1967 Ford F100 was purchased in June of 1998. It had a worn out
352 and a C-6 transmission in it. I swapped in a built 351
Cleveland backed by a C-6 with a stall converter and 9-inch
center section with a Detroit Locker and 4.11 gears. This was a
fun combination in my short bed! I pulled it off the road in May
of 2001. In my quest for more economical transportation I
decided to swap in a 1985 GT Mustang 5.0 engine and a
transmission with overdrive. I traded a big-block C-6 to my
neighbor for the 5-speed out of his 1988 F150. It was behind a
4.9L (300) straight six. Following are the things I had to do to
get this combination to work.
I used a M5R2 from a late model F150 with a 4.9L. One from a
4.9, 5.0, or 5.8 will work; they all have the same bell housing
I used a flywheel that I purchased off E-bay. It was from a 1986
F150. Make sure the balance matches your engine. 302 Fords came
balanced with either a 28.2-ounce flywheel or 50-ounce. 1982 was
the transition year between the two different balance weights.
It has to be a 164-tooth flywheel for the starter to work. The
smaller 157-tooth flywheel will not work.
The original cross member worked with the transmission mount
from my C-6. I had to move the cross member back 3 inches and
drill new holes in the frame. The transmission is shorter than
the C-6, but the mount is farther back on the transmission.
I went to the local junkyard and dug through their pile of drive
shafts. For my application, one out of a 1979 Mercury Station
Wagon with a 351W and a C-4 transmission was the correct length.
The front yoke from the C-4 will work or you can use the yoke
from the donor vehicle.
The straight six and the small-blocks use the same starter. I
got one from the local parts house. I asked for one from a 1988
F150 with a 4.9L since that’s what my transmission came out of.
I used the complete hydraulic clutch assembly from the same 1988
truck I got the transmission from. My flywheel is drilled for
both a 10 and an 11-inch clutch assembly.
I used my original 3-speed clutch pedal assembly. The stock
setup pulled up on the clutch rod. In order to use the hydraulic
clutch master cylinder it has to push towards the firewall. With
the pedal to the floor, the actuation lever on the end of the
clutch pedal should be parallel to the firewall and at a
90-degree angle to the clutch master cylinder push rod. I cut it
off with a die grinder and repositioned and welded it back on.
Make sure the bushings for the clutch pedal shaft are in good
shape. The hydraulic clutch master cylinder needs full travel
for clean clutch disengagement. Worn out bushings cause slop in
the setup, which reduces the travel of the push rod. The stock
length pushrod worked in my truck.
I mounted the clutch master cylinder next to the brake master
cylinder on the firewall. In order to mount it in the correct
position to correlate with the clutch pedal, I did the pedal
modifications first. With the clutch pedal to the floor, I used
a small carpenter's square against the firewall, I lined it up
with the bolt mounted in the end of the clutch actuation lever
and marked the firewall. I drilled a small hole through the
firewall. I used the gasket that goes between the firewall and
the clutch master cylinder as a template to make the holes
through the firewall. I had to grind a small amount off the
brake master cylinder reinforcement bracket in the engine
compartment. This is necessary so that you can screw the top off
the clutch master cylinder so that you can check the reservoir
I had to cut a fairly large hole in my floor. The shift tower
that the stick mounts to is above the transmission tunnel. The
hole is about 8 inches square. I set the engine on the mounts
with the transmission bolted to it. I jacked under the tail
housing until the shift tower touched the floor. I cut a hole
and had to trim it several times until I could lift the
transmission high enough to slide the cross member in.
been driving the truck for three years with this combination and
have made several observations. First, the transmission has a
3.75 to 1 first gear ratio. With a 4.11 ratio in the rear, it’s
a little too much gear. It feels like a “granny” low. Second
gear isn’t quite steep enough to make second gear starts without
slipping the clutch some. A 3.00 to 3.50 ratio would allow first
gear to be more useable. If you were going to do heavy towing,
then steep rear gears would be OK. Second, my Detroit Locker is
rather harsh with the manual transmission compared to the
automatic transmission that was previously in the truck. It’s
especially nasty when turning in a coasting situation with the
'M5R2' breaks down as:
R=rear wheel drive
2=2 wheel drive
The gear ratios are:
you have any questions you contact me at
DISCLAIMER: The above is what worked on my truck and is for
information purposes. Our trucks have had numerous
modifications/changes from previous owners and you need to take
this into consideration. I’m a master automotive technician with
over 20 years of experience with good fabrication and mechanical
skills. I’m not responsible for what you do to your truck!