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Everything You Need To Know About Foxbody Mustang Transmissions

Written By: Connor MC

Listed below is everything you need to know in regards to the T5, TKO-500, TKO-600 and Tremec T56 transmissions in relation to 1979-1993 Foxbody Mustangs.

American Muscle

Foxbody T5 Transmission Limits

Ford introduced the Borg-Warner made T5 transmission into the Mustang line up for 1983. Replacing the SROD, the T5 is a lightweight 5-speed transmission intended to increase performance and gas mileage during the Fox era. Since its inaugural debut in 1983, Ford has made many revisions to the T5 over the years, leaving some quite different than others. The most well known difference is the Non World Class T5 (NWC) and World Class (WC) T5. Is one specifically better than the other? Use the links below to learn more about the T5 manual transmission and how it changed throughout the years. The T5, overall, is a good transmission for how it is built. The problem with it, as many owners already have witnessed, is that the T5 is pretty much at its limit on a stock Mustang. It is a well designed, well functioning transmission, but it is not well applied in the Mustang. The T5 is a light-weight transmission, and does not fare well at anything above stock Foxbody power levels (225 HP, 300ft-lbs)

T5 Quick Sheet


TypeYearTorque RatingRecommended Gear Oil
Non World Class1983-1984265 ft-lbsDextron III, Mercon, Mercon V ATF
World Class1985-1989265 ft-lbsDextron III, Mercon, Mercon V ATF
World Class1990-1993300 ft-lbsDextron III, Mercon, Mercon V ATF

Non World Class (NWC) Breakdown

As mentioned, Ford began equipping Mustangs with the T5 manual transmission in 1983. The first version of this Borg-Warner transmission used a 2.95 ratio first gear and a 0.63 ratio overdrive for V8 Mustangs. First (1st), second (2nd) and third gear (3rd) ride on a solid output shaft. The counter gears ride on straight cylindrical bearings with a thrust washer at the front of each bearing (for load support). Synchros are made of solid bronze. Dextron II was originally used, but as it is not available any more, Tremec now recommends 50W straight gear oil in its place. Everything said and done, the 1983-1984 NWC T5 is rated at 265 ft-lbs of torque.

The T5 was also used in the 2.3L four-cylinder Mustang, this model featuring a 3.97:1 first gear and a smaller pilot bearing, which resulted in a decreased torque capacity rated at 245 ft-lbs. The 4-cylinder transmissions are NOT a direct swap for 5.0L versions. However, they can be converted to work with a V8. This will be covered in more detail in a separate article.

World Class (WC) T5 Breakdown

In 1985, Ford adopted the World Class version of the T5. Initially, it was not any stronger than the initial Non World Class version. Rather, Borg Warner made several changes to the bearings and synchros such that the transmission could be marketed worldwide (thus the name World Class).

With the World Class transmission, Ford selected a 3.35 gear set and a 0.68 over drive. Needle bearings were installed under the first 3 gears to reduce drag, whilst tapered bearings replaced the bronze thrust washers. Main shaft synchros were changed to fiber-lined steel plates (fifth gear remained bronze). These synchros provided added friction to further slow the gears for a smooth shift (particularly at high RPM). Despite these changes, the torque rating of the transmission did not change, and is still rated by Borg-Warner at 265 ft-lbs.

1990 to 1993 Mustangs continued to use the World Class T5 transmission, but with a few more changes. Ford upgraded the gear set by increasing the nickel content, thereby strengthening the gears. Third and fourth gear synchro linings were changed to carbon fiber. Because of the gear set improvement, torque rating was increased to 300 ft-lbs, making the 1990-93 T5 the strongest production transmission to be found in the Fox platform.

Non World Class and World Class T5 Differences

To clarify, back in 1983 when the T5 was introduced into the Mustang lineup, Borg-Warner did not call the T5 transmission non world class. Rather, the term "Non World Class" came about only when in 1985, Borg-Warner released the T5 globally, under the name World Class. From that point on, there needed to be a way to distinguish between the early model and late model (World Class) T5 transmissions. Therfore, the early models began being referred to as the Non World Class transmission. (Just like there is a HO 5.0L V8, and a non-HO 5.0L V8)

Internally, there are some differences. First off, as mentioned above in the breakdown sections, NWC T5's used a 2.95:1 first gear and a 0.63 ratio overdrive, whereas World Class versions used a 3.35 first gear and a higher 0.68 ratio overdrive. Synchros changed from solid bronze to fiber-lined steel, needle bearings were installed on the mainshaft cluster as opposed to the solid shaft design of the Non World Class T5, and finally, in 1990, nickel content was increased making the gear set in the 1990-1993 Mustangs the strongest ever. In a nutshell, T5's produced from 1983-1989 were rated at 265 ft-lbs of torque, and 300 ft-lbs from 1990-1993.

