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Mustang Tremec TKX Transmission Swap Guide

Created by Jeff Jimenez
Last Updated 5/18/2022

Adding power to any car is a hassle to put the power to the wheels through the stock transmission. That is why many turn to the Mustang TKX Swap, follow along and we will guide you on all of the needed steps for this swap.

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FOLLOW: 79 93 mustang , 94 04 mustang , transmission , tkx , driveline , mustang coyote swap , tech guide

Ford Mustang Tremec TKX 5-Speed Transmission Swap Guide  - Ford Mustang Tremec TKX 5-Speed Transmission Swap Guide
Jump To: 79-93 | 94-95 | 96-98 | 99-04 | FAQ

Innovation has always been a necessity in the automotive aftermarket world. It is needed in the never-ending quest to be faster, lighter, and stronger than the next car. Tremec’s latest innovations might bring about the end of the iconic TKO transmission. Recently Tremec released the TKX 5-Speed Transmission, which brought a host of improvements over the older TKO500 and TKO600 transmissions. These include 600 lb-ft torque capacity and 8,000 RPM shifting capability, to name a few. You can read more about both versions of this transmission in the links below.

As soon as these new transmissions hit the market, Mustang enthusiasts asked, “how do you swap a Tremec TKX transmission into your Mustang?” In this article, we will take a look at some of the needed parts and modifications needed to swap this new transmission into a few different generations of Mustangs. The best part about the TKX transmission swap is that it is nearly identical to the Mustang TKO transmission swap of old, and they require no transmission tunnel modifications in the 79-04 Mustangs.





How To Swap A Tremec TKX Transmission Into A Fox Body Mustang (1979-93 5.0L Engines)

In this section, we will take a look at doing this swap on the iconic 5.0L pushrod engines that made the 1979-93 Mustangs so famous. Below is the parts list that is needed to do this swap. These swaps will require you to purchase a TKX-specific bell housing and cross member. See the most popular options in the parts list below. You will also need to convert your existing driveshaft with a 31 spline yoke or purchase a new one with a 31 spline yoke already installed. Lastly, you will need a clutch that supports a 26 spline input shaft. We cover this topic further below in this tech guide.

Fox Body TKX Transmission Swap Parts List:

TKX Specific Bellhousing
TKX specific crossmember and supporting parts:
31 Spline Driveshaft Conversion
Pick out the correct spline clutch to fit your build (see below for more details)
1979-98 Mustang speedometer correction:

All Tremec TKX transmissions include a 7 tooth driven gear. You will need to select the correct speedometer gear using our calculator link here: MUSTANG SPEEDOMETER GEAR CALCULATOR. Another great option to fix your speedometer without replacing speedometer gears is to use the Abbott Electronic Speedometer recalibrator. It allows you to electronically adjust your speedometer on your 1994-98 Mustang without having to reflash your ECU or replace speedometer gears.





How To Swap A Tremec TKX Transmission Into A 1994-95 Mustang (5.0L Pushrod Engines)

Doing this swap on a 94-95 Mustang that has a 5.0L pushrod engine is very much the same as the Fox Body swap seen above. There is a different crossmember that is needed and the driveshaft will require some lengthening or a spacer (see parts list below)

1994-95 Mustang TKX Transmission Swap Parts List:

TKX specific bellhousing
TKX specific crossmember and supporting parts:
31 Spline Driveshaft conversion and modifications
Pick out the correct spline clutch to fit your build (see below for more details)
1979-98 Mustang speedometer correction:

All Tremec TKX transmissions include a 7 tooth driven gear. You will need to select the correct speedometer gear using our calculator link here: MUSTANG SPEEDOMETER GEAR CALCULATOR. Another great option to fix your speedometer without replacing speedometer gears is to use the Abbott Electronic Speedometer recalibrator. It allows you to electronically adjust your speedometer on your 1994-98 Mustang without having to reflash your ECU or replace speedometer gears.





How To Swap A Tremec TKX Transmission Into A 1996-1998 Mustang (4.6L Engines)

In 1996 Ford introduced the 4.6L modular engines. These came in two different variations during this timeframe – SOHC and DOHC. This swap will require you to get a bellhousing, crossmember and in some cases, you may need a driveshaft spacer. Unlike the previous swaps, you will not need to purchase a 31 spline driveshaft as the factory driveshaft is 31 spline. The spacer will vary depending driveshaft and engine combination. We always recommend you purchase a spacer before starting the installation.

