1991-1993 THUNDERBIRD/COUGAR 5.0 LITER V-8

Preparation for conversion

This manual was developed as a result of my experiences converting my 1993 Thunderbird 5.0 liter V-8 vehicle from Automatic Over Drive (AOD) to a Borg Warner T-5 5-Speed manual transmission.

There are several distinct phases of the conversion process.

Accumulation of necessary parts
General Vehicle Preparation
Dash Removal
Brake Pedal Assembly Modification
Clutch Pedal Assembly Installation
Automatic Transmission Removal
Clutch Installation
Manual Transmission Installation
Shifter Installation
Reinstallation of Dash

The major assemblies of the vehicle that will be changed or modified are:

Transmission
Clutch pedal assembly, including master cylinder
Brake pedal
Clutch, including release bearing

Note:  These instructions are intended to be used in conjunction with the Ford Thunderbird/Cougar Service Manual for your year of vehicle.  I used the Service Manual when accomplishing the conversion of my vehicle.  In numerous places within these instructions I refer to disassembly or assembly instructions within the Service Manual.  I have not repeated the steps described in the Service Manual.  I have added language to explain what I found was lacking in the Service Manual.

Service Manuals can be ordered from Helm, Incorporated, P.O. Box 07150, Detroit Michigan 48207.  The price of the Service Manual when I ordered it was $59.  The part number for the Service Manual for my 1993 Thunderbird was FPS-12196-93.  I ordered my Service Manual (as well as an Owners Guide) via telephone to Helm at 1-800-782-4356.

Note:  The Ford mechanic who assisted me in accomplishing the conversion suggested that the Electrical & Vacuum Troubleshooting Manual (EVTM) also be purchased.  It has detailed information regarding electrical and vacuum systems including all connectors.  In order to complete the conversion of my vehicle the Ford mechanic had to refer to the his dealer's copy of the EVTM.  This information was needed when converting and reconnecting the electrical connections regarding the clutch interlock on the clutch pedal and the connections to the T-5 transmission.  The part number for the EVTM for my car was FPS-12116 and the cost was $32.

Note:  The June, 1997 issue of SuperFord magazine contained an article on the conversion of a 1993 Thunderbird from the standard AOD automatic to T-5 5-speed.  This conversion was accomplished by Ed Bailes.  He accomplished the conversion by doing much more fabrication than these instructions contain.  He owns a parts company, R&E Racing, and has at his access a machine shop.  The photos in the article may be helpful.

There is also an article in the January, 1997 issue of Muscle Mustang and Fast Fords magazine which describes the conversion of a Mustang from AOD to T-5 5-Speed transmission.  It may also contain information and that is helpful in a general way.  Note however that the Mustang and Thunderbird have different bodies and many items are not interchangeable.

Accumulation of necessary parts

I strongly recommend that you collect all of the necessary parts prior to beginning this project or you will find you vehicle out of service for weeks while you order and wait for delivery of required parts.  I further suggest that you may want to purchase the parts from Dave Weaver at Five Star Ford in Scottsdale, Arizona.  He is very knowledgeable about such things and very helpful.  He is the person who very patiently helped me order the parts I needed.  In more than twenty years of tinkering on Fords I have never met a better parts man.  His telephone number is (800) 866-1520.  Also, I have provided him with a copy of the Ford parts list that accompany this manual.  Five Star Ford does not accept credit cards.  I found that getting the quote for the price from Dave Weaver and then sending a money order was the best method of paying.

Note:  These instruction were prepared using my 1993 Thunderbird.  There may be minor differences for those owners converting 1991 and 1992 models.  I believe the differences should be very few as I am unaware of significant changes in the parts of the that are being converted even though other parts of the car may have changed appearance.  Also, many of the parts used are from the 5-speed Supercoupe which also did not change much mechanically from 1989 through 1993.

In order that the correct parts are provided for your particular car, be certain to inform Dave Weaver of the model year of your particular car.  He will be able to check to determine if there are any part number differences for your 1991 or 1992 model.

