I would like to swap the existing 3speed transmission in my 74 f100 300 6cyl for a four speed to better haul an 8'overhead camper. What will need to be changed (ie driveline, flywheel etc.) Thanks

 

I think your flywheel will be ok, but you might want a heavy duty clutch. The bellhousing should be ok. As far as the driveshaft goes, you'll need to get a shaft from a '73-'79 1/2 ton. It probably needs to be a split shaft with the splined section and carrier bearing. My New Process 435 4spd had a solid yoke for a u-joint off the back of the tranny, as opposed to a splined output shaft.

 

Henry:

I have an '81 F-100 with a 300 ci six which originally had a 4-speed where 4th was overdrive. The trans was weak and only lasted 120K miles. In 1992 it went bad and I bought a 5-speed from a wrecking yard that came from a '91 F-150 and installed it.

It used a hydraulic clutch so I had to replace some items under my dash, such as the clutch pedal rod, and convert my truck to the hydraulic clutch. It was a bitch but I love it now. Also, the 5-speed is longer so I needed the cover plate that bolts to the floor of the truck and covers the opening over the trans. I'm sure your truck is different so you will need to compare everything. The shifter is integrated into the tail of the 5-speed so you have no choice where the shifter will come up through your floor's trany hump. It worked out OK in my '81.

I believe I used the original flywheel but I needed to use the shorter driveline from the '91 truck. If you have a 2-piece drive line, and if you opt for the 5-speed, then you may need to have a custom drive line made. I just converted a '71 F-350 from its 390 to a 400M with a C6 that uses a slip-joint at the rear. I took both drive lines to a drive line shop, with accurate measurements, and they combined the two drivelines. They replaced the drive line's center bearing because you cannot have a slip joint at both ends of a drive line segment. According to them that makes that segment "happy" and you risk leaving that segment somewhere on the highway. They used a center bearing that holds onto the front shaft segment. Modified and balanced it cost me $185.

The 5-speed in my '81 is great. I don't have a granny but the first four gears are fairly close together which makes driving around town easier. I also have overdrive which helps a lot on the freeway.

Bruce