Are the NWC and WC Transmission Interchangeable? Yes, both transmissions are interchangeable. There are no mounting differences or changes in the case that would prevent one being swapped for the other.

Which is better, the NWC or WC T5? Purely from a power aspect, the World Class transmission from 1990-1993 is the best, as it is rated at a capacity of 300 ft-lbs. However, some owners who have used both versions of the transmission reported the NWC version as shifting smoother in stock form.

The Limits of the T5 Transmission

The T5 is a light-weight, light-duty transmission. For what it is (roughly 80 lbs and pretty compact), it is a pretty good transmission. However, throw one of these T5's in a Mustang, and it is an entirely different story. Essentially, any T5 transmission is already at its limit - even on a stock Mustang. Real world applications have shown that the T5 transmission is pretty easy to break if any amount of power (the like of which a Mustang is capable) is put through it. For example, I blew my own T5 transmission on a stock Fox running BFGoodrich radial T/A tires. On the other hand, others claim to be running around the streets with 400-500 horsepower and report no issue (rather, they report it hasn't broken yet!).

Realistically, if you drive carefully and don't abuse it (meaning no power launches, redline full throttle shifts, or hook hard), the T5 can last. But, this could be said about anything, really. If you baby any type of object, chances are it will last a while.

For stock Mustangs that aren't going to be launched hard, the stock T5 will work very well and should continue to work well on mildly modified Mustangs. Start taking the Mustang to the track, however, and it is only a matter of when, not if, the T5 will break.

Upgrading a T5 Transmission

Do I need to upgrade my T5 transmission? Well, it depends. If you're driving around in a stock Foxbody Mustang, the factory T5 should be adequate. If you are planning on building the engine, then it is at this point that you will want to consider upgrading the T5. Personally, however, I would run the stock T5 until it blows, and only once it blows, upgrade it or swap it out. Who knows, maybe you'll be one of those lucky guys that are somehow running around with 400 horsepower and their T5 has never worked better - or so they claim.

On a more serious note, when you decide it is time to upgrade, it is still possible to do so. Presently, in 2016, it seems that T5 parts are slowly dwindling and there are less options available on the market. G-Force, Astro Performance and Promotion Powertrain seem to be the only three companies still offering parts and upgrades for the T5 transmission. All three companies offer to sell the upgrade kit (internals) separately or pre-installed (if you pick the latter, you must send in your original T5 as a core). It's possible to get stock rebuild kits (yuck) or upgraded versions that will support as much as 575 ft-lbs.

Alternatively, you could do away with the T5 altogether and throw in a TKO-500/TKO-600 or even a Tremec T56 (6-speed transmission, woooo!). While not a direct bolt-on, both are "relatively" easy to get in there as the aftermarket has come up with all the necessary pieces to make the conversion pretty simple (bellhousing, cross-member, shift fork etc). Keep in mind these transmissions use a 26-spline input shaft, so you will have to change the clutch too (stock clutch is 10-spline). For more information on transmission swaps, check out the TKO-500 TKO-600 swap guide immediately below.

Foxbody TKO-500 & TKO-600 Swap

The TKO-500 is a 5 speed overdrive transmission introduced in 2004 to replace the TR-3550. Rated for 500 ft-lbs of torque, the TKO-500 is very stout. There are two models available. One comes with a 10-spline input shaft and one with a 26-spline input shaft. The output shaft has 31-splines for both models.

The TKO-600 is very similar to the 500, except even stronger. Rated for 600 ft-lbs of torque, the TKO-600 has different gearing than the TKO-500 and has two available over drive ratios. The TKO-600 only comes with a 26-spline input shaft. As such, when installing in a Foxbody or SN95 you will have to match this transmission with a new 26-spline clutch.

TKO-500 - 500 ft-lbs, 10-spline or 26-spline input shaft (this requires you to change the clutch to match)
Gear ratios: 1st-3.27, 2nd-1.97, 3rd-1.34, 4th-1.00, 5th-0.68

TKO-600 - 600 ft-lbs, 26-spline input shaft
Gear ratios: 1st-2.87, 2nd-1.89, 3rd-1.28, 4th-1.00 and an overdrive of either 0.82 or 0.64 (5th gear).