General Vehicle Preparation

To prepare the car for the conversion I strongly recommend first driving it until the car is very low on fuel.  The vehicle should then be placed on four jack stands since you will need access to all areas underneath the vehicle from front to back.  Place the car sufficiently high to allow you easy access to the bottom of the car.

After placing the car on jack stands the battery should be disconnected prior to removing the dash.  Removal of the front seats that have power adjustments will be easier if the battery is connected to allow movement of the power seats for access to the seat track bolts.  Immediately after removal of the seats the battery may be disconnected.

Dash Removal

To convert the brake pedal assembly and install the clutch pedal assembly you must first remove the steering column, dash assembly and console as described in section 011-12 of the Thunderbird/Cougar Service Manual.

NOTE:  The entire removal of the dash assembly is time consuming and will take the inexperienced mechanic several hours to accomplish.  Patience and persistence are required.

Comment:  The dash assembly removal instructions are fairly accurate with the exception of step 11, which indicates the removal of one screw, where on my car (1993 Thunderbird V-8 5.0), there was one nut.

NOTE:  The removal of the dash assembly from the vehicle will be accomplished much easier if the driver's seat is removed by removing the bolts from the front and rear of each of the two seat tracks.  You must also disconnect the wiring harness from the bottom of the power seat.  This is easily accomplished if the seat track nuts are removed and the seat is tipped back to allow access to the wiring connectors.

NOTE:  A small jewelers type screw driver is very handy for use in disconnecting many of the electrical clips and connectors underneath the dash assembly.

Comment:  In my Ford Service Manual step 17 indicated removal of wiring, heater and air conditioning vacuum lines and control cables.  This amounted to a lot of work as there were many clips and connectors to remove.

Comment:  Removal of the console required removing the front portion of the console from its base in order to obtain access to several screws that required removal.

NOTE:  There is a large electrical plug on the upper left hand portion of the fire wall very near the location where the clutch pedal will be placed.  As the dash is removed a bolt needs to be removed from the bottom of that two piece plug in order to remove the dash.  Once the dash is removed the upper portion of the plug is still in the position that will interfere with the installation of the clutch pedal assembly.  In the center of the plug, on the extreme left hand side, if one observes closely, there is a tab in the center.  That tab is pressed inward toward the plug the entire plug assembly can be slid off of its white, nylon mounting bracket, so that it can be moved out of the way to allow installation of the clutch assembly.
 

NOTE:  All of the wiring connections to the dash are via some type of connector with one exception.  That exception is the coax cable and two small wires which emerge from the lower right hand portion of the kick panel near the passenger door and run upward near the bottom of the glove box.  The wires and coax cable connect to the power radio antenna.  I observed no connector on the coax cable and the two associated wires and, in fact, have verified that there is not connector closely associated by consulting with an experienced Ford mechanic.  Two options are to cut the cable and two wires at a convenient place for re-splicing, or remove the inner fender panel near the right wheel and disconnect the wire from the antenna.  My friendly Ford mechanic indicates that the latter is difficult at best and he strongly recommend cutting the wires at a convenient place below the glove box and re-splicing them upon re-assembly of the dash.

Brake Pedal Assembly Installation

The existing brake pedal must be exchanged for the brake pedal from a 5-speed Supercoupe.

NOTE:  The original brake pedal must be removed following the steps after 06-06 in the Service Manual, beginning on page 7 of that section, in my 1993 Manual.  The title of the section is "Brake Pedal Removal."  Instead of removing only the brake pedal, I found it easier to remove all three pedal support-retaining nuts as well as the upper bolt and remove the entire assembly.  Be sure to loosely place the nuts back on the studs to insure that the brake booster is not moved out of position.

NOTE:  The 5-speed Supercoupe brake pedal assembly, was thought to be an interchangeable part as an entire unit, for the automatic brake pedal assembly.  It was in fact, not interchangeable.  One of the three studs from the power brake booster did not line up with the 5-speed Supercoupe pedal bracket.  Also, the power brake booster rod was noticed to attach to the opposite side of the brake arm on the Supercoupe arm compared to the AOD brake arm and at a different height.

Note:  If your car has anti-lock brakes, then the 5-speed Supercoupe brake pedal assembly can apparently be used without modification since all Supercoupes had anti-lock brakes.  The previous statement is believed to be true although my car which was used to make these instructions did not have anti-lock brakes.

