Junk Yard to New: Late Model Mustang Tremec Guide


You know it as well as I do—a stick transmission is the only way to go in a Mustang. In the Fox-body 5.0 days, opting for an automatic just killed performance, while ordering the 5-speed made the car a riot to drive. While technology has closed that gap in recent years, it’s still really no contest; the automatic is boring and slow, and the 5- (or 6-) speed is fast. The only exception, maybe, is if you’re building a 900 horsepower, drag-only car, in which case sometimes a built C4 or ‘glide may be the hot ticket. But for those of us with street cars, the 5-speed is the ticket. If you are inline for an upgrade, you have come to the right place, as we have enlisted the help of the folks from Tremec transmissions to bring you a guide to picking the right tranny.

Fox Body and SN-95 Transmission History

The Fox-body Mustang came onto the scene in 1979 but it was a wheezer until the return of the GT in 1982. In ’83 it got even better, with a Borg-Warner T-5 5-speed trans replacing the previous 4-speed overdrive. The T-5 was standard in all Mustangs from that point until the mid-’90s, at which point Tremec bought B-W’s transmission business and took it over. For the better, we say. Tremec continued to supply the T-5 for 6-cylinder Mustangs as well as a beefier T-45 for the V8 cars, before getting serious with both OE and aftermarket transmission offerings for the Mustang. But let’s back up and look at the earlier boxes, shall we?

This is the T-5, variations of which came in V8 Mustangs from 1983 until 1995.

Holding true to engineering and production line changes throughout a car’s life, not all Borg-Warner T-5s are the same. The main split in the early boxes is the difference between the World Class (WC) and non-World Class (NWC) transmissions. In ’83 and ’84, the Mustang had the basic T-5, or non-World Class, unit, which was rated at 265 lb-ft of torque capacity. In ’85 came the WC T-5 with a deeper 3.35:1 first gear (compared to 2.95:1 for the NWC) and better internals for smoother shifting. The torque rating stayed the same, though. There was also a T-5 used behind the turbocharged 4-cylinder cars, but ignore it—it won’t handle the power of even an average 5.0.

From 1990 to ’93, the WC gear set was made stronger with higher nickel content and slightly lowered second and third gear ratios. The torque rating jumped to 300 lb-ft. That gained another 10 lb-ft in the ’93 Cobra-spec T-5 that used a front tapered output bearing and steel front bearing retainer. That same year, Ford released a service unit (sold primarily through Ford Racing) that was even better; the Z-spec T-5. It had a 2.95 first gear, .63 overdrive, hardened gears, a short-throw shifter, a steel front bearing retainer, tapered output shaft bearing…basically all the good stuff was thrown in this transmission. Appropriately, the torque rating went up to 330 lb-ft, and was said to handle 450 horsepower (without slicks and a 5,000 rpm clutch drop anyway).

The 5.0-liter SN95 Mustangs of 1994 and ’95 were the last to see a T-5 in a V8 Mustang (though it was still used in the V6 cars until years later). In order to put the shifter in a comfortable place for the driver, Ford increased the bell housing depth and therefore the input shaft length. They also killed the neutral safety switch. The 3.8L V6 cars still used the T-5, with a .68:1 overdrive, but thanks to ever-increasing electronic controls on new cars, it was devoid of a mechanical speedometer drive. Otherwise, it was the same as the non-Cobra V8 trans.

Then Comes Tremec

Ford went to Tremec (stands for Transmission and Mechanical Equipment) to build a stout transmission for the limited-edition ’95 Cobra R, and they responded with the TR-3550 5-speed. Just a year or so later, Tremec took control of Borg-Warner’s transmission production and supplied the manual transmissions to the Mustang from then on.

With the debut of the modular motor in 1996, the transmission changed again and became the T-45. The bellhousing was now integral with the gearbox, and had a different bolt pattern so that it wouldn’t mate to a 5.0L. Not without a ton of work anyway. Internally it was very similar to the T-5, though nothing interchanges between them, and it was rated at 330 lb-ft. A common gripe about the T-45 is the reverse gear: though it was synchronized, many users complained that getting it into reverse was a gear-crashing exercise.

The 3650 as found in the modular-powered, S197 Mustangs

The Tremec that started it all, the 3550, circa ’95. 
The first transmission that Tremec built was for the Cobra R in 1995. A year later, Tremec would take over production of the Mustang’s transmission line up to the 2010 model year.

The T-45 had a relatively short run (’96 through mid-2001) until it was replaced by the Tremec-designed TR-3650. The 3650 initially came in ’01 Cobra and Bullitt Mustangs, before production was ramped up to meet the needs of all V8 Mustang production around January of ’01. Exceptions include the 2000 Cobra R and ’03-’04 Terminator Cobras, which were all equipped with the T-56 6-speed. The ’03-’04 Mach 1 also used the 3650, before some significant changes to the product occurred with the introduction of the S197 platform.

When the “New Edge” Mustang came out in 1999, the mod motor was still backed by the T-45, a straight carryover from the ’96-’98 cars. But when the Mustang was redesigned again for the ’05 model year, the T-45 was replaced with the 3650 that had been used in the prior, hotter Mustangs.

The internals were basically the same as the T-45, but thanks to Ford’s intense efforts to eliminate noise, vibration, and harshness (NVH), the shifter was moved off of the transmission, in what Tremec calls a semi-remote shifter. Immediately, racers and anyone who tried to bang shift the trans complained about missed shifts and overall sloppy shifting. Aftermarket shifters and fixes helped, but only a little.

Tremec And The Aftermarket

Up until the ’03 Cobra came along and forever changed the way the masses viewed Ford’s Modular engine, many enthusiasts were still busy trying to ring out the most they could from their Windsor-based combos. And as all Blue Oval faithful know, the capabilities of the stock T-5 had long been exceeded. Following the success of the TR-3550 in the ’95 Cobra R, Tremec made the unit available to the Mustang aftermarket; again touting it as an effective T-5 replacement with 350 lb-ft. of torque capacity.

The 3550 becomes the TKO

A series of revisions quickly followed, and in ’97 the 3550 was re-released as the 425 lb-ft TKO. Benefiting from upgraded input and output shafts, a bolstered main case, revised gearing, and upgraded materials, the TKO was a near instant success in Ford drag racing circles. Tremec quickly spread its influence into the road-racing arena as well, with the release of the TKO-II, which featured a 0.82 overdrive (3550 and TKO had a 0.68) for high-speed pulling power and 475 lb-ft. of torque capacity.

Tremec sells bellhousings that bolt the TKO-500/600 onto popular engine combinations, like small block Fords and Chevys.

The TKO raged on unchanged for several more years, until Tremec was all but forced to address the needs of Brand X (GM) customers around 2002. It seemed that word had gotten around on the street about the 5-speed brute that all the serious Fox-body guys were using, and they too liked the idea of a tough stick-shift with overdrive. The release of the TKO-500 and TKO-600 in 2004 was what followed. Offering multiple shift locations, dual speedo pickups (mechanical and electric), a variety of crossmember mounting configurations, and up to 600 lb-ft. of tire shredding torque capacity, no longer would the TKO be strictly the darling of the Ford world, but insanely popular in early GM and Mopar segments as well.

The main difference between the 500 and 600 is the gear ratio: The 500 uses a 3.27:1 first, while the 600 has a 2.87:1 ratio. The lower the ratio the bigger the gear, so with more surface area comes more strength and a higher torque rating. Also the 600 is only available with a 26-spline input shaft, whereas you can get a 10-spline input in the 500 (though 26-spline is also offered). The 10-spline input shaft is standard for all the Mustangs, but is weaker than the 26-spine, so the only reason you’d go with the 10-spline, in our opinion, is if you already have a 10-spline clutch.

Adding Another Gear with the T-56

The TKO would eventually go on to become the transmission of choice for nearly all serious road-going manually-shifted muscle cars, regardless of brand, selling over 60,000 copies to date. Meanwhile, as more race-bred technology found its way to the street and the advent of computer-controlled horsepower gave street performance enthusiasts an easy way to put it all to use, the Tremec T-56 gained momentum as an all around performance favorite thanks to the success it had realized in applications like the ’03-’04 Cobra (as well as the Viper, Corvette, and Camaro/Firebird).

(Left) The T-56 6-speed as found in the ’03-’04 Cobra. (Right) The rugged TKO II road-race transmission.

