I began searching for an overdrive alternative to the C4
transmission in my 73 mustang when my C4 transmission stopped
shifting to third gear regularly. I decided that I wanted to go with
a manual transmission due to the relative ease of repair and rebuild
of manual transmissions compared to automatics. My first choice was
the T5 transmission installed in a number of Ford vehicles from 1986
to 1996. Torque ratings for the T5 ranged from 265 to 310 ft/lbs
over the years and these transmissions were placed behind both 4 and
8 cylinder engines. The most desirable of the T5s are those from the
90 to 93 Mustang GTs and Mustang Cobras. After extensive research
and some simple math calculations I decided against installing a T5
transmission into my 73 mustang because of the high amount of torque
produced by my engine.
I decided to go
with a Tremec 3550 transmission. The Tremec 3550 weighs 100 lbs.
Although the Tremec 3550 uses a
different bellhousing and is larger
transmission it is a direct replacement for the T5 transmission. The
Tremec 3550 has a 350 ft/lbs torque
rating. There is also a heavy duty version of the Tremec 3550 called
a Tremec TKO with a torque rating of 400 ft/lbs.
Input spline count
Output spline count
spent a month searching the internet looking for a tremec
transmission. I found one on ebay and got it for 800 dollars. There
are a number of companies that sell these transmissions new or
rebuilt. I would recommend that you buy a new or rebuilt tremec to
insure that you get one in proper working order. I also purchased a
used bellhousing and flywheel.
Transmission Sales and Service
Tremec 3550 ($800.00)
Tremec Shifter (Free with
- Flywheel (came with
bellhousing had it balanced to match
- Flywheel Bolts ($20.00)
- Driveshaft Yoke (I used
the one from my C4)
- Clutch Pedal (Came with
Clutch Pedal Assymboly $100)
- Clutch fork ($20.00)
Throwout Bearing (Included with Clutch
- Clutch and Pressure
Plate ($195 for the first one, $175 for the second)
- Pressure Plate Bolts
Crossmember (Modified my C4
- Two 3/8 8” grade 8 bolt
(15.00) with locking nuts and washers
- Two 3” pieces of 1”
Tranny Fluid ($6.00)
- Shifter Boot ($3.00 from
actual transmission swap took me a month and a half to complete.
Most of that time was just down time for my car while I got parts
and money collected. I would say that I spent 30 hours working on
installing the tremec. Then I spent another 40 hours messing with
constructing a clutch actuation system (it was a major pain). The
only other part that gave me some worries was locating a
crossmember for my application. There
are a number of companies who sell crossmembers
and whole T5/Tremec swap kits for early
mustangs, unfortunately none of them sells a kit for 71-73
mustangs. I moved forward with the transmission swap and figured I
would fabricate one (rig one up) after I had the
Tremec in place. Luckily, before I got
that far in the swap, I stumbled across a website where a guy doing
a T5 swap in a mustang II modified his old
crossmember and used it to mount the T5. After doing some
measurements I discovered that I could also modify my old
crossmember to mount the
Tremec in my mustang.
For more info check out these links:
Disconnected the negative battery cable
and then raised my mustang up and placed it on jack stands.
up in the air
Disconnected the driveshaft and removed
Removed the starter and transmission
Disconnected hydraulic and vacuum lines
from the C4
Removed the torque converter nuts
Placed a jack under the C4 and then
removed the bolts in the bellhousing
Removed the C4
Removed U joints from the driveshaft
Trip to the
Machine and driveshaft shop to…
Have drive shaft shortened ¾ in and
Have flywheel machined so that it
and my automatic flexplate have the same balance ($40.00)
I intended to also have my used flywheel resurfaced but the
machinist said that my flywheel didn’t need it.
and Bellhousing installation
installing the clutch and pressure plate to the flywheel be sure to
check that the clutch disk gear matches
the spline count on the input shaft and that the disk
fits onto the transmission input shaft.
