finally there's the TKO600RR road race box with 26-spline input and 31-spline output with 2.87:1 first gear and 0.82:1 overdrive. If you're not certain which TKO to order, call or email Modern Driveline and talk with a tech rep that can help you make the right decision.