While perhaps less than desirable for hardcore drag racing due to its weight and virtually useless (on the dragstrip) fifth and sixth gears, the T-56 offered an exceptional balance of strength, smoothness, and practicality for many a high-horsepower street car. The only real problem was a lack of flexibility for early swaps with shifter locations that may work great for a Terminator Cobra, but not so well for a 4-valve Fairlane conversion, etc.

Tremec’s Hardcore T-56 Magnum

Here’s a pre-production image of the T-56 Magnum with bellhousing and crossmember for S197 (including 2011+) Mustangs, which are available from Tremec. Check out their website (Tremec.com) for shifters, overdrive gearsets, driveshaft yokes, and lots more.

The T-56 Magnum is Tremec’s first big foray back into the aftermarket. Since 2005, guys haven’t had a viable transmission for cars with big power, like high-horsepower blower and turbo cars.

So in 2009 Tremec answered the car crafters’ call with the debut of the T-56 Magnum 6-speed. Based on the latest and greatest O.E. technology, the Magnum was (and is) based on the TR-6060 family of transmissions that first made its appearance behind the supercharged 5.4 of the ’07 Shelby GT500. Conservatively rated for up to 700 lb-ft. of torque (up from 450 of the original T-56), the new Magnum offered the crisp shifts and refinement of a world class supercar, combined with all the flexible features of the utilitarian TKO. Designed heavily with the Fox and SN95 Mustang market in mind, the Magnum is an easy and worthwhile swap for any heavy-hitting Fox-based vehicle from 1979-2004.

The newest kid on the Tremec block is an extended-length version of the Magnum 6-speed specifically designed for 2005-up S197 Mustangs. Tremec’s Nate Tovey said, “This is Tremec’s first big foray back into the aftermarket. Since 2005, guys haven’t had a viable transmission for cars with big power, like high-horsepower blower and turbo cars.” The extended-length Magnum features a unique direct-shift extension housing that replaces the notoriously sloppy semi-remote units that have come from the factory since the launch of the S197 Mustang in 2005. This goes back to the significant changes we mentioned regarding the 3650 above, which were mainly centered around the new vehicle architecture.

The Upgrade Path For Your Mustang Generation

Aftermarket companies like D&D have T-56 retrofit kits for all '79+ Mustangs.

Fox Body (’79-’93)
• Factory Transmissions: T-5 Non World Class in ‘’83-’84, World Class from ’85-’93
• Best Replacement Junkyard Trans: Look for a T-5 from a ’90-’93 model, as they’re a little bit stronger, especially a Cobra World Class T-5
• New Tremec Offerings: TKO-500 and 600, T-56 Magnum
• Supporting Parts Needed: The TKO is a bolt-in but you’ll need a TKO-specific bellhousing, which is sold by many aftermarket companies. The stock crossmember is used. Also need a 31-spine driveshaft yoke (available from Tremec) Driveshaft length is stock. The T-56 Magnum will need a specific bellhousing as well, aftermarket driveshaft, 26 spline clutch kit and transmission cross member.

SN-95 (’94-’98)
• Factory Transmissions: T-5 ’94-’95 are the same, and T-45 ’96-’98 are too.
• Best Replacement Junkyard Trans: Just find the lowest-mileage one you can. ’94-95 and ’96-98 won’t interchange.
• New Tremec Offerings: TKO 500 and 600, T-56 Magnum
• Supporting Parts Needed: The TKO is a bit shorter than this model’s T-5, but many companies sell a small spacer that bolts to the back of the driveshaft to make up the difference. The mounting pad is a little higher too, which can be taken care of with some body washers or a similar spacer. The T-56 Magnum will need a specific bellhousing as well, aftermarket driveshaft, 26 spline clutch kit and transmission cross member.

 SN-95 ‘New Edge’ (’99-’04)
• Factory Transmissions: T-45 5-speed (1999-2000), 3650 5-speed (2001-2010), T-56 6-speed (2000 Cobra R)
• Best Replacement Junkyard Trans: Get the latest one you can, since Tremec experienced some minor issues with the early units. The T-45 and 3650 do not interchange without a costly driveshaft conversion. The GT500 6060 is also an available upgrade but requires a new driveshaft and 26 spline clutch disc.
• New Tremec Offerings: T56 Magnum
• Supporting Parts Needed: The T-56 Magnum will need a specific bellhousing as well, aftermarket driveshaft, 26 spline clutch kit and transmission cross member.