With Clutch fork inside
Flywheel, Clutch, Pressure Plate Pilot
Bearing and Flywheel Bolts
- Installed the Pilot Bearing into the
end of the crank
- Put the backing/index plate up to
- Installed the flywheel onto the
crank and torqued the flywheel bolts to 75 ft/lbs
- Cleaned the flywheel surface and
pressure plate surface of oil using brake cleaner
- Placed the clutch disk inside the
pressure plate with the correct side of the disk facing out
- Using an alignment tool to center
the clutch disk to the pilot bearing I drew the pressure plate
to the flywheel evenly using the six pressure plate bolts. Once
the pressure plate was against the flywheel I torqued the six
pressure plate retaining bolts to 24 ft/lbs in a star pattern.
- Installed the throwout bearing on
the clutch fork (it slips off the fork very easily)
- greased the bellhousing pivot ball
and installed the clutch fork in the bellhousing
- Installed the tremec bellhousing but
did not tighten it down to the engine block
Note: It is easier to
work the transmission around in the transmission tunnel if you
remove the shifter. Just be sure to reinstall the shifter threw the
shifter hole in the transmission tunnel before you move the
transmission to far forward.
- Put in 3 quarts of
Syncro Mesh transmission fluid into the transmission and
checked the fill level
Note: I could have filled the
Transmission through the shifter later and missed out on getting to
see what Syncro Mesh taste like.
- Placed C4 transmission yoke into the
tremec to keep fluid from leaking out
- Placed the tremec on a jack with the
help of a friend
- Jacked the tremec up began moving it
towards the bellhousing.
- knocked the throwout bearing off the
clutch fork with the input shaft as I brought the transmission
into the bell housing
- pushed the tremec away from the bell
housing and reinstalled the throwout bearing on the clutch fork
- repeated steps 5 and 6
- Got the input shaft threw the
throwout bearing and brought the tremec within 4 inches of the
- wrestled with tremec for an hour
repeating steps 5-8
Note: Steps 10-27 are
not necessary if you check to make sure the clutch disk gear
matches the tremec’s input shaft
- Backed the bellhousing far enough
away from the block to allow the bolts that hold the tremec to
the bellhousing to be started
- Insured the tremec was meshing with
the gear in the clutch disk by turning the transmission yoke and
feeling for meshing of the gear and input shaft
- Tightened down the bellhousing
- Heard a metallic popping (clutch
disk being broken)
- Tightened down the transmission
- Installed modified C4
- Connected Neutral Safety switch in
line with the ignition switch so that the engine will not start
- Reconnected the driveshaft with new
- Once the hydraulic clutch actuation
system was working, discovered that the clutch was not
connecting the engine to the transmission
- Disconnected the drive shaft, and
nutral safety switch
- Moved the
tremec back away from the
bellhousing and left it on a jack
- Removed the shifter from the
tremec to allow me to move the
transmission back farther away from the
- Removed the bellhousing, pressure
plate and clutch disk
- Discovered that the gear in the
clutch disk was crushed by the tremec’s input shaft
- Got a new clutch disk and pressure
- Checked to see that the clutch disk
gear and input shaft matched
- Repeated Flywheel, Clutch and
Bellhousing installation steps 4-9
Clutch Disk: The gear in the center is pushed out and cracked
- Repeated Tremec
installation steps 5-8
- Wiggled the tremec close enough to
start a bolt into the bellhousing
- Wiggled the tremec some more and
noticed that it had moved closer to the bellhousing
- Started the rest of the bolts into
- Reinstalled the shifter on the
tremec through the shifter hole in my car
- wiggled the tremec and finger
tightened the bolts holding it to the bellhousing
- Once the tremec was against the
bellhousing I tightened all the tremec and bellhousing bolts.
- Reinstalled modified C4
Modified Crossmember: The bolt is an 8”
grade 8 3/8 bolt with a locking nut. To use my old
crossmember I simply had to cut off the
lip from one side and move it to the outside rear of its original
- Reconnected Neutral Safety switch
- Reconnected the driveshaft with new
- Went for a drive
Clutch Pedal installation
Since my car originally was an automatic I had to find a clutch
pedal assembly to add to my mustang. The assembly was not hard to
find but it was expensive. After I got the assembly I compared the
clutch pedal assembly with the automatic pedal assembly in my car
and I realized that I did not need the entire assembly just the
clutch pedal itself. There is a hole in the automatic pedal assembly
for a clutch pedal in my mustang but it was missing the bushing that
the pedal rides in. A clip at one end of the clutch pedal holds it
in place in the assembly.
Clutch pedal assembly with clutch
pedal removed. The grey bushing can be seen and is where the clutch
pedal rides in the assembly.
measured the distance from the end of one bushing to the other and
took the clutch pedal to the hardware store. There I found a piece
of pipe of the appropriate length that was threaded at each end and
large enough in diameter for the shaft on the clutch pedal fit into.
I also found plastic washers to ride on the clutch pedal shaft
inside the pipe and a pair of nuts to hold the pipe in the automatic
Clutch Pedal with plastic
bushings installed, Pipe, nuts and an extra bushing.
Automatic Brake Pedal next to the
Manal Brake Pedal: Notice that the pivot
points are in different locations
In order to install the clutch pedal I had to remove and shorten the
automatic brake pedal. The manual brake pedal that came with the
clutch pedal assembly could not be used in the automatic pedal
assembly because of where its pivot point is located.
Clutch Pedal installed with shortened
Hydraulic Clutch Actuation System
After installing a Tremec 3550 in
my mustang I needed to construct some type of clutch actuation
system. My initial ideas involved the use of a clutch cable.
Unfortunately the mechanical linkage I constructed to connect the
clutch pedal to the cable was not strong enough to handle the forces
involved in actuating the clutch.
Clutch Pedal with soon to fail clutch
cable bracket, a very bad design.
All my attempts to
improve the linkage failed so I decided to try a hydraulic set up
that I had seen on a post at
The hydraulic clutch system that I constructed is basically the same
as deatman68’s. It uses the same master and slave cylinders as the
deathman and the system works
Here is a link to
The major parts that I needed were in a list I found on
another post by deathman68. I ordered the Adjustable pushrod,
Master, and slave Cylinders from Mckenzies at
The rest of the parts I picked up at
local hardware and auto parts stores. I omitted item 4 from the
parts list and used a ¼ inch thick 36x2 inch strip of steel I had
previously purchased to construct a bracket for attaching my slave
cylinder to the tremec. I also omitted item 19. Item 15 is a remote
reservoir and I found one of those at my local junk yard on a 90
Ford Ranger. I also got the hose that attached the reservoir to the
brake master cylinder on the ranger. I had some difficulty finding
parts 13 and 14. They are the fittings for the master and slave
cylinders. I suggest that you take the cylinders with you and go to
a plumbing or farmer’s supply store to find all the fittings you
need. Be sure to get a fitting with a 90 degree angle for the slave
As far as tools go
you will need to get cutting bending and flaring tools so that you
can route the brake line from the master cylinder to the slave
cylinder. These tools are all inexpensive and you will be surprised
at how easy they are to use.
Item Part No. Price
1)Master Cylinder 3/4 Steel CNC 711-3/4 62.95
2)Push Style Slave Cylinder 7/8 CNC 305-B 51.00
3)Adjustable Pushrod (Slave) CNC 1312 13.99
4)1/4" Plate Steel 9"x9" 11.99
5)2 ft 5/16" fuel Hose 5/16" SAE30R6 4.23
6)2-5/16"x1" bolts (for reservoir) 1.50
7)6-3/8"x1" bolts (for master,slave,and bracket) 4.75
8)2-5/16" crush washers 0.20
9)2-5/16" nuts 0.34
10)6-3/8" crush washers 0.90
11)6-3/8" nuts 1.75
12)3 ft. 3/16" ID rigid fuel line 2.99
13)1/8" to 1/4" hose barb 1/4H1/8MP 1.29
14)1/8" reverse flare fitting 0.99
15)Remote reservoir 2.18
16)1-5/16"-24 (fine thread)bolt 4" long 1.00
17)Coupler nut (5/16"-24 fine thread) 2.30
18)Bronze Bushing (1/2" OD 3/8" ID) 2.30
19)Clevis Pin 0.45
TOTAL COST: $166.74
1- Remote clutch master cylinder
reservoir from a 90 ford ranger
1- 1 ft 3/8” fuel hose
1- 1/4” thick 36”x2” Steel strip
1- 36” long 1” square steel tube
6- ¼” x 1” bolts
6- ¼” x 2” bolts
12- ¼” nuts
12- ¼” washers
2- 5/16”-24(fine thread) nuts
Dot 3 Brake fluid
Thread lock (for the pipe fittings to
keep fluid from leaking)
Tube flare tool
Tube bending tool
System Installation Steps
Note: I installed all
of the pipe fittings into the slave and master cylinders using
thread lock to ensure they would not leak before placing them on the
car. If you do so keep in mind that you may have to make adjustments
to the angled fitting on the slave cylinder after you have routed
brake line to it.