TKX specific bellhousing
TKX specific crossmember and supporting parts:
Additional 1996-1998 Fitment Notes:
  • Speed pickup conversion for mechanical speed pickup to electrical.
  • Drive Shaft Spacer may be necessary. We have found the SVE 11/16th driveshaft spacer is a great fit if you need one.
  • This is a great opportunity to upgrade your driveshaft to the Ford Performance M-4602-J aluminum driveshaft. It is a great way to reduce rotational mass and improve the overall strength of your driveshaft.
  • Pick out the correct spline clutch to fit your build (see below for more details)
1979-98 Mustang speedometer correction:

All Tremec TKX transmissions include a 7 tooth driven gear. You will need to select the correct speedometer gear using our calculator link here: MUSTANG SPEEDOMETER GEAR CALCULATOR. Another great option to fix your speedometer without replacing speedometer gears is to use the Abbott Electronic Speedometer recalibrator. It allows you to electronically adjust your speedometer on your 1994-98 Mustang without having to reflash your ECU or replace speedometer gears.





How To Swap A Tremec TKX Transmission Into A 1999-2004 Mustang (4.6L Engines)

Like the 94-98 SN95 Mustangs we covered above, the New Edge Mustang TKX transmission swap will require you to upgrade your bellhousing, cross-member, and driveshaft. In 1999 the Mustang saw a redesigned facelift; it also saw a move away from mechanical speed pickups and a few new factory transmissions/engines in the 2003-04 SVT Cobras. Those Cobras would require a few extra modifications if you moved away from the T56 Transmission in your Terminator Mustang (see below).

It is also important to point out that Ford changed from mechanical to electronic speed pickups on the transmissions during this era of Mustangs. When we are writing this, we do not have a turn-key solution to fix this. That means you will need to find to set this to get your speedometer to read correctly.

TKX specific bellhousing
TKX specific crossmember and supporting parts:
Additional 1999-2004 Fitment Notes:
  • Speed pickup conversion for mechanical speed pickup to electrical.
  • Drive Shaft Spacer may be necessary. We have found the SVE 11/16th driveshaft spacer is a great fit if you need one.
  • This is a great opportunity to upgrade your driveshaft to the Ford Performance M-4602-J aluminum driveshaft. It is a great way to reduce rotational mass and improve the overall strength of your driveshaft.
  • Pick out the correct spline clutch to fit your build (see below for more details)
99-04 Mustang speedometer correction:

For the 1999-2004 Mustangs, you will not need any speedometer gears or recalculation tools to correct your speedometer. The TKX transmission includes a digital speed sensor on the passenger side of the housing. You will need to lengthen your stock wiring harness to reach this speed sensor. Speed correction can be done using your handheld tuning device or a custom mail order tune.





What Clutch and Flywheel Is Right For Your TKX Swap?

At this time, the TKX transmission is available in 10 spline and 26 spline input shaft options. The first step in selecting the correct clutch will be to validate what transmission you purchased. Once you have confirmed the input shaft, use the following article to help determine what clutch is best for how the vehicle will be driven and what engine option you are running. Just match up the clutch you select and make sure it has the corresponding spline count to match your new TKX transmission.

MUSTANG CLUTCH BUYERS GUIDE

Can You Use A Tremec TKX Transmission For Your Coyote Swap?

The short answer is YES! This is a great option when compared to factory Mustang manual transmissions such as the T5, T45, or 3650. Even when compared to the mighty T56 and T56 magnum transmission, this new Tremec TKX can hold its own with its 600 lb-ft torque capacity and 8,000 RPM shifting capability out of the box. That means it can stand up to the higher horsepower and high rpm shifting that makes the Coyote Swap so popular.

Follow the abovementioned steps to use the TKX transmission with your 1979-04 Mustang Coyote Swap. You will need to use a modular motor bell housing to attach this transmission to your 5.0L Coyote motor. You can see the bell housing options below. You can also see more Coyote swap parts and tech here: Mustang Coyote Swap Parts & Guides.

Mustang Coyote Swap TKX Specific Bellhousings

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TREMEC TKX TRANSMISSIONS

Check out the currently available options for the Tremec TKX transmission below.

TREMEC TKX BELLHOUSINGS

Check out the different bellhousing options available for your Mustang Tremec TKX swap.

TREMEC TKX CROSSMEMBERS

Swapping a Tremec TKX transmission into your Mustang will require you to upgrade your cross-member. Don't forget the installation hardware and transmission mounts while doing this swap.

TREMEC TKX DRIVESHAFTS

Doing a Tremec TKX swap may require replacing your driveshaft or adding a spacer. See some of the most popular options below.