NOTE:  If the car being converted does not have anti-lock brakes (as was the case for my car), then in that event the original brake pedal assembly and 5-speed Supercoupe brake pedal assembly must be combined, in order to fabricate an assembly that will work on a non-ABS car.  The conversion is as follows:

1. The brake pedal arm needs to be removed from the 5-speed Supercoupe brake pedal assembly.

2. After removal the large pin on the driver's side of the 5-speed arm needs to be removed by grinding off the weld bead from the passenger side of the arm.

3. The pin then needs to be pressed out and reversed in direction and pressed back into the arm.

4. A weld bead then needs to be placed around the back side of the pin to secure the pin.  This will result in the pin now extending to the passenger side of the arm and the weld bead being placed on the driver's side of the arm.

5. This arm is then substituted for the existing pedal arm in the original brake pedal bracket.

6. Reinstall the brake pedal bracket in the original location on the inside of the fire wall.

Clutch Pedal Assembly

Comment:  There is no pre-existing hole for the clutch assembly to mount to the fire wall, although, the bolt holes and center of the mounting are dimpled in the fire wall.  As a result, a hole two inches in diameter needs to be cut with a hole saw and three holes need to be drilled in the fire wall to secure the mounting bolts.  Inspection will disclose three dimples in a triangular shaped pattern.  A trial fit will disclose that these dimples coincide with the pattern needed for the mounting studs of the clutch pedal b racket.  Drill each of these dimples with a drill just large enough to fit the studs on the clutch pedal bracket.  When the bracket is installed care should be taken to place large washers on the forward side of the  fire wall in order to spread the load on the thin metal of the fire wall.  I used fender washers backed by standard washers to spread the load as much as possible.

I found that cutting the center two inch diameter hole for the clutch master cylinder to be difficult.  First I had to purchase a high quality two inch diameter hole saw.  I then needed to drill a pilot hole with 1/8 th inch drill  bit.  I then used the two inch hole saw.  I found it difficult to cut the hole, but I was eventually able to cut the hole.  The drilling and cutting were of course accomplished from the inside of the car.

NOTE:  Immediately above the installation location of the clutch pedal assembly is a rounded triangular indentation in the fibrous pulp plastic-like insulation material.  A trial fit of the clutch pedal assembly will show that the upper mounting point for that clutch pedal assembly to be located in that rounded triangular indentation.  Examination will show that three small tabs of material hold the rounded triangular portion of the fibrous material.  Cut out that rounded triangular portion by severing the small tabs and remove the center portion.  Removal will disclose a hole in a reinforced plate located in the chassis, ready for the installation of the upper mounting portion of the clutch assembly.  Trial fit of the clutch pedal assembly is easily accomplished only after removal of the large, white, gray and black multi-tab electrical connector as described elsewhere.

NOTE:  Close inspection of the hole in the reinforced plate located above the clutch pedal assembly attachment point discloses that the hole is not tapped for threads and apparently needs to be tapped for ten millimeter size threads.   Measurement of the hole above the clutch mounting area indicates its diameter to be about .29 inches.  I did not have a ten millimeter tap and therefore drilled and tapped the hole for a 3/8 inch diameter bolt about one inch long.  It worked fine.

NOTE:  The clutch master cylinder mounts to the clutch pedal bracket.  It is installed by first inserting the forward end of the clutch rod (p/n E9SZ-5R537-A) into the master cylinder.  The clutch master cylinder with rod are then inserted into the clutch bracket from the engine compartment through the two inch hole that has been drilled in the fire wall.  The cylinder is secured by turning it clockwise about forty-five degrees until the reservoir tube attachment stems are pointing upward.  The upper end of the fabricated clutch fluid tube is then able to be inserted into the forward end of the master cylinder.  I suggest not inserting the small retaining pin until you are certain that you do not need to remove it since the pin is difficult to remove.
Note:  Don't forget to install the small O-ring onto the fitting that goes into the front of the clutch master cylinder.

Removal of Automatic Transmission

The original equipment AOD transmission must of course be removed.  Follow the instructions in the Ford Thunderbird/Cougar Service Manual.  The instructions are found at page 07-01-26 in my 1993 Service Manual.

Note:  Removal of the drive shaft in these cars is more difficult than normal due to the fact that it is mounted above the gas tank.  It is fairly important that the tank be nearly empty otherwise its weight will make it difficult to handle.  I found it handy to support the gas tank on two screw type jack stands with fifteen inch long pieces of 1"X4" lumber placed on top of the jack stands to spread the load.  Once the tank fasteners were loosened, I then simply carefully screwed the jack stands lower about four inches to allow the drive shaft to be pulled to the rear of the vehicle.

Important Note:  The Service Manual indicates that to remove the transmission one should leave the torque converter attached to the flex plate and slide the transmission to the rear.  I found it virtually impossible to remove the AOD transmission in this manner as the transmission input shaft was so long that when I slid the transmission rearward it contacted the floor of the vehicle.  This was the case no matter how much I tilted the engine in an attempt to gain clearance.  My friendly Ford mechanic verified that such method was very difficult.  He suggested unbolting the torque converter from the flex plate and removing the transmission and torque converter as a unit.  This system worked well.  The crankshaft must be turned with a 15/16 inch socket attached to the crankshaft damper retaining bolt.

Note:  The AOD cooler lines must be cut and removed.  Careful not to get fluid all over the floor as I did.  Attempt to drain them first.

Installation of the Clutch

Follow carefully the instructions that accompany the hydraulic clutch bearing.  Read the remainder of these instructions prior to installing the bearing.

The top fitting of the hardened nylon tube leading from the clutch master cylinder to the clutch release bearing needs to be removed from the hardened nylon tube.  This fitting needs to be attached to #4 steel braided hose.  In my case, I took both items to a local hydraulic hose specialty shop, explained what I needed and returned two hours later to find they had braised a small fitting onto the top fitting from the nylon tube and then crimped on the steel braided #4 hose.  I had measured carefully the total amount of length needed and determined that the overall length needed is thirty-four inches from end-to-end.  This was a generous measurement and may be able to be reduced by several inches.  The thirty-four inch length can best be accomplished by a twenty-two inch hose that could be used in conjunction with the existing twelve inch hose attached to the release bearing as it is delivered from McCleod Clutch.  In hindsight, such a two piece connection would allow easier disassembly of the hose, since the connection to the master cylinder is difficult to reach with a wrench.

NOTE:  The original hard nylon 5-speed Supercoupe hydraulic tube from the clutch master cylinder to the clutch release bearing cannot be used even if a proper fitting is attached to the lower end.  This was discovered on my car.  The power brake booster used on my non-ABS car interferes with the location and routing of the tube which is used on 5-speed Supercoupes.  Apparently all Supercoupes came with ABS and had a different brake boost arrangement.

NOTE:  Two standard thread 7/16 inch bolts, approximately one and one-half inches long are needed to secure the top of the clutch housing to the engine.  The original two top mounting bolts from the AOD are approximately one inch too long and bottom out prior to securing the manual transmission clutch housing.  This is because the bosses in the manual transmission clutch housing are approximately one inch shallower than the bosses molded into the original automatic housing.  These bolts should also have steel washers under them so they do not damage the aluminum clutch housing.

Transmission Installation

NOTE:  The aluminum spacer sleeve which mounts on the transmission in order to space the release bearing away from the transmission front face was discovered to be two tenths of an inch too long as received from the manufacturer.  The instructions for the release bearing indicate the only option is to return the entire bearing set and order a bolt-on bearing.  In my car the situation was remedied by having two tenths of an inch machined off the forward facing edge of the sleeve, allowing the clutch release bearing to be placed in the proper relationship to the clutch fingers as described in the instructions that came with the bearing.

NOTE:  Careful measurement of the overall length of the clutch housing to the end of the tail shaft of the transmission on both the T-5 and in the AOD indicates that the T-5 combination would just barely fit.  It did, but was a very tight fit.  The fit was so close that it crushed about half of the rubber dust seal on the rear end of the 5-speed tail housing.  Installation was possible, but was very tight.  There is only approximately 1/4 inch clearance between the tail housing on the 5-speed manual transmission to the flange on the forward yoke on the drive shaft.  Connection of the drive shaft rear yoke to the differential pinion flange was difficult, but was accomplished. Consultation with the Ford mechanic revealed that such tight clearance was allowable on the Thunderbird since there is virtually no longitudinal movement between the transmission and the differential.  After about 2,000 miles of driving adverse effect of this close fit between the tail housing and the drive shaft yoke appeared.  The rubber dust seal was damaged to the extent that transmission fluid was gradually leaking past the seal and making a mess of the undercarriage of the car.  I eventually removed the drive shaft and had it shortened one inch.  The removal of the drive shaft required lowering of the gas tank which adds to the work.  I strongly suggest having the drive shaft shortened and rebalanced by a competent shop when it is first removed from the car for the conversion.  The shortening should be accomplished by a drive shaft specialty shop which has equipment to rebalance it.  Mine was accomplished in about one hour while I waited because I called ahead and made an appointment.  It cost about $70 to have the work done.

NOTE:  The original yoke on the front of the original drive shaft is compatible with the T-5 transmission tail housing.

NOTE:  Obtain a T-5 pigtail wiring harness from Ford or a junkyard.  Recommend obtaining the pigtail from a vehicle matching the year of the transmission being installed as the connections may occasionally differ before and after 1993.

NOTE:  Remove the speed sensor from the automatic transmission.  Install the manual transmission T-5 speed sensor driven gear and install the speed sensor into the manual T-5 transmission.  This sensor originally coming on the automatic is usable on the T-5 transmission.

NOTE:  A T-5 pigtail is needed for connection of three items:

1. The Park Neutral Start interlock switch which is connected to the red and light blue and the white and pink wires;

2. The backup light switch which connects to the black with pink stripes and purple with orange stripe wires in the pigtail; and

3. The speed sensor connection which matches directly with the original speed sensor removed from the transmission and installed in the manual transmission.

NOTE:  Splice the T-5 pigtail into the original automatic transmission pigtail for both the neutral start interlock and backup light function.  The pigtail needed must be obtained from a junk yard from a 5-speed Mustang as it is part of a main the wiring loom on the Mustang and no separate pigtail is available from Ford for this conversion.  A 5-speed SuperCoupe pigtail will not work.  I tried it.

Shifter installation

Careful measurement on my car indicated that the shifter on the T-5 transmission is located four and one-half inches forward of the center of the square opening of the 5-speed Supercoupe console insert.  I measured it.  Since the shifter mechanism itself sticks up into and above the transmission tunnel, it is not possible to use the Supercoupe console insert with the standard T-5 shifter mechanism.  In fact, the T-5 shifter is located about one inch forward of the forward edge of the opening in the transmission tunnel.  The transmission cross-member and transmission mount are useable if modified.  The single hole for the liquid filled vibration absorber where it passes through the cross-member needs to be moved.  The new hole needs to be drilled one and one-quarter inches to the driver's side of the vehicle from its original location and needs to be as close to the forward edge of the cross-member as is allowed by the nut which secures the fluid filled damper to the cross-member.  Care should be taken not to puncture the damper since it costs about $50.  Also the two mounting holes on the transmission mount need to be elongated forward approximately one-half inch.  This results in an acceptable mount, however inspection will note that vertical movement of the transmission tail shaft results in a pitching motion of the cross member.

NOTE:  As a result of the shifter location being four and one-half inches too far forward it was necessary to trim approximately three and one-half inches of sheet metal from the forward edge of the opening in the transmission tunnel.  It was necessary to modify the original console insert and fabricate a custom insert to allow the shifter to be located in the new position.  This included removal of the of the ashtray from the original console insert.

NOTE:  In order to install the shift handle into the stock T-5 transmission two, eight millimeter diameter by thirty-five millimeter long standard thread bolts are required.

I chose to use a standard Mustang GT shifter knob at a price of less than $20.  A leather Supercoup knob is available listing for about $90.  Ford Motorsport also offers a leather knob which may work.

Re-installation of Dash Assembly

NOTE:  Remove automatic transmission start - park, neutral mechanical interlock cable and bracket from the side of the steering column when re-installing the steering column.  This item extends from the steering column underneath the dash and down to the AOD shifter.  It is not needed on the manual transmission.

NOTE:  On the large box shaped, multi-pin connector located just to the left side of clutch bracket, move the small attached connector one position forward on the large connector.  Moving this small attached connector one slot forward will allow it to remain in its nearly original position without interfering with the clutch bracket.

NOTE:  The original AOD wiring harness has the six-pin clutch connector with a black jumper plug installed.  This is very good fortune since without this connector a significant amount of new wiring would need to be installed.  During the reinstallation of the dash this six-pin connector needs to have the jumper plug removed and the connector plugged in to the matching portion of the clutch interlock switch which is attached to the clutch bracket assembly.  See pages 10-03-2, 6, 7 and 9 in the Service Manual.

--Pins 1 and 2 on the clutch switch connector are normally open and close at the bottom of the clutch pedal travel.  On the 5-speed Supercoupes (and on Mustangs) these pins prevent the car from being started unless the clutch is depressed.  I discussed this safety feature with my friendly Ford mechanic.  He indicated he has always been somewhat concerned about this feature since it forces the car to be started with all of the clutch pressure on the crankshaft thrust bearing prior to there being any oil pressure to the thrust bearing.  I decided to disable the feature by shorting the two wires leading to these pins.  This will allow the car to be started without the need to depress the clutch.  To insure that the car cannot be started while in gear be certain to connect the transmission-ignition interlock switch so that the manual transmission must be in neutral in order for the car to be started.

--Pins 3 and 4 on the clutch switch connector are normally closed and open at the beginning of the clutch pedal travel.  The pins connect to the speed control (cruise control).  It disengages the cruise control momentarily when the clutch is depressed when the driver is shifting to prevent the cruise controller from increasing engine speed attempting to maintain vehicle speed during shifting.  This function becomes operational due to the good fortune of having the clutch interlock built into the existing wiring on the car.

--Pins 5 and 6 on the clutch switch connector are normally open and close at the beginning of the clutch pedal travel.  The pins connect to the multiport fuel injection computer.  I am not certain exactly what it does.  This function also becomes operational due to the good fortune of having the clutch interlock built into the existing wiring on the car.

NOTE:  The antenna and antenna power wires must be re-connected by soldering or crimp connectors at the time the dash is reinstalled.

NOTE:  In order to re-install the console base, you must remove a portion of the cross-brace on that console base which will interfere with the T-5 manual transmission shifter.

NOTE:  When re-installing the console base, you may remove the automatic transmission shifter light located with the console base as it will not be needed with the manual transmission.

NOTE:  When re-installing the console base, fabricate and install a metal cover for the rear portion of the original shifter hole in the transmission tunnel.  I suggest using aluminum or steel sheet approximately 16 or 18 gauge thick.  I used aluminum but recently found that the new Sear Hardware store had steel sheet and including stainless steel sheet that would have worked perfectly.  I initially used thin sheet aluminum that I obtained from a home hardware store.  The thin aluminum was intended to be used for flashing.  I found that the thin aluminum was not appropriate because it not only allowed too much sound through it, but also flexed and made sound itself.  Secure the fabricated cover every one and one-half inches with short sheet metal screws.  It may be desirable to install more than one layer with sound deadening insulation between the layers in order to provide the quietest ride possible in the interior of the car.

NOTE:  You may desire to have the shifter handle modified to slightly lengthen it and reshape it.  The reason for this is that by using the stock Mustang shift handle the knob is located about two inches forward of the normal location on a Mustang.  I have not found it to be a problem.  It clears the dash in all gears and even shifting to fifth gear is no problem.  However, I may purchase an after market shifter in the future.  If I do I will have it lengthened and reshaped to place it one or two inches to the rear of the unmodified location.

Testing

NOTE:  When the vehicle is driven after the battery has been disconnected the EEC IV computer will need to "relearn" some of the operating parameters.  I noticed a distinct drop in engine performance especially in responsiveness the first time I drove the car after reconnecting the battery.  My immediate reaction was that perhaps I had made a big mistake in attempting the conversion.  However, during the next day I drove the car for about an hour.  By the end of the hour the car was behaving like its old self plus I had the flexibility of the new transmission.  Since the conversion I have really enjoyed my Thunderbird much more than when I had the AOD.  The engine seems to be much stronger even without any other change.

T-5  Transmission

The major issues regarding the transmission are the decisions of (1) which version of the transmission to use and (2) whether or not to purchase a new, rebuilt or used transmission.

Versions
The two major versions of the T-5 transmission are the models that have a 2.95 first gear and the models that have a 3.35 first gear ratio.

The 1983-84 version of the T-5 had a 2.95 first gear, 1.94 second gear, 1.34 third gear, 1.0 fourth gear and .73 fifth gear ratio.  It had a torque capacity rating of 265 lbs-ft.  It is the least desirable of the various versions.

The 1985-89 upgrade included tapered roller bearings on the countershaft and caged needle bearings under the first, second and third gears on the main shaft.  It also had double synchronizers on first and second gears and steel blocker rings with friction linings on third and fourth gears.  It has gear ratios of 3.35 first gear, 1.93 second gear, 1.29 third  gear, 1.0 fourth gear and .68 fifth gear.  It had a torque capacity rating of 265 lbs-ft.

The 1990-92 version of the T-5 was upgraded further with 4615 alloy steel for the cluster and third gear and 4620 alloy steel for second gear.  A coarser pitch on second and third gears improved strength in this previously weak area.  The upgrades increased the torque capacity to 300 lbs-ft while maintaining the 3.35 first gear ratio.  A "super alloy" gear set can be used to upgrade 1985-89 model to the 300 lbs-ft capacity of the 1990-92 models.

The 1993 Cobra version of the T-5 had a stronger tapered roller bearing to replace the standard needle bearings between the input and mainshaft.  Torque capacity was increased to 310 lbs-ft while maintaining the 3.35 first gear ratio.

Ford Motorsport sells a version of the 1993 Cobra T-5, but substitutes 2.95 first gear and .63 fifth gear as part number M-7003-Z, commonly called the "Z-spec" T-5.  The taller first gear increases the torque capacity to 330 lbs-ft, the highest rated torque capacity of any T-5 sold.  This unit also includes an upgraded steel input bearing retainer.

A fully upgraded 1993 Cobra T-5 with steel input bearing retainer is sold by D&D Performance for $999 at the time of writing of these instruction.  This transmission has the highest rated torque capacity (310 lbs-ft) of any T-5 manufactured with the 3.35 first gear.  D&D also sells the Motorsport Z-spec T-5 for $999 at the time of writing of these instruction.

Several companies sell kits to upgrade the torque capacity of 1983-92 T-5 models.  Some of the same companies will rebuild a customer T-5 to upgraded specifications.

Which model to choose?

After you decide whether to buy a new or used transmission, the next choice is whether to purchase a 2.95 or 3.35 first gear ratio unit.  I chose the 3.35 first gear unit due to the weight of the Thunderbird.  All late model Mustangs come with 3.35 first gear ratio T-5 transmissions.  These late model Mustangs all weigh 300-400 lbs less than the Thunderbird.  If the Mustangs need the 3.35 first gear, then I figured our heavier Thunderbirds certainly did.  The only minor trade off compared to the 2.95 first gear T-5 is the very slightly higher highway cruise RPM, usually about 120-170 higher RPM depending on rear end ratio.  This is due to the 3.35 first gear units having a .68 fifth gear and the 2.95 first gear (Motorsport) units having a .63 fifth gear.

Speedometer
Most models of the T-5 came with a seven tooth speedometer drive gear.  That number of teeth is common with the AOD and therefore a speedometer driven gear with the same number of teeth as the one that was originally on your car is the one to choose.  However, some late model T-5 transmissions have an eight tooth drive gear.  The 1996 Ford Motorsport catalog in footnote (3) on page 98 indicates that the 8 tooth drive gears came on all production T-5 transmissions since 1990.  The T-5 that I purchased did.  As a result of the 8 tooth drive gear the speedometer will read about 15% fast at all speeds.  There are three solutions to this problem.  (1) Be certain to purchase a transmission with a seven tooth drive gear.  (2) Have the eight tooth drive gear changed to a seven tooth drive gear.  D&D Performance quoted $15 as the cost of a seven tooth drive gear.  (3)  Purchase a driven gear that has about 15% more teeth than the original gear.  Ford sells 19, 20 and 21 teeth gears.  A 23 tooth gear is available from other suppliers, but it is known to have a limited live due to its thin teeth and partial misalignment.

My experience
My car has a 3.55 rear end ratio.  This rear end ratio is recommended by many of the Mustang magazines as the best compromise for all around performance for Mustangs.  My experience indicates that the 3.35 first gear T-5 is perfect for general driving with the 3.55 rear end gears.  However, 65 mph cruise ends up being exactly at 2000 RPM (with my 25.7 inch diameter rear tires) where there is an inherent and annoying resonance in the Thunderbird (and Mustang) exhaust system.  The sound destroys some of the wonderful quiet of our cars.  If you do mainly highway driving I would recommend staying with the 3.08 original rear end ratio and the 3.35 first gear ratio T-5.  The result should be a 65 mph cruise RPM of 1650 to 1750 RPM (depending on rear tire diameter) which is below the exhaust resonance RPM.  You should also get slightly better gas milage than my 23 to 26 mpg highway milage.

Conversion Parts List

Common Parts

Approx.
List

Brake Pedal Assembly  F3SZ-2455-B  $ 55

Clutch Pedal Assembly  E9SZ-7B633-A  $168

Clutch Master Cylinder  E9SZ-7A543-A  $ 96

Clutch Reservoir   E9SZ-7K500-A  $ 29

*Clutch Fluid Tube   E9SZ-7A512-A  $ 61
(needed to obtain fitting from top of tube)

T-5 Parts

Approx.
List

Transmission: T-5 manual       $999

Clutch Release Bearing Assembly (non-Ford part)    $324

Clutch Housing    E3ZZ-6392-A   $203

Engine Plate     D9ZZ-7007-A  $ 35

Pilot Bearing     D4DZ-7600-A  $  8

Shifter Handle     E7ZZ-7210-A   $ 42

Shifter Knob(Mustang)   F4ZZ-7213-A   $ 19

Shifter Weather Seal    F9SZ-7277-C   $ 15

Shifter Leather Boot    E9SZ-7277-B   $119
M-7277-A   $ 94

Speedometer Gear(19 Tooth)  C1DZ-17271-A (Pink) $ 10

Speedometer Gear(20 Tooth)  C1DZ-17271-A (Black)  $10

Speedometer Gear(21 Tooth)  C40Z-17271-A (Red)  $ 10

Speedometer Gear(23 Tooth)  (non-Ford part)  $ 15

Flywheel     M-6375-   $ 50-150

Clutch Pressure Plate    M-7563-   $ 50-200

Clutch Disk     M-7550-   $ 50-200

List of Modified or Fabricated Parts

Brake Pedal Assembly  F3SZ-2455-B   $ 55

Clutch Fluid Tube   Have fabricate by a local hose shop using fitting from E9SZ-7A512-A.

Transmission Pigtail   From 5-speed Mustang

Clutch Release Bearing Spacer Have shortened.

Transmission Tunnel Cover Plate Fabricate from sheet metal

List of Additional Small Parts Needed

Two standard thread 7/16 inch bolts, approximately one and one-half inches long to secure the top of the clutch housing to the engine.  The original two top mounting bolts from the AOD are approximately one inch too long and bottom out prior to securing the clutch housing.  These should also have steel washers under them so they do not damage the aluminum clutch housing.

Four, twelve millimeter metric bolts forty millimeters long course thread used to secure the transmission to the bell housing.  These should also use hardened steel washers to prevent damage to the aluminum case of the transmission.

Two, eight millimeter diameter by thirty-five millimeter long standard thread bolts are required.

One, 3/8 inch bolt one inch long to secure the top of the clutch pedal bracket.  Note:  A hole needs to be tapped for this bolt.
 

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