Find a suitable location on your
firewall for the master cylinder.
Drill a hole large enough for the master
cylinder at that location on my 73 mustang I removed what I think is
an original ground wire that ran through the fire wall and reran it
through a hole on the right side of the steering column. The hole
for the wire and grommet required only slight enlargement to
accommodate the master cylinder.
shows the location of the grommet and wire under the dash
Use the master cylinder as a template
and drill holes for the ¼” master cylinder mounting bolts in the
Find or make metal plates to go inside
the car between the bolt heads and the fire wall for reinforcement.
I used a couple of 1/8 steel brackets I had lying around.
Mount the Master cylinder to the
Cylnder mounted on the firewall
Measure the distance from the clutch
pedal arm to the master cylinder pushrod.
Remove the clutch pedal, fabricate and
attach an arm for actuating the pushrod. I constructed an arm using
a 10” piece of the ¼” thick steel strip. I added a 3” piece of ¾”
square tubing to the arm. I would later drill a hole in one face of
the tube where it meets the pushrod.
Pedal with arm installed
Note: The diagram
below shows what the arm looks like and how it attaches to the
pushrod. The hole in the metal tube is only in one side the other is
closed so that the rod does not pass threw.
A better design
would incorporate some type of pivot ball that attaches to the
pushrod and attachment arm. Below is a picture of what the improved
design might look like.
Reinstall the clutch pedal with the
actuation arm installed.
Mark the square tube on the arm at the
point where it meets the pushrod. You may need to lengthen the
pushrod by attaching the 5/16-24 (fine thread) bolt with the coupler
nut so you can make this measurement.
Remove the clutch
pedal and drill a hole in the face of the tube where you marked it
would meet the pushrod.
Reinstall the clutch pedal with the arm.
Place the end of the bolt, which you
will have to cut the head off of, into the tube on the actuation
Pedal Actiation Arm Attached to Master
Note: As the clutch
pedal is pushed in the actuation arm pushes the pushrod into the
master cylinder. Since the arm travels in an arch the push rod
travels up and down in an angle. In order to insure that the pushrod
wouldn’t bind on the walls of the master cylinder as it is pushed in
at an angle. I ensured that the pushrod would be initially angled
down below the master cylinder’s center line. As the clutch pedal is
pushed to the floor the pushrod is forced to angle upward by the
arm. At the end of the clutch pedals travel the pushrod is angled
upward above the master cylinder’s center line.
Fabricate a bracket to attach the slave
cylinder to the tremec transmission.
Note: I will add
measurements and a diagram of my bracket later. It was constructed
from the ¼ inch steel strip.
Attach the slave cylinder pushrod to the
clutch fork. You will have to readjust it later to get the correct
clutch engaugement and
disengagment points along the clutch
Determine the route that the brake line
will follow from the master to the slave cylinder.
Make a diagram of the brake line’s
layout with measurements and approx angles.
Make your bends in your line and
do a test fit in the car.
Attach the brake line to the master
cylinder then make adjustments to the route, and bends in the line.
Determine the final distance and bends
to the slave cylinder. Once you are satisfied cut the line the
appropriate length and hookup the end to the slave cylinder.
Install the brake reservoir in an
appropriate place on the fender well or firewall.
Attach a hose from the reservoir to the
Fill the reservoir with brake fluid.
Locate the bleeder on the slave cylinder
and get a friend to assist you in bleeding the air out of the line
having them press the clutch pedal in while you open the bleeder
screw and watch for air bubbles. Closing the screw before they let
off the pedal. Be sure to add brake fluid to the clutch reservoir
during the bleeding process so that you do not run the master
cylinder out of fluid.
Test the system and watch for leaks.
Adjust the Slave Cylinder pushrod so
that the clutch fork engages after the pedal has been pushed in 1¼
inches from its initial position. Then be sure to check that
pressing the pedal all the way to the floor does not overextend the
clutch fork and bend the fingers that release the clutch inside the
Tests drive the car and readjust the
clutch engagement if necessary.