What do I need to install a TKO-500 or TKO-600 in a 1987-1993 Foxbody?

26-spline clutch (only if the transmission has a 26-spline input shaft)

  • Single Disc
  • Dual Disc
  • Adapter bellhousing
    • Ford Racing #M-6392-R58 (this is actually the stock piece from a 1995 Cobra R)
    • Quicktime #RM-6060, #RM-6065 (SFI approved)
  • 31-spline driveshaft yoke
    • Ford Racing #M-4841-A (uses 1330 style Moog 270 U-joints)
  • Crossmember modification
    • You can modify your own crossmember (potentially), or, for $70;
    • Ford Racing #M-5059-A or;
    • An AOD crossmember may work. Owners on various forums have reported doing this

What do I need to install a TKO-500 or TKO-600 in a SN95 Mustang (94-99)?

26-spline clutch (if the input shaft is 26-spline, otherwise use a 10-spline clutch)

  • Single Disc
  • Dual Disc
  • Adapter bellhousing
    • Ford Racing #M-6392-R58 (stock piece from a 1995 Cobra R)
    • Quicktime #RM-6060, #RM-6065 (SFI approved)
  • 31-spline driveshaft yoke
    • Ford Racing #M-4841-A (uses 1330 style Moog 270 U-joints)
  • Crossmember modification
    • Some are able to just flip their stock crossmember around and it works, others need to elongate the holes
    • Lengthening the driveshaft by 0.625" (a shop can do this)
    • OR use a spacer, Steeda #555-7707
    • OR some people don't bother with any of this at all. Results may vary.
  • New clutch fork

TKO-500 vs TKO-600, which should I get?

If you are making over 500 ft-lbs of torque, then the answer to this question is easy. You need to go with the stronger TKO-600. However, if torque rating is not a factor then there is a general rule of thumb. As the gear ratios of each transmission are slightly different (the 500 has a shorter first gear), it is recommended to use a TKO-600 when the differential gears are 3.73 or lower (3.90, 4.10 etc). A TKO-500 is better suited for 3.55 and higher (3.27, 3.08 etc). If you will be using a TKO-500, it is recommended to opt for the 26-spline input shaft version. Even though this necessitates changing the clutch, overall it is stronger and less likely to strip. If a TKO-600 fits the bill, remember that there are two available overdrive ratios - either 0.82 or a much higher 0.64.

What about the shifter?

If you purchase the transmission new, it comes with a shifter from Tremec. All you need to add is your own handle. The shifter for both of these transmissions will line up in the factory location. Aftermarket performance shifters are available if you wish to shorten and improve shift feeling.

Cons of a TKO-500 and TKO-600

Despite the great power and torque capacity of these two transmissions, there are a couple of disadvantages. First and foremost, the TKO series transmissions are considerably heavier than a stock T5. Furthermore, they do NOT shift as smooth, especially at high RPM, and are noticeably noisier than the older T5. Notchy shifts can be alleviated by replacing the stock Tremec shifter with an aftermarket unit from Steeda.

Foxbody Tremec T56 Magnum and Ford T56 Swap Guide

Why put in a Tremec T56 transmission? Well, there are a lot of reasons. First off, the T56 is capable of handling massive amounts of power. The Magnum version is currently rated at 700 ft-lbs, with further upgrades available. The T56 is also a great shifting transmission. It is very quiet, smooth and does not suffer the same high RPM problems that plague the TKO series. Presently, it is one of the best (if not the best) heavy-duty manual transmissions available.

T56 Magnum vs. Ford T56

A T56 Magnum is what you buy new off the shelf. A Ford T56 is a T56 that was installed by Ford in a Mustang (2000 Cobra R, 2003-04 Cobra), thus we can call it a Ford T56 or Cobra T56 - both terms reference the same thing. T56 Magnums come with a 26-spline input shaft and 31-spline output shaft whereas a Cobra T56 has a 10-spline input shaft and 27-spline output shaft. This means a Ford/Cobra T56 is compatible with your stock clutch setup (10-spline, 10.5" clutch). If you buy a T56 Magnum, you will need to change your clutch for one with a disc that has 26-splines to match the input shaft. However, Ford DOES sell an aftermarket T56 transmission - this is the Magnum version. For the purpose of this article, when I make reference to a Ford T56, I am reffering to a T56 that came equipped, from the factory in either a 2000 Cobra R or 2003-2004 Cobra Terminator. To clarify, see the identification table below.

