1970-86 (521, 620 and 720-D Series) F4W63, F4W71B and FS5W71B
- Disconnect the negative battery cable.
- On 1975-86 models only, remove the shift lever from inside the cab. It is retained to the shaft rail by a C-clip, accessible under the boot. Remove the C-clip and retaining pin, then remove the lever.
- Raise the vehicle and support it with jackstands.
- On 1970-74 models, unscrew the nut securing the bottom of the shifter to the transmission shifting mechanism.
- Disconnect the exhaust pipe from the exhaust manifold. On trucks with a catalytic converter, also remove the exhaust pipe bracket next to the speedometer cable by unscrewing the two mounting bolts.
- Remove the clutch slave cylinder from the transmission case.
- Disconnect the speedometer cable from the transmission extension housing, then disengage the back-up light and transmission switch wires at the switch(es).
- Remove the bracket holding the center bearing of the driveshaft on the third crossmember of the frame.
- Remove the driveshaft(s).
NOTE: On 4wd models, this requires removal of the transfer case, which should be performed at this time.
- Support the engine with a floor jack located under the oil pan. Place a block of wood between the jack and the oil pan to prevent damage to the oil pan. Support the transmission with a jack.
- Remove the rear engine mount securing bolts and the crossmember mounting bolts. The 1970-71 models (521 series) do not have a removable crossmember; only the rear engine/transmission extension housing mount is removable from the crossmember.
- Remove the starter motor.
- Remove the bolts securing the transmission to the engine, pull the transmission toward the rear until the transmission mainshaft is free of the back of the engine.
- On 1970-71 models, place the rear of the transmission on the crossmember and then pull the transmission down toward the front of the truck and out from under the vehicle.
- On 1972-86 models, separate the transmission from the engine, then lower the transmission out from under the truck.
To install:
- Before installing the transmission, clean the mating surfaces of the engine and transmission thoroughly.
- Lightly coat the input shaft splines with grease.
- Reverse the removal procedures. Tighten the engine-to-transmission bolts to 17-20 ft. lbs. (23-27 Nm) for 1970-73 vehicles, 29-36 ft. lbs. (39-49 Nm) for 1974-76 vehicles or to 32-43 ft. lbs. (43-58 Nm) for 1977-86 vehicles.
NOTE: On the 5-speed transmission, the two bottom bolts are tightened to 7-9 ft. lbs. (9-12 Nm).
- Tighten the crossmember-to-chassis bolts to 20-27 ft. lbs. (27-37 Nm) and the clutch slave cylinder mounting bolts to 18-22 ft. lbs. (24-30 Nm). Be sure to align the marks made earlier on the U-joint and differential flange when installing the driveshaft, to maintain driveline balance.