The Mustang's T-45 Transmission

The Mustang's T-45 Transmission

Last Updated August 4, 2019 | Meghan Drummond

The T5 transmission was around for well over a decade before Ford introduced a new transmission to accompany the overhead cam style engines they’d begun to equip their Mustang GTs and Cobras with: The T45 transmission.

Though the T45 is frequently forgotten, it has some features that make it more desirable than an older T5. Similarly, though it was replaced by the TR3650 in short order, the T45 heralded in several important firsts for Mustangs.

T-45 General Information

The T45 was truly the middle child of Ford transmissions, and despite its more impressive achievements, it had some awkward growing pains. There were a few contributing factors to these problems that help to shed some light on the very short reign of the T45.

The T45 was the first manual transmission for the Mustang that was designed to work with the OHC style of the new engine. The next generation of transmission, the TR3650, would last from 2001 to 2010, and the T-5 lasted from 1982-1996. Compared to their decade long lifespan, theT45 seems incredibly short-lived at a mere five. Unlike almost every other transmission, the T-45 is entirely contained within one generation of Mustang.

Another contributing factor to some of the T45’s issues was that it was being produced in the middle of a major transition within Ford. Tremec took over production of Ford’s manual transmissions from BorgWarner starting with the T45. This means that some of the T45’s OEM parts are made by one company while others are manufactured by the other. There are people who will swear that there’s a difference between the quality of the transmissions manufactured by Tremec vs the ones manufactured by BorgWarner. For once, this is an argument not totally based on brand loyalty.

Mustang with black leather interior
1999 Cobras came with a T45 Transmission

Most people will tell you that the first year of production of anything is when they figure out the little fixes that make a product go from good to great. Unfortunately for the T45, it didn’t get that buffer period, and it took a while for Tremec to find the small flaws that needed to be fixed. By the time they’d found and addressed some of the issues, they had a new transmission to launch.

Because of these minor fixes, what year of transmission you buy matters more than who manufactured it, but since almost all later production was Tremec exclusive, it’s not inaccurate to state that the Tremec T45s tend to be better, it was just more a product of time than of one transmission company being particularly adept.

Year to Year Changes

Between 1996 and 1998, T-45 transmissions from Mustang GTs used a seven-tooth speedometer gear, though Cobras used an eight tooth speedometer gear. In 1999, both the Cobra and GT T45 were moved over to an electronic sensor speedometer.

In 1998, the 3-4 shift fork was improved. Unfortunately, the 1996 and 1997 Mustang have a weaker 3/4 shift fork. This is a common upgrade for the older versions of this transmission, and though it’s time-consuming it’s worth it for the piece of mind of knowing that you won’t suddenly find yourself desperately looking for third or fourth gear.

four silver metallic claws
The T-45’s Shift Forks

Specifications

Though the T-45 transmission is often overlooked, it does actually have considerable improvements over the T-5. By using a double-cone synchronizer design, less shift effort was required for the first and second gears. A strut-type synchronizer design improved durability, and it featured the first fully synchronized reverse gear in a Mustang transmission.

1999 Mustang Transmission Specs
TransmissionFirst GearSecond GearThird GearFourth GearFifth GearReverseTorque Capacity
T-45 3.37 1.99 1.33 1.00 .67 3.22 375 lb-ft

Modifications for the T-45

There are ways to improve your T-45 transmission if you’re invested in maintaining the T45 rather than replacing it. Most of the best ways to modify the transmission involve addressing the weaknesses that were present at manufacture. For example, the input shaft is known to be overly fragile, so upgrading to a 31-spline slip yoke can improve the durability of your transmission. If you have an early T-45 transmission, then eventually you’ll also want to upgrade the 3-4 shift fork since they’re known to wear out early.

Some of the issues with upgrading a T45 revolve around how little aftermarket support there is for it, especially in comparison to the T5 and TR3650. For many parts, T5 replacements will work. For example, a lot of people when looking to upgrade their shifter go for a TR3650 one, but the T5 shifter will be a better fit. Forums are fortunately full of people sharing their experiences with trying out different parts.

These modifications can quickly become time-consuming and costly, and the T-45 doesn’t have nearly the support or abundance of junkyard parts that the T-5 or TR-3650 do. Because of this, many people with an SN95 Mustang decide that instead, they’d like to simply upgrade to the T-56.

The T-56 transmission comes in many versions. The one that was used in the Terminator Cobra suffered from the same 10-spline input shaft weakness as the T-45. Thankfully there are aftermarket T-56 transmissions with 26-spline input shafts, which improve the beefiness substantially.

The T5 is also still being manufactured, with Tremec producing a new line of them that are substantially more heavy duty than their predecessors but that boast the same simplicity and durability of design.

Installing a New Transmission

Installing a new transmission is a great investment if you have a vehicle that you plan on using for a long time. Unfortunately, it does require a lot of forethought since the transmission is integral to the performance of your car.

You should select a transmission with a torque capacity that not only meets your current needs, but that also gives you room to grow. For example, some older T5 transmissions had a torque capacity of 300 lb-ft. While that is enough for a 1997 Mustang GT, which had a torque of 285 lb-ft, it wouldn’t be enough if the owner were considering modifications that would further increase the torque.

Thankfully, newer T5s have torque capacities of 500-600 pounds per foot, more than enough to meet your current needs and give you ample space to continue to improve your Mustang.

A new transmission frequently requires a new driveshaft as well. Thinking through this in advance and making sure that you do thorough measurements and research can help make sure you don’t have any unpleasant surprises mid-swap.

T-45 Summary

Though the T-45 transmission introduced a lot of features that are used in modern Mustang transmissions and was an improvement in many ways over the T-5 transmission, the fact that it was so short-lived meant that there was hardly time to fix the initial wave of problems before the T-45 transmission was already being phased out.

This leaves enthusiasts who have a T-45 equipped Mustang in an uncomfortable position. Improving the T-45 is certainly possible, and for many is the more sensible route to take, but replacing the entirety of the transmission creates additional room for growth for Mustang owners who feel that they’re still at the beginning of their Mustang-Tuner journey.

Regardless of whether you decide to improve your T-45 transmission or replace it entirely, CJ Pony Parts has the parts you’ll need to make your transmission upgrade a success.

Image Credit: Mustangs and Fords, StangNet

The Mustang's T-45 Transmission

Between 1996 and 2001, many Mustangs were equipped with T45 transmissions. Though these transmissions brought a slew of improvements that we still rely on today, there are several weaknesses that can be addressed through modifications.