Swapping a 5-speed into an F-100

Driving a classic truck is fun. It’s even more fun with a stick.

American Powertrain had an F-100 project built by their IT guy Barry. It’s a “pro-touring” like project he has been slowly and meticulously building at home. The truck has good handling and old school looks with a modern EFI 351W under the hood. The parts are a go-to play list for F-100 builds: Panther front end swap, FITech and disc brakes. He knew the final cherry on top would be a TREMEC TKO 5-speed swap. Follow along on the install.

Barry’s 1972 F-100 short bed. 351W with Fitech EFI, Trick Flow heads and mild cam. Even has Vintage Air

The truck came in with no transmission so this gave us a nice clean place to start. The Crown Vic Panther front end swap puts the engine pretty close to stock location so transmission placement was no issue.

The heart of it all is the American Powertrain F-100 Pro-Fit 5-speed kit, using a TREMEC TKO-600. This kit has everything you need to install a 5-speed in a classic Ford truck: crossmember, hydraulic clutch, pressure plate clutch, bell and flywheel.  A custom built driveshaft is also included in the kit. Once you do the install, fill out the driveshaft order form to send in the measurements and your new, custom made shaft will be on its way a couple of days.

The first thing we did was slap the bell housing on with no flywheel or clutch. We hoisted up the trans to see what kind of clearances we had to work with on the tunnel. Turns out we had to do a little hammering just at the vent tube (a common clearance issue on TKO’s). One of the ways American Powertrain gets these larger transmissions to fit into older cars is case minimizing on the transmission. They also offer a fiberglass tunnel hump for F-100. 6-speeds will need a larger tunnel opening.

The trans on the left is a stock out of the box TREMEC TKO. The trans on the right has been “minimized” by American Powertrain. You can see the corners on the top cover of the trans were CNC milled and new cover plates installed for better tunnel clearance. Doing these mods yourself will void the TREMEC warranty. APT works with TREMEC on approving these mods and offers a two-year warranty. The shifter has been replaced with a White Lightning short throw shifter that also serves as forward shift position to clear a bench seat.

Once the tunnel clearance’s was checked and shifter location set up, we installed the X-Factor universal adjustable crossmember. American Powertrain has these in 3 sizes that adjust to fit frame widths from 20” to 34”. We used the widest one that adjusts from 32”-34”. This allows you to set height for the right driveline angle, and uses a standard GM transmission isolator. The crossmember also allows adequate exhaust clearance for lowered trucks. Simply slide the plates to the frame, mark your holes and drill, using the supplied grade 8 hardware

Set the crossmember to the right driveline angle. Plus or minus 3 degrees are the specs that TREMEC calls for to avoid vibration.  A cheap angle finder makes this pretty easy.

Now the real fun begins.  Once we did the mock up and took out the trans, it was time to start the install. One of the critical procedures is to dial indicate your bell housing. This is very important to make sure the bell is centered on the engine so the input shaft lines up straight with the crank. This is critical for transmission longevity. American Powertrain has videos and instructions on how to get this right. 

Once the bell is checked, take it off and start installing the flywheel and clutch. Make sure to torque everything down to spec!

Now its time for more math! This time it’s for the hydraulic clutch bearing. Once the bell and clutch were installed, we had to measure the distance from the pressure plate fingers to the back of the bell. Then from the face of the trans to the face of the bearing. This difference tells us how far the bearing is sitting back from the clutch fingers.

The Hydramax Hydraulic Clutch Kit allows many different clutch combinations. The key to this is making some measurements and setting the depth correctly for the set up you have. The specs are .150” air gap between the bearing and the pressure plate fingers. Once you get the measurements this will determine the number of shims you need to set it correctly for long clutch and bearing life. Once again, American Powertrain has all the instructions and videos to make this pretty easy.  A digital caliper is all you need.

Install the trans and the bearing together. Make sure to run your lines out of the bell and away from the exhaust.

Barry’s truck already had a clutch pedal. These are fairly easy to find for Fords in a junk yard or any of the restoration catalogs.

Next up mount the patented Hydramax master cylinder bracket on the fire wall. This requires a about four holes to be drilled. The bracket has a backing plate to prevent firewall flex. You may have to drill an additional hole higher up on the pedal to get the clutch rod ratio set correctly. We had to lengthen out the mounting point using a piece of flat stock to get the correct angle. American Powertrain will have this added in to the kit for F-100’s.

Finished install is now ready for a new drive shaft. Do a few simple measurements on the included driveshaft measurement form then send it in to American Powertrain. In a couple of days your new driveshaft will show up, ready to install.

We had plenty of room for a bench seat with a double bend 18” shifter handle. APT has tons of shifter handles, shifter knobs and boots to finish up your install. We finished it off with one of their gunmetal gray billet shift knobs to match the wheels of the truck. No more boring automatic!

American Powertrain also now offers an F-100 fiberglass high hump tunnel replacement for F-100s. TKOs and T-5s fit the truck with slight massaging. Magnum 6-speeds will need more clearance. But if you want all the room you can get grab one of these to finish it out.