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Tech Alley               "Where you find all the answers."

Crazy Like A Fox Six-Speed

Modern Driveline brings your 1979-93 Mustang into the 21st Century with crispy T-56 Magnum smoothness and performance.

When Ford added a five-speed to the Mustang’s transmission line-up in 1983, it seemed way out there for those of us old enough to remember when even four-speeds were a fresh mainstream idea from Detroit. In time, five-speeds became the norm that is until Detroit decided we needed one more speed to think about and shift into.


TREMEC T-56 Magnum in a Fox Mustang

Enter the six-speed manual transmission as an enhancement to hot Fox body 5.0L Mustang performance. Although the first factory six-speed first arrived in the all-new 2005 Mustang, we were inclined to ask why a six-speed wasn’t possible in a Fox body Mustang for those of us who like the nimble, sure footed Fox. This was when our engineering department decided to investigate how to get six-speed performance into a 1979-93 Mustang. It wound up being easier than we ever imagined.

Modern Driveline introduces a complete bolt-in TREMEC T-56 Magnum XL performance conversion package for the 1979-93 Mustang. What’s more, you can perform this conversion in a weekend and be back on the road Monday.

Five-speed shifting has been a Mustang staple since 1983. The TREMEC T5 has served us all very well in more than 20 years of continuous availability and service. However, TREMEC’s new T-56 Magnum six-speed will help you forget all about that T5 box when you discover the thrill of the T-56’s gearing, easy shifting, and the benefit of two overdrive ranges for the open road.

Get Into Overdrive x 2

The T-56 Magnum is a revolutionary new six-speed transmission that combines the rugged demeanor of the TREMEC TKO five-speed and OEM TR-6060 (Corvette and Viper) to create the smoothest shifting six-speed transmission in the industry. You get OEM durability and aftermarket toughest in a single six-speed box. We’re talking crisp shifts, no missed gears, beefiness, heavy-duty bearings and synchronizers, and greater torque capacity for your Fox 5.0L Mustang.

What makes the TREMEC T-56 Magnum from Modern Driveline a great investment? Here’s the beef…

  • Beef:  The T-56 Magnum goes the original T-56 one better because it is a completely new six-speed transmission with a redesigned heavy-duty main case.

  • Gearing:  Modern Driveline’s all-new T-56 Magnum has an incredible 700 ft/lb torque capacity with gears similar to those found in the TR-6060 used in the Chevrolet Corvette and Dodge Viper. These gears sport a great face width plus two-piece laser beam welded construction. Two-piece units allow for much greater control over tooth angles, pitch, alignment, and more. This eliminates the chance of an over-thrown shift.

  • Countershaft:  Radically bolstered one-piece countershaft, which resists distortion. What’s more, it sports larger bearings in critical support areas for greater stability than ever before.

  • Input Shaft:  New and improved input shaft provides significant strength as the T-56 Magnum’s first line of defense against failure. You get a thicker 26-spline shaft with longer splines to accommodate today’s twin-disc clutches not to mention more material throughout. TREMEC also give you a larger input shaft bearing for greater support in front. Ford 10-spline shafts will not be available.

  • Synchronizers:  Because the Magnum has wider gears it also gets new high-tech synchronizers with cutting edge technology. These guys are considerably narrower than the old T-56 synchronizers featuring fine pitch tooth angles to effectively decrease the amount of travel necessary for proper engagement.  Spring-loaded ball-type inserts reduce friction, which reduces shift effort.

  • Shift Forks:  You couldn’t imagine a redesigned T-56 without redesigned shift forks featuring shift keys to virtually eliminate the chance of bent shift forks. This keeps shift forks on course without any chance of deflection and failure.

  • Retainers: When TREMEC completely redesigned the T-56 it took a close look at retainers and fasteners. Instead of the time worn snap ring, TREMEC went to a new split ring retainer design that will handle greater thrust loads and allow for tighter tolerances.

  • Main Case:  Though the T-56 Magnum looks similar to the old T-56, it is not the same transmission case by any stretch of the imagination. There’s more beef in this case not to mention changes in dimension that make it a far better case.  It can handle greater loads than the original T-56.

Real Beef — And Lifetime Tech Support

Modern Driveline is well known in the industry for unlimited lifetime tech support, and that’s what you get when you do business here. When you buy the T-56 Magnum six-speed conversion package for your 1979-93 Mustang, here’s what you get:

  • TREMEC T-56 Magnum Six-Speed Transmission
  • QuickTime Bellhousing for 5.0L Engine with separator plate
  • Clutch Fork & Release Bearing
  • Superior Multi-Friction Kevlar/Organic Clutch & Pressure Plate
  • Pilot Bearing
  • Modern Driveline Steel Flywheel (28 or 50 ounce offset)
  • All Hardware
  • All Appropriate Wiring Harnesses
  • Four Quarts of Synthetic Transmission Fluid
  • Steel/Urethane Crossmember & Mount
  • Clutch Alignment Tool

The TREMEC T-56 Magnum conversion package for the Fox Mustang is an easy weekend install because Modern Driveline has thought of all it for you. This installation has been executed and photographed to show you how easy the installation is and what it will mean for your Fox Mustang driving experience.


