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Tech Alley               "Where you find all the answers."

TREMEC® TKO Transmissions

TREMEC offers several different models of five speed transmissions**, and introduced a new lineup in 2004.  Here is a bit of the history of the TKO line.

The manual transmission line of Borg Warner is now owned (since 1998) by Transmission Technologies Corporation (TTC), however, the design remains unchanged between the two transmission lines. Borg Warner transmissions, for the most part, use a single rail gear selector and carbon fiber lined steel synchro rings, where the TREMEC transmissions have a single rail that selects and moves three shift rods internally. These three rods have spring loaded detents that make the transmission feel notchy during shifting. Instead of carbon lined steel synchro rings, the TREMEC TKO line is built with solid bronze synchros with no linings. It is for these reasons that the TREMEC TKO does not like to shift well above ~6,000rpms unless modified.  Carbon fiber rings are now available as well as several other modifications to improve shifting and durability.  Contact us for details.

Mid and front shift (front shift no longer available from TREMEC) location kits available for all models.

New in 2004

TREMEC changed its line of TR-3550 and TKO in 2004. (TKO-500/600 Press Release)  The TR-3550 was replaced by the TKO-500 and the TKO is now called the TKO-600.  There were several changes in the new line up.

The all new line of TREMEC TKO 5 speed transmission are the most versatile, strongest transmission of the series.  With eight available shift positions, three unique cross member mounting configurations, three available input shafts, optional gear ratios, dual electronic and mechanical speedometer pick-ups, neutral safety switch, and back-up light switch, this transmission does it all! 

How was this transmission improved?  The 83mm center distance was maintained, and upgraded the counter shaft from a 3 piece to a one piece design.  All the gears and shafts were upgraded to a higher alloy steel, while the aluminum shift forks were replaced with steel forgings and completely redesigned. 

The shifter has been upgraded to performance status with a unique adjustable biasing system to tune to your exact preference.  Eight different shift locations means the shifter will likely fit in your stock console.  

The TKO-500/600 features dual speedometer pick-ups, with both mechanical and electronic speed pickups. 

All cast iron shift forks for improved durability reducing failures with non-adjustable positive shift stops so it can not be over-shifted. 

New TKO-500

Ford TKO-500 is torque rated at 500ft/lbs. 10 spline input shaft with a 31 spline output shaft. 3.27 first gear with a .68od. Standard shift location is the rear "Mustang" shift point. Mid and front shift kits available. Main case bolt pattern remains the "toploader" pattern. 

GM TKO-500 has a 3.27 first gear with a .68od. Torque rating 500ft/lbs. Standard shift location is the rear "vintage Camaro" shift point but can be changed to several other shift locations. Main case bolt pattern is a "Muncie" 4 speed pattern. Call for details. 

New TKO-600   TKO-600_GM_small.jpg (180918 bytes)

Ford TKO-600 is torque rated at 600ft/lbs. 26 spline input shaft with a 31 spline output shaft.  Comes in two standard over drive configurations 1) 2.87 first gear .82od and 2) 2.87 first gear with .64od.  Standard shift location is the rear "Mustang" shift point.  Mid and front shift kits available.  Main case bolt pattern remains the "toploader" pattern.  

GM TKO-600 is torque rated at 600ft/lbs.  26 spline input shaft with a 31 spline output shaft.  2.87 first gear .82od.  Standard shift location is the rear Muncie 4 speed shift point.  Mid shift kits available.  Main case bolt pattern remains the "Muncie" 4 speed pattern.

Model (ft/lb) input
1st 2nd 3rd 4th 5th
TKO 500 500 10 31 3.27 1.97 1.34 1.00 .68
TKO 600 600 26 31 2.87 1.89 1.28 1.00 .82
TKO 600 600 26 31 2.87 1.89 1.28 1.00 .64


See our TKO FAQ's for more answers about the TKO series 5-speed transmissions.

Custom Configurations

TREMEC TKO transmissions can be shifted from three different locations. Front, Mid, and Rear. From the factory they are configured as a rear shift. To change the location, a mid or front shift kit (front shifter is obsolete) are install and the rear shifter location is capped off with a provided plate.

TREMEC TKO transmissions are a great replacement for Ford toploader four speeds or GM Muncie fours as they have been configured to bolt up to the stock bellhousings.  Keep in mind that TREMEC TKO's are larger and taller then their 4 speed counter parts.  We offer TREMEC TKO's with a shortened input shaft that will bolt right in or if you only need the input shaft and bearing retainer give us a call. The only parts needed to convert from a three or four speed is a cross member, shift lever, shift ball, and shorter speedometer cable. The drive shaft length is not affected for the Ford conversion as the transmissions are the same length. The slip yoke may have to be changed to match the output shaft.

Ford 3550

The Ford 3550 is a step up from a T-5z with 3.27 first gear and a .68od.  Torque rate increased to 375ft/lbs.  The input shaft has the same 10 spline input shaft as that of a 93 and earlier T-5.  The TKO main case bolt pattern is different than the T-5 so a TKO bellhousing is needed when switching out a T-5.  The output shaft is a standard Ford 28 spline that has been used since the C4 automatic and toploader 4 speed days.  Since the TKO's have the same bolt main case pattern as the early 3 or 4 speeds, it can be bolted directly to the 3 or 4 speed bellhousing when the input shaft is shortened to match.  We offer both the shortened input shaft and bearing retainer as well as ready to install new shortened input TKO's.  Call us for details and/or check our product catalog on-line.

The 3550 has been replaced by the new TKO 500. See New for 2004 (above) for further details. 

GM 3550

The GM 3550 is designed to provide a five speed replacement to the Muncie four speed transmission.  The input shaft and main case are ready to bolt to a four speed bellhousing.  Input shaft is a 26 spline with a GM pilot. Output shaft remains a 28 spline so the slip yoke will have to be changed.

Ford 3550-II

The Ford 3550-II is the same as the 3550 with a .83 overdrive.  Great for road racing when the 1:1 ratio of a four speed is not enough and a .68 over drive is too tall.  Works well for off roading as well in 2x4 trucks and SUV's.

Ford TKO

The Ford TKO transmission has the same layout and gear ratio as the 3550 but with stronger 26 spline input shaft and 31 spline output shaft and stronger 3rd gear. It is torque rated to 450ft/lbs.


The GM TKO is designed to be a replacement five speed transmission.  However this time the output shaft is a 31 spline with the stronger 3rd gear.


The TKO-II is the same as the TKO but is equipped with a .83 overdrive instead of a .63 overdrive.  Again great for road racing or off roading. Torque rating increase to 475ft/lbs but has been known to handle much more.

All four models have the same overall dimensions. The 3550-II and TKO-II are best suited for road racing where the .83 overdrive comes in handy on the long straight-a-ways.


Model (ft/lb) input
1st 2nd 3rd 4th 5th
3550 375 10 28 3.27 1.98 1.34 1.00 .68
3550 II 375 10 28 3.27 1.98 1.34 1.00 .83
TKO 450 26 31 3.27 1.98 1.34 1.00 .68
TKO II 475 26 31 3.27 1.98 1.34 1.00 .83

Tremec 3550, 3550II, TKO, TKOII

TREMEC 3550, 3550-II, TKO, TKO-II 

**Note: The T5 is also manufactured by TREMEC but is treated separate from the 3550/TKO transmissions.


T-45    T-5    TKO    TR-3550    TR-3650

T-56    T-56 Magnum    S-197 Magnum