Models through 1972 use a Thompson-type power cylinder system to turn a conventional steering gear. The steering gear application is the same as for trucks with manual steering, and gear removal is the same as with manual steering.
1973-88 models use a type 708 integral power steering gear.
No adjustments are possible on the Thompson-type power cylinder system.Preliminary Checks
- Remove the gear from the truck.
- Rotate the gear several times through its travel to expel all fluid from the gear.
- Place a 3 / 4 in. (19mm) 12-point socket on the stub shaft. Using an inch pound torque wrench, check the torque 1 / 2 turn off the right stop, then 1 / 4 turn off the left stop. Record these figures.
- Center the gear and check the torque 1 / 2 turn to each side of center. Record these figures.
- Turn the gear 90° to the right of center and turn the gear in a 180° arc to the left of center. Record the reading.
- Remove the adjuster plug locknut.
- Turn the adjuster plug in until the plug and thrust bearing are fully bottomed. This takes about 20 ft. lbs. (27 Nm) of torque.
- Matchmark the housing and one of the holes in the plug.
- Measure counterclockwise 1 / 4 in. (6mm) from that mark and make another mark on the housing.
- Rotate the plug counterclockwise until the marked hole aligns with the second housing mark.
- Install the locknut and, while holding the adjuster plug, tighten the locknut securely.
Using an inch pound torque wrench on the stub shaft, turn the shaft to the right stop, then back
turn. Note the reading. The reading should be 4-10 inch lbs. (0.44-1.1Nm). If not:
- Loosen the sector shaft preload adjuster screw locknut and turn the screw 1 1 / 2 turns counterclockwise. If the screw bottoms, turn it back 1 / 2 turn.
- Retighten the locknut while holding the screw.
- Loosen the adjuster plug locknut.
- Turn the plug 1 turn counterclockwise.
- Turn the stub shaft to the right stop, then back 1 / 4 turn. Record the torque reading.
- Bottom the adjuster plug firmly with 20 ft. lbs. (27 Nm) torque, then back it off until the stub shaft rotational torque is 3-4 inch lbs. (0.33-0.44 Nm) more than the total torque reading with the adjuster plug tightened.
- Tighten the adjuster plug locknut securely.
Preload torque tends to drop off when the locknut is tightened. Even so, the torque reading must be rechecked with the locknut tight, and the torque must still be 3-4 inch lbs. (0.33-0.44 Nm) more than the total.Sector Shaft Overcenter
- Center the gear shaft.
- Loosen the sector shaft adjusting screw locknut, then tighten the sector shaft adjusting screw.
- Tighten the locknut and, using an inch pound torque wrench, rotate the sector shaft 90° to either side of center, noting the torque reading over center. The highest reading is what counts.
- Continue adjusting and checking the preload until the preload is 4-8 inch lbs. (0.44-0.89 Nm) for a new gear, do not exceed 18 inch lbs. (2 Nm). For a gear having more than 400 miles, the preload should be 4-5 inch lbs. (0.44-0.56 Nm) do not exceed 14 inch lbs. (1.5 Nm).
REMOVAL & INSTALLATION
- Place the wheels in a straight-ahead position.
- Remove the Pitman arm.
- Place a drain pan under the gear and disconnect the hoses at the gear.
- Matchmark and disconnect the gearshaft coupling.
- Support the gear and remove the mounting bolts. Remove the steering gear.
- Installation is the reverse of removal. Torque the Pitman arm nut to 175 ft. lbs. (237 Nm); the mounting bolts to 85 ft. lbs. (115 Nm) on models through 1977 or 100 ft. lbs. (135 Nm) on 1978-88 models.