Shifter ball, boot, and handle are removed first.

Speedometer cable is disconnected next using a 7/16-inch socket or box end wrench.

H-pipe and catalytic converters are removed next. Original exhaust systems will have four cats. Most replacement systems will have two. O2 sensors and Thermactor Emissions tube must be disconnected.

Driveshaft is disconnected at aft axle flange as shown.

With transmission crossmember and mount removed and transmission properly supported, transmission is disconnected at the bellhousing. We do this for easier access to the bellhousing to engine bolts and clutch cable.

With transmission safely supported by a hydraulic jack, removal comes from pulling the T5 aft and away from the bellhousing.

This is the factory T5 bellhousing with clutch fork and cable still connected.

Two-bolt starter is removed next using a 9/16-inch box end wrench.

A 5/8-inch deep well socket gets the bellhousing to engine bolts, which frees the bellhousing. Clutch cable is also disconnected at this time.

Clutch is removed at this time using a 1/2-inch socket.

Because we have a healthy flywheel, we’re going to remove and resurface clutch contact surfaces for good adhesion. Clutch pilot bearing looks good.

Factory aluminum separator plate is removed at this time and will be replaced with a QuickTime steel plate compatible with the QuickTime bell and T-56 Magnum.

This is the time to replace the rear main seal if there is leakage. Most bellhousing leakage issues are transmission input shaft seals, not necessarily rear main seals.

QuickTime separator plate is installed next.

Flywheel face can be resurfaced by a machine shop or quick scuffed like this with a fine abrasive wheel.

Flywheel is installed next using a good thread locker/sealer on new bolt threads. Never reuse old bolts. Remember, these bolts go directly into the crankcase, which means they will leak if you don’t seal the bolt threads.

Flywheel bolts are torqued in one-third values in crisscross fashion to 75-85 ft/lbs. Snug first, then torque in thirds.

Whether you’re installing a new clutch or reinstalling the existing clutch, pressure plate surfaces must be hospital clean using brake cleaner repeatedly until the rag is clean.

A fresh Superior multi-friction clutch disc is centered with an alignment tool, then, pressure plate is installed with bolts torqued down slowly in one-third values using a thread locker on bolt threads.

Pressure plate bolts are torqued in one-third values to 35 ft/lbs in crisscross fashion.

QuickTime bellhousing from Modern Driveline is SFI certified and easy to install using a 5/8-inch deep well socket.

Modern Driveline clutch kits come with a clutch alignment tool for your convenience. However, for an even more precise alignment, opt for an old transmission input shaft, which is even more accurate in terms of alignment.

The TREMEC T-56 Magnum carries the clutch fork as shown, which fits right into the QuickTime bellhousing. Installation is easy.


From the left hand side, clutch fork and bell relationship looks like this. You can go with a cable or hydraulic clutch with internal or external slave.

The TREMEC T-56 Magnum fits comfortably in the 1979-04 Fox body’s transmission tunnel.

Modern Driveline’s tubular T-56 Magnum crossmember slips easily into place as shown.

With input shaft splined into the Superior clutch disc, QuickTime bell bolt-up is easy.

Modern Driveline’s aluminum driveshaft from Dynatech is a perfect fit, with ¾-inch of slip yoke showing with the aft pinion flange connected and wheels on the ground.

Stock clutch cable installs as shown and is easy to adjust.

Any modifications to the transmission tunnel are minor in scope with some of the overlap cut out or hammered flush.

The T-56 Magnum’s backup light duplex plug is different than the 1979-04 Mustang’s female connector. You will have to go with the Magnum’s male duplex counterpart, which is available from Modern Driveline.

The 1979-93 Mustang’s mechanical speedometer drive splines in as shown without special modifications.

Like the speedometer driven gear, the Motorcraft or Nippondenso starter bolts right into the QuickTime bellhousing. Access can get very tight especially if you have a road race pan.

The T-56 Magnum’s shifter sits exactly where it is supposed to with adequate clearance.

If you think your T5 or TKO feels good, wait until you get the T-56 Magnum’s shifter in your hand. Nice tight crisp shifts without a missed shift.

Enthusiasts Who Are Also Engineers

This is why you do business with Modern Driveline. We are not a large company with huge product development teams with bean counters and Wall Street investors looking over our shoulders. We are automotive enthusiasts bent on getting our products right before they’re ever sold to the public. We are also very determined to deliver great technical support after the sale. As a Modern Driveline customer, you will never be our guinea pig. We find problems before they get to you and solve them before they ever become a headache for you.

We don’t just find the fault — we find the fix at the prototype phase before products ever reach the mass production phase. And if you ever encounter a problem with any of our products, we invite your contact so we may solve it before it ever becomes a frustration for you. If there is a problem after the sale, we are here to provide lifetime technical support for any Modern Driveline product you buy.

If you're looking to upgrade your Mustang send us your details and we'll get back to you with a quote.  Or call...