Swapping a five speed transmission into an early Mustang,
Falcon, Cougar, or almost any early Ford could not be
any easier these days. Many of the five speed
transmissions found in late model Mustangs can be
installed with little modification.
1965 - 66 Mustang
For a 1965 - 1966 Mustang we recommend a T-5
transmission for engines making under 450hp. The T-5 fits much better
than a larger TREMEC TKO due to clearance
issues with the transmission tunnel. TKO
transmissions can be installed but it requires
modifying the transmission tunnel. A T5 swap in
these cars is straight forward whether swapping an
automatic or a Toploader. Even the
transmissions can be swapped with a T5. The only
modification needed to install a T-5 is to
clearance the right side of the shifter opening by
Check out the November 2011 issue of Mustang
Monthly for a full installation tutorial of a T5 into a
'67 GT350 Clone.
1967 - 73 Mustangs
1967 - 1973 Mustangs have all the same options as the 1965-66 Mustangs.
In addition to the T5, the TREMEC TKO-500 and TKO-600
transmissions are available as they will fit within the
These transmissions are larger and heavier than a T-5 or
four speed and require more transmission tunnel room
found in these larger cars. The TREMEC 3550 and TKO500
have the same bolt pattern as 3 or 4 speeds but have the
same longer 10 spline input shaft as the T-5. The reason
the input shaft is longer is to provide additional
clearance needed for the cable operated bellhousings
used in Fox body Mustangs. The 10 spline input
shaft may be an advantage if you are trying to preserve
a clutch used with the 4 speed. However, if the
clutch is not a concern then the TKO600 is the best
choice for high horsepower or big block cars.
Shifter location on a T5 or TKO lines up with the opening in the floor
with a conventional long input shaft. With the
shortened input shaft the shifter is slightly forward
requiring a little more clearancing of the tunnel.
It is not recommended to use the shortened input shaft
with cars with consoles as the shifter is moved too far
forward relative to the console.
Some of the additional parts needed to swap a TKO
into a 67-70, or 71-73 Mustang/Cougar is a TKO cross
member, as the mounting position is further back, a
cable, speedo gear and shifter lever and ball.
For Mustangs making more than 450hp, the TREMEC TKO and TKO600 is the
next step up with a 26 spline input shaft and a 31
spline output shaft. The overall layout is the
same and again with a shortened input shaft, the TKO can
be bolted to any small or big block early bellhousing.