Magnum T56 is currently rated at 700 ft-lbs in off-the-shelf trim. The Ford models, depending on which year Cobra you take it out of, are usually rated between 450-550 ft-lbs. Not as strong as the Magnum, but no slouch either. Ford T56s also have the advantage of being cheaper, as they are generally only bought from the second-hand market.

T56 Identification

TagApplicationInput SplinesOutput SplinesGear RatiosTorque Rating (ft-lbs)
TUET-2060Cobra R10272.97 2.07 1.43 1.00 0.84 0.56 2.90R450
TUET-169403-04 Cobra10272.66 1.78 1.30 1.00 0.79 0.63 2.90R450
TUET-7484
TUET-8274
Magnum26312.66 1.78 1.30 1.00 0.80 0.63 2.90R
2.97 2.10 1.46 1.00 0.74 0.50 2.90R
700


See here for further details

Magnum T56 Into a Foxbody

Here are the parts needed to swap a Magnum T56 (which is what you get when you purchase new from a Tremec dealer) into your Foxbody.

  • 26-spline clutch1
  • Crossmember
    • AJE #MU-7061
    • Stiffler #TCB-M02
  • Bellhousing2
    • Quicktime #RM-8031 - clutch fork 7 o'clock position
    • Quicktime #RM-8030 - clutch fork 9 o'clock position (same as stock T5 in Foxbody)
      • Requires McLeod midplate 8705-12
      • Use Foxbody clutch fork Ford #E6ZZ-7515-A
  • Driveshaft: Total length should be ~42.8"-43.5". You should have 3/4" of slip yoke visible at the transmission when the driveshaft is bolted to the rear axle flange. In order to obtain this you can:
    • Shorten the stock Foxbody driveshaft by ~1.5-2", OR;
    • use a 2003-2004 Cobra driveshaft (aluminium)

Every car is slightly different and the driveshaft length should be measured for optimal fitment. Car needs to be on the ground to obtain an accurate measurement. Depending on the mishmash of parts you end up with, you either will use a stock 1330 u-joint or need a conversion 1350/1330 u-joint.

  • 31-spline yoke: If it did not come with your driveshaft already (or if you shortened the stock one) - Ford Racing #M-4841A-31
  • Transmission mount: Energy Suspension #4.1104G or Prothane #6-1608-BL
  • Clutch cable: you will likely need a longer clutch cable. Presently, unable to confirm just how long.
  • Speedometer: Magnum T56 uses an electronic VSS. If you want to retain your stock mechanical gauges, you can have a shop modify the tailhousing to accomodate a mechanical drive system, or you can use the Abbott Tach CableX conversion box (converts VSS to mechanical). Otherwise, purchase and install a compatible electronic speedometer (Autogauge).
  • Lockout solenoid: You have three options:
    • Using the following pigtail connections, GM #12101857 or ACDelco #PT249 (cheaper), run the reverse lockout solenoid to a simple toggle switch mounted in a convenient place up front. Once installed and connected, simply flick the switch to disable the lockout and easily shift into reverse. When underway, flick the switch back and the lockout will once again become engaged.
    • You can unbolt and remove the solenoid and plug the hole using a 1" pipe plug. You will have to tap the hole. You could also remove the solenoid internals (plunger and spring) and re-install the solenoid (which is now empty) back in place.
    • Don't bother with any of this and simply just muscle the transmission into reverse (yes, this can be done.)

Notes on a Magnum T56 Install

If using a twin disc clutch (for example, a McLeod RST), further modification is usually necessary. Due to the extra thickness of a dual disc setup, a shorter pivot stud (for the clutch fork) is required. A special throwout bearing or bushing may be needed too. It is best to get an adjustable pivot ball, no matter which clutch kit you use.

The difference in bellhousings is the position of the clutch fork. Foxbody Mustangs (1983-1993) used a clutch fork at the 9 o'clock position, whereas SN95 Mustangs used a clutch fork position of 7 o'clock. If you want to guarantee proper clutch fork fitment, in relation to any starter, flywheel or exhaust setup, then you should use the kit that retains the regular T5 position of 9 o'clock - Quicktime #RM-8030, McLeod #8705-12. This of course is more costly.

Changing the clutch fork position to the 7 o'clock version may cause the fork to have clearance problems, cable problems or otherwise interfere with select aftermarket headers. This is not always the case, but there is a possibility of such a conflict occuring. Of course, this setup is cheaper. This is only something you need to take into consideration when installing a T56 into a Foxbody Mustang. SN95 Mustangs can utilize Quicktime bellhousing #RM-8031 (7 o'clock position) without worry.

Some owners report having clearance issues in the transmission tunnel and that the tunnel needed some "massaging" to have the T56 fit. This seems to be most commonly encountered when the stock crossmember has been modified in attempt to be re-used, or a custom one has been fabricated. Others have reported no issue at all. Furthermore, depending on your exhaust setup, modifications may need to be made there in order to have no interference. Some owners have had to modify the x/h-pipe, bend exhaust, move hangars and even relocate the catalytic converters. I guess every Foxbody install is somewhat unique.

Installing a Ford T56 into a Foxbody

Installing a Ford version T56 into a Foxbody Mustang is essentially the same thing as above. In this case however, you do NOT need a 26-spline clutch, as Ford T56 models maintain a 10-spline input shaft and are thus compatible with regular OEM-style Mustang clutches. Which bellhousing and resulting clutch fork position is left up to you, but again, recall that 83-93 Foxbody Mustangs came with a T5 using a 9 o'clock fork position. Any Ford version T56 transmission will have come from a later model Mustang that used a 7 o'clock position. For best fit, it is recommended to revert back to the stock 9 o'clock position, but this entails purchasing an additional adaptor piece from McLeod. For further clarification, read note #2 above.

  • Clutch - retains stock 10-spline clutch
  • 27-spline slip yoke: Since Ford T56s (from production Cobras) use a 27-spline output shaft, you will need to use a 27-spline driveshaft yoke. Ideally, you will get a matching driveshaft and yoke together.
  • Speedometer: Some Ford T56's came equipped to use a mechanical speedo. In this case, you may only need a longer cable (92", from a 1991 F150 supposedly does the trick). Some owners report being able to re-use the stock cable whereas others did indeed need a longer one. For electronic speedo equipped T56s, you need to change to an electronic speedometer, or use a Abbott Cable X conversion box. (Same as Magnum, above)

Installing a T56 into an SN95

With an SN95, we don't need to worry about the bellhousing and clutch fork. Here are the revisions necessary to install a T56 into an SN95.

  • Clutch
    • match with number of splines on input shaft. See note #1 above if using a dual disc clutch.
  • Bellhousing
    • 94-95 5.0L: Quicktime #RM-8031
    • 1996 4.6L: If you have a Ford T56 (out of a Cobra) that comes with the bellhousing, you can use that as-is. If you are missing the bellhousing, you need Quicktime #RM-8080
  • Clutch fork
  • Crossmember
    • You can buy new, or there are multiple ways to modifiy the stock crossmember to work. It gets a bit complicated, so with that in mind, for further information on crossmember modification, check out this great link from modular fords.

You can reuse your stock tranny crossmember on the T-56. For the mount you will either have to get the Prothane Conversion mount (part number 6-1608) or get a mount from an F-body car that used a T-56. I used an F-body tranny mount on mine and had to drill one hole in the tranny crossmember. I later swapped to the Prothane conversion mount, it's much nicer.

You will have to move your tranny crossmember mounts back or forward as well. It will depend on whether you are swapping into a GT or a Cobra. On a Cobra you will move the mounts forward on a GT you move the mounts back. On the Cobra you use the rear hole on mount in the forward hole on the frame, and then drill a new hole for the forward hole. Vice versa on the GT's (they need to move back). -Helomech74

  • Buying crossmember new:
    • 1994-1998 Mustang - AJE #MU-7061
    • 1999-2004 Mustang - AJE #MU-7070
  • Driveshaft: Total length should be ~44.7 from front u-joint center to rear u-joint center. 3/4" of yoke should be visible.
  • Slip yoke: Match with the number of splines of the output shaft. Depending on what transmission you have, you either need a 27-spline yoke or a 31-spline yoke.
  • Lockout solenoid: Using the following pigtail connections, most guys run the reverse lockout solenoid to a simple toggle switch mounted in a convenient place up front. Once installed and connected, simply flick the switch to disable the lockout and easily shift into reverse. When underway, flick the switch back and the lockout will once again become engaged. Or, other guys don't bother and just muscle the shifter into gear.
    • GM #12101857 or ACDelco #PT249 (cheaper)
  • Speedometer: For electronic speedometers, use Dallas Mustang Speed-Cal box.

What Shifter for my T56?

A T56 will come with a stock shifter from Tremec. It is left up to you as to which handle or knob you would like to put on it. However, most guys do away with the stock shifter entirely and replace it with a Steeda Tri-Ax.