Tremec has a new T-56 Magnum kit designed for 2005-up Mustangs and come with a bellhousing and transmission crossmember, though an aftermarket driveshaft and clutch kit is needed. 2011+ Mustangs will need a speedo signal converter too.

S197 (’05-’10)
• Factory Transmissions: The 3650
• Best Replacement Junkyard Trans: The GT500 6060 is an available upgrade but requires a 26 spline clutch disc, new shifter, and crossmember. Stock 3650 driveshaft fits.
• New Tremec Offerings: T56 Magnum
• Supporting Parts Needed: The Magnum kit from Tremec (discussed above) comes with everything you need except a 26 spline disc and yoke-type driveshaft.

S197 5.0 (’11+)
• Factory Transmissions: Getrag MT-82
• Best Replacement Junkyard Trans: None
• New Tremec Offerings: T56 Magnum
• Supporting Parts Needed: The Magnum kit from Tremec comes with everything you need except a 26 spline clutch kit that must have the same stack up height as a 3650, yoke-type driveshaft, and speedo signal converter (converting 33 tooth hall effect to 12 tooth tone effect).

Aside from offering superior shift performance, other important features of the Magnum XL include:

• A slip yoke-style rear interface that eliminates the factory fixed-flange and allows users to run a one-piece driveshaft. This setup is not only stronger than the factory 2-piece arrangement, but reduces rotating mass by nearly 20 lbs. Additionally, an upgraded aluminum or carbon fiber driveshaft is a much less expensive proposition when using a 1-piece shaft.
• An SFI-certified steel bellhousing that is included with the transmission directly from Tremec.
• A swap-specific crossmember and mount that requires no modifications whatsoever to the vehicle, and maintains proper driveline angles.
• Six forward gears with two optional ratio sets (see notes below)
• Triple cone synchronizers on gears 1-4, double cone synchros for fifth, sixth, and reverse. (all use sintered bronze friction elements except 2nd gear, which uses carbon–not carbon fiber).
• Deep input shaft splines to accommodate dual and even triple disc clutches.
• A stout 700 lb-ft. of torque capacity.


Thank Ford's NVH engineers for this beauty. This is the factory semi-remote shifter and fixed flange output on the ’05-up 5-speeds. Sloppy shifting is guaranteed with this setup, but Tremec’s new extended-length Magnum 6-speed solves it.

Other Important Notes:

• Available gear ratios for the Magnum XL will be as follows:
• Part # TUET11430- 2.66, 1.78, 1.30, 1.00, 0.74, 0.50
• Part # TUET11940- 2.97, 2.10, 1.46, 1.00, 0.80, 0.63
• All Magnum series transmissions feature interchangeable fifth and sixth gears, allowing users to swap overdrive ratios or create their own combination. Both drive and driven gears must be replaced.
• The Magnum XL nomenclature is being introduced to eliminate the S197 Magnum title in lieu of trade name concerns, and because the new design will also eventually be applied to the late-model Camaro and Challenger markets.
• Performing a Magnum XL swap in a 2005-2010 Mustang requires no special modifications.
• Performing a Magnum XL swap in a 2011-up Mustang requires users to install an electronic speed calibrator into the factory harness to correct the speedometer. This part will eventually be available from Tremec, but will initially be sourced and sold by Tremec distributors.
• All Magnum XL swaps will require a 26-spline clutch disc and 1-piece driveshaft; not available from Tremec.
• All Magnum XL swaps will allow users to re-use their factory hydraulic throwout bearings. However, due to their shorter length, GT500 bearings will require a special spacer or shims.

Gear ratio chart - click the image for a larger version.

From Junk Yard to New, Tremec has it all

Tremec transmissions is a namesake amongst the Mustang community, and regardless if it is a T-5 out of your Fox body or a T-56 Magnum swap in a 2011 Mustang, there are many ways to improve the durability of your Mustang’s drivetrain.  There are many junk yard finds that serve as good upgrades, but nothing can top a brand new heavy duty Tremec transmission in your late-model muscle car.




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About the author

Rob Kinnan

Rob Kinnan requires very little introduction. Many would recognize Rob from his days as the Editor of Hot Rod Magazine. He is a dyed-in-the-wool hot rodder and muscle car enthusiast, a road racing aficionado behind the wheel of his Factory Five roadster, and a hardcore NASCAR fan.
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