Steering Gear - Power GMC Cab & Chassis R3500

DESCRIPTION

Steering gear is a variable ratio, recirculating ball type. Control valves are located inside steering gear housing.

A 4-character build date is stamped in the cover. If an "X" appears after the build date, the steering housing is equipped with the interim designed pitman shaft seal assembly. (Scheme 4)

TROUBLE SHOOTING

Refer to TROUBLE SHOOTING - BASIC PROCEDURES article in the GENERAL TROUBLE SHOOTING section.

LUBRICATION

See POWER STEERING GENERAL SERVICING article in the STEERING section.

TESTING

See POWER STEERING GENERAL SERVICING article in the STEERING section.

Note. See TROUBLE SHOOTING - BASIC PROCEDURES article in the GENERAL INFORMATION section.

Scheme 4

THRUST BEARING PRELOAD

1. Remove steering gear from vehicle. See «STEERING GEAR»(/gmc/cab-chassis-r3500/1987-1991/remont/manual-power-steering/#steering-gear-power) under REMOVAL & INSTALLATION in this article. Rotate gear lock-to-lock several times to drain fluid. Loosen adjuster plug lock nut. Using spanner wrench, turn adjuster plug clockwise until plug is seated in housing. Torque will be about 20 ft. lbs. (27 N.m).
2. Index mark housing opposite one hole in adjuster plug. (Scheme 5) Measure back about 1/2" counterclockwise from mark. Mark housing. Rotate plug counterclockwise until hole in adjuster aligns with second mark.
3. Tighten lock nut. Ensure adjuster plug remains in position. Attach INCH lb. torque wrench to end of stub shaft. Turn stub shaft to right stop, then back 1/4 turn.
4. Using torque wrench, measure rotational torque required to turn shaft. Reading should be taken with handle of torque wrench near vertical while turning it counterclockwise at an even rate. Reading should be between 4-10 INCH lbs. (.4-1.1 N.m). If not, repeat procedure.

Scheme 5

OVER-CENTER PRELOAD

1. Ensure steering gear is centered. Loosen pitman shaft adjuster screw lock nut. Tighten pitman shaft lash adjuster screw. Retighten lock nut. Measure gear over-center torque by rotating torque wrench attached to stub shaft in a 90 degree arc 45 degrees on each side of center. Record highest reading.
2. Continue adjustment until over-center reading is within specification. See «LASH ADJUSTMENT PRELOAD»(/gmc/cab-chassis-r3500/1987-1991/remont/manual-power-steering/#steering-gear-power). Ensure lock nut is tight when reading is obtained. (Scheme 6)

LASH ADJUSTMENT PRELOAD

Scheme 6

Removal

1. Center steering gear. If necessary for clearance, remove steering column. Raise and support vehicle. Place drain pan under steering gear assembly. Center steering gear. Disconnect hydraulic hoses from gear. Cap ends. Disconnect steering linkage from pitman arm.
2. Remove pitman arm from gear. Remove flexible coupling clamp bolt. Remove steering gear-to-frame bolts. Remove gear from flexible coupling and frame.

Installation

To install, reverse removal procedure. Fill pump reservoir. Bleed air from system. See the POWER STEERING GENERAL SERVICING article in the STEERING section.

Disassembly

1. Cap all openings in gear. Clean gear exterior completely. Mount gear in vise so that pitman shaft points downward. Rotate housing end plug retainer ring until one end of plug is over hole in housing.
2. Force end of ring from groove in housing. Remove ring. Rotate stub shaft counterclockwise to force housing end plug from housing. Rotate stub shaft clockwise 1/2 turn to draw rack piston inward. CAUTION: DO NOT rotate stub shaft more than it is necessary to remove plug, as ball bearings will fall out of worm and rack piston assembly.
3. Remove rack piston end plug. Remove lock nut from pitman shaft adjuster. Remove pitman shaft cover. Remove and discard "O" ring or gasket from cover. Turn stub shaft until pitman shaft teeth are centered in housing.
4. Using a soft-faced hammer, tap end of pitman shaft to free shaft from housing. Remove pitman shaft. Remove adjuster plug lock nut. Using a spanner wrench, remove adjuster plug.
5. Insert Rack Piston Arbor (J-21552) into end of rack piston assembly until arbor just contacts worm shaft. Threaded arbor will keep recirculating balls from falling out of rack piston. Turn stub shaft counterclockwise to force rack piston onto arbor. Remove rack piston and arbor as an assembly.
6. Take care to keep arbor fully inserted so recirculating balls will not fall out. Remove stub shaft and control valve assembly from housing. Remove worm, wormshaft lower thrust bearing, and races from housing.

Inspection

1. Clean all internal parts in solvent and dry with compressed air. Avoid wiping valve parts with cