Miles Cook
August 1, 2002
Photos By: Mustang Monthly Archives

Since the first five-speed manual transmission appeared in the Fox-body Mustang in 1983, it's become the standard-bearer for gearboxes in late-model Mustang street cars. While the first '79-'82 cars had various forms of four-speeds, the norm now is clearly to have five forward gears with a generous Fifth-gear overdrive for effortless highway cruising. Even the vintage guys have gotten into the act as the typical T5 has become a virtual bolt-in for '65-'70 Mustangs.

But here (and this will be of interest to you vintage fans, too) we're going to concentrate on the various types of five-speeds that come factory-equipped in Fox and SN-95 Mustangs as well as the best options for a replacement gearbox.

First, a quick history lesson. Many of you have probably heard of two main companies that make the five-speed transmissions found as factory equipment in modern Mustangs or that are a popular replacement-Borg Warner and Tremec. The short version is that Borg Warner and Tremec are now the same company.

Here's how it happened: Borg Warner and Tremec made transmissions and other components for several decades. In 1995, DSA of America-a division of the huge corporation known as Dana-bought Tremec. In 1997, DSA also bought the manual transmission division of Borg Warner. In 1998, another company called Spicer S.A. DE C.V (located in Mexico) acquired Dana's manual transmission division (which included both Tremec and Borg Warner). The U.S. subsidiary of Spicer is now known as Transmission Technologies Corporation (or TTC) with facilities in Michigan and Ohio. So that's how it stands today.

What follows is a review of the current available five-speed transmissions for a street-driven late-model Mustang. The cars that the vast majority of you own have these units and if they're treated well, this article will be just an FYI for you. If you need to replace the five-speed in your car, you have some choices in terms of an upgrade and we'll touch on that, too. You can think of the five-speed transmission gamut for Fox and SN-95 Mustangs in three general ways. First, there are the legions of T5 variants used in all Mustangs from 1983 to 1995. Second, there's the T5's replacement known as the T45 (recently replaced by the TR-3650 in 2000), which came on the scene in 1996 with the introduction of the 4.6-liter modular V-8. And finally, there are the "Tremec" five-speeds, which, with one exception-the 351W-powered '95 Cobra R-are an aftermarket upgrade for late-model 5.0s. That's the basics, now let's look at the details.

Borg Warner (Now TTC) T5
The T5 has been the bread-and-butter for manual transmission Mustangs since 1983 and continues to be the best for the average street car when it's time for replacements. But there are about 40 different versions of the T5 and if you have an older car, this is a perfect chance to upgrade to a better T5 than what you might have now.

The T5 is a relatively lightweight (77 pounds) overdrive-equipped (Fifth gear) transmission that has been subjected to more hard use than it was ever intended to see. As such, it's gotten an undeserved reputation as not being strong enough for semi-powerful street cars. In truth, a T5, when treated well, will work fine behind engines making upwards of 400 horsepower; but only the best versions of the many T5s made over the years.

To clear up any confusion about the "World Class" nomenclature, all T5s installed in Mustangs in 1985 and after are considered "World Class" units. Borg Warner upgraded the T5 to "World Class" status by adding tapered roller-cluster bearings; caged needle bearings under First, Second, and Third gears; double synchros and First and Second gears; and friction material bonded to First through Fourth-gear blocker rings. However, these '85-'89 T5s with their 3.35 First gears were only rated with a 265 lb-ft torque capacity-so among all "World Class" T5s, some are better than others. If the T5 in your '89 or older Fox 5.0 needs to be replaced (or it can be rebuilt), you'll want to upgrade to the following stronger innards or a '90 or newer unit.

After numerous instances of breakage (mainly Third gear) on the '85-'89 units, Ford and Borg Warner made a number of improvements for 1990. These included a coarse-pitch Second and Third gearset (fewer yet stronger teeth) and specifying 4615 steel for Third gear and the cluster, and 4620 steel for Second gear. This increased the torque capacity rating to 300 lb-ft. If you're having an '85-'89 T5 rebuilt, you can install these stronger pieces available as a kit from D&D Performance.

The production T5 was improved again for the '93 Cobra by replacing the 15-needle bearings found in the input gear "pocket" with a tapered roller bearing, which reduced mainshaft deflection and improved gear-tooth contact. This Cobra-only T5 had an increased torque-capacity rating of 310 lb-ft. This setup was also used in '94-'95 Cobras, but not added to T5s used in regular '93-'95 GTs. And just so you know, all T5s use Dexron III ATF for lubrication.

What does all this mean to those who might need another transmission? Our recommendations are as follows: If you're going to have your existing transmission rebuilt, be sure you add the '90-and-newer type upgrade kit available from D&D Performance (PN AK1). If you're going to buy a used T5 from another car, we'd steer towards one from a '90 or newer 5.0, preferably with as little mileage as possible.

If you want to upgrade to a brand-new T5, the best bet would be to go with the FRPP aftermarket heavy-duty unit available from D&D, Ford Racing Performance Parts, or any other FRPP dealer such as Dallas Mustang. It carries PN M-7003-Z.

Tremec T45 And TR-3650
The 4.6-liter modular V-8 appeared in the '96, and along with it a new transmission known as the T45. Both GT and Cobra models use the T45, which has an integral clutch cover (bolts on from inside the housing). The T45 will not work with pushrod 5.0 (or 351W) engines due to its 4.6-specific bellhousing bolt pattern. While it has an impressive 375 lb-ft torque-capacity rating, in some circles it's known to have less-than-bulletproof internal shift components such as forks and Z-links. However, since its production began, improvements have been continuous. Like the T5, the T45 uses Dexron III ATF.

In the middle of 2000 production, a new transmission was introduced for the Mustang. Dubbed the TR-3650, it's a clean-slate design from the ground up, totally separate from the T45 it replaces. We spoke with the folks at D&D Performance and this unit is still so new that they don't have in-depth info on it yet, but will probably know more later this year. The best way to describe a TR-3650 at this point is that it's an amalgamation of the T45, the TR3550 and the T56 six-speed. Since the switch occurred midyear during the 2000 GT production run (recall there were no 2000 Cobras produced other than the Cobra R which was equipped with a T56) those who own a 2000 GT might have a car with a T45 or a TR-3650. It's easy to tell the difference: If your car's transmission has the drain plug on the bottom of the case, then it's a TR-3650. If it's on the side, then it's a T45.

If you've already hurt the T45 in your 4.6-powered SN-95, new ones are available from D&D Performance or you could have yours rebuilt. As for the TR-3650, they're not available from the aftermarket yet, but likely will be as soon as 2000-'02 Mustangs come off of warranty.

Tremec TR-3550/TKO
The Tremec TR-3550 is probably the most popular five-speed upgrade for those who need-or feel they need-something stronger still than the FRPP heavy-duty T5, also known as the "Z" trans. A spin-off of the Ford Top Loader four-speed, it has the same center-distance as the Top Loader. But it adds several goodies to the pie, with, of course, the overdriven Fifth gear being the biggest advantage. It also has an aluminum case, countershaft tapered roller bearings, caged needle bearings under First through Third gears, an internal shift rail, and a torque capacity rating of 350 lb-ft. In 1995, a revised 3550 came on the scene and it's known as the TKO. Its 360 lb-ft capacity rating is due to its larger input and output shaft sizes-the only difference between the two. The TR-3550 has a 10-spline input and a 28-spline output, while the TKO has a 26-spline input and a 31-spline output.

Although the TR-3550 is known to have a reputation for a notchier shift feel than a T5, it's usually minimized by proper break-in procedures, the right lubricant, and the use of an aftermarket shifter. Speaking of lubricant, the TR-3550's brass blocker rings, which require a 500-mile break-in period, necessitate the use of GM Synchromesh fluid and not Dexron III ATF, which would cause synchro failure. There are also other issues with the TR-3550 such as the requirement of a different bellhousing (the Tremec and T5 patterns are different) and an AOD crossmember in Fox-body cars since its rear mount is farther back than a T5. But if you decide to upgrade to one of these gearboxes, whomever you buy the trans from will be able to assist you with the required parts to ensure it's a bolt-in affair.

All Hail The Mighty T56
Although this is mainly a guide to five-speed transmissions for Mustangs, we'd be remiss to not touch on the T56 six-speed, which is now factory equipment in only the second-ever production (the first being the 2000 Cobra R) Mustang with a six-speed-the '03 supercharged SVT Cobra. The main drawbacks to a T56 are its weight (115 pounds) and the price (at least $2,700 to get one installed in a Mustang). It can be done, though, and two versions are available from D&D Performance. The aftermarket Ford unit is rated with a 440 lb-ft capacity and its bellhousing bolts up to a 5.0 or 351W small-block-D&D also offers one that works with 4.6 modular motors. For the last word in a bulletproof OEM-type transmission, look no further than the Dodge Viper-spec T56 that's rated to handle a whopping 550 lb-ft of torque. D&D Performance custom rebuilds brand new Viper T56s using unique D&D parts that, among other things, make them fit behind a 5.0 or 351W small-block. Clearly, this unit is more than enough for even the most radical street car. For the full scoop on all things T56, call D&D or visit the company's Web site.

Where Are These Transmissions Available?
Although many dealers offer T5 and Tremec transmissions, two popular sources for new units are Ford Racing Performance Parts and D&D Performance. To procure a used T5 (remember the '90 or newer ones are the best), Mustang Parts Specialties is a good source. The contact info for all three of these businesses is listed below. And check out all three company Web sites, too, as they provide a wealth of additional information.