History of the BorgWarner T-45
by Stan Peace, www.Pro-ForcePerformance.com
This article is a culmination of research begun in 2010; it
is periodically updated with new information and clarifications. The
author does NOT give permission to copy and re-post this on other websites
without providing credit to the author and a functioning link back to this
Questions, or requests for updates may be made by contacting the author through
The T-45 first appeared with the 1996 Mustang as a stronger 5-speed manual
transmission to mate with the new Modular 4.6 V-8 engine. It was used
until around February of 2001 when mid-production 2001 Mustangs began receiving
The T-45 was a BorgWarner design that was exclusive to the Mustang. Tremec
(Transmission Technologies Corporation - aka TTC) acquired BorgWarner's Light-Duty Transmission Division
around 1997. While the T-45 remained virtually unchanged, T-45 units produced by TTC bear the Tremec name as do all OEM replacement parts.
The T-45 a single-rail shifting mechanism that is somewhat similar to the T-5
and was carried forward to the T-56. The T-45 was the first Mustang manual
transmission to have a fully synchronized reverse gear. Some
versions of the T-5 had a "Reverse Brake" feature that employed an
extra synchro ring, but reverse gear was NOT fully synchronized in the T-5.
There were only three versions of the T-45 produced and they were tagged as
1381-001 - 1996-1998 Mustang GT
1381-002 - 1996-1998
1381-011 / TNET1386 / TSET1386 - 1999-2001 Mustang GT & COBRA
The T-45 can be divided into two designs. The early units were for 1996-1998
V-8 Mustangs and the later units were for the 1999-2001 models. Within the
1996-1998 years the transmissions were identical between the GT and the COBRA
models except for two items. First, the COBRA T-45 employed a 7-tooth
internal speedometer gear where the GT had an 8-tooth internal speedometer gear.
Second, the transmission cross-member mount for the COBRA models was
located further to the rear resulting in different tail housing castings between
the two models.
For 1999, Tremec invoked several changes attempting to make the T-45 more
reliable. This included stronger shift forks for all gears, a sturdier
throwout bearing sleeve on the front housing and carbon-fiber synchro rings for
gears 3, 4, 5, and reverse. Carbon-fiber rings for first and second gears
were made available later as replacement parts, but did not appear in the
production units. These rings for first, second, third and fourth gears are identical to
those used in the T-56.
One additional change for 1999 was the inclusion of an all-electronic
"OSS" speedometer sending unit. 1994-1998 Mustangs used an
electronic signal to drive the speedometer, but these signals were generated by
a "VSS" speedometer sending unit that was driven by a pair of
gears. Calibration for a "VSS" speedometer system was
accomplished by selecting the correct gears to drive the sending unit. For
1999 the OSS unit had no gears and was calibrated by settings in the
"Tune" of the Engine Computer.
It also appears that the 2001 Mustangs with the last production T-45's were
tagged TNET1386 and TSET1386 with no discernable differences from the 1381-011
units other than the tag.
The T-45 uses the same shifter base as the T-5 and enjoys a broad selection of
after market shifter choices that can improve the indexing of third gear on a
There is only one set of production gear ratios for the T-45. The ratios are all
3.37, 1.99, 1.33, 1.00, and 0.67.
The ratio for reverse gear is 3.22.
Updates to the T-45
Numerous Service Bulletins have been issued for the early T-45's. I won't attempt to cover these in
detail. While no longer available, Ford installed "updates" to a number of
for owners who complained of shifting problems with reverse gear while their cars were still under warranty. These
fixes focused on the Fifth/Reverse gear forks which were jamming and
breaking. Three stronger versions of the fork were produced as replacement
parts and the best-fitting part was selected as part of the service bulletin in
an attempt to correct the issues.
The stronger reverse forks were incorporated into the production T-45's
beginning in 1999 as well as stronger forks for gears 1-4. However,
forks in ALL of the production T-45's continued to be notorious for breaking.
One additional weakness in the shift forks that were addressed by Tremec
with the 1999 models is that the linkage, or selector "Shift Plates" were made
stronger to prevent them from fatiguing and snapping off. Unfortunately,
these improved parts were still not strong enough and continued to break.
The current official Fluid for a T-45 is Ford's Mercon-V which is a quality synthetic blend. The Mobil-1 meets the Mercon-V specification, but is also fully synthetic. It is a general
consensus that certain synthetic fluids have detergents in them that can damage the linings of the
non-carbon-fiber synchro rings used in the T-45 and should be avoided.
Gear oil and motor oil are not recommended and will damage the early style
synchro rings used in a T-45.
The T-45 is a rather strong transmission but its weak spot in a high-torque application is the 10-spline input shaft. These stock shafts tend to shear off when launching a 500 HP car at the drag strip. To remedy this, builders have been modifying original input shafts by grafting a new 26-spline front onto the gear.
This puts the T-45 at higher torque rating. Pro-Force now offers
26 spline input shafts for the T-45!
Customizations to the T-45
Numerous custom parts are available for the T-45 to resolve the inherent issues
that were never resolved by the manufacturer. Billet shift forks are
available for the 1-2 and 3-4 synchros that are much stronger to avoid breakage
as well as stronger Billet Shift Plates. The pesky
issues with reverse and fifth gears are eliminated with the use of Billet Keys
in the 5-R Synchro hub as well as a custom redesign
of the reverse hub and fork resulting in a "single-disconnect" design rather than
an off-balanced double fork design. For the 96-98 models, the
input/release bearing sleeve is available as a one-piece billet design to
T-45 to TR3650 INTERCHANGE INFORMATION:
Note: The TR3650 uses a different Shifter base than the T-45.
- A 1996-1998 T-45 can be replaced with either a 1999-2001 T-45 or a
2001-2004 TR3650 by using an electronic device called the
"Dallas Mustang Speed-Cal" to convert the speedometer signal.
- A custom, or modified cross member is needed to install a TR3650 in a 96-98
- A 1999-2001 T-45 can be replaced directly with a 2001-2004 TR3650.
- The reverse light switch from the T-45 is retained when converting to a
This article was last updated on 07/14/2019