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You are here: Home Tech Articles & Tutorials Engine/Transmission M5R2 5-Speed Transmission Swap Into 67-72 F100
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M5R2 5-Speed Transmission Swap Into 67-72 F100

by Kevin Ames (SVT22)

My 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 bolt pattern.

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.

Cross Member
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.

Drive Shaft
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.

Clutch Pedal
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.

Master Cylinder
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 level.

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.

I’ve 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 clutch disengaged!

'M5R2' breaks down as:
R=rear wheel drive
2=2 wheel drive

The gear ratios are:
First 3.75
Second 2.32
Third 1.43
Fourth 1.00
Fifth 0.75

If 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!


You are here: Home Tech Articles & Tutorials Engine/Transmission M5R2 5-Speed Transmission Swap Into 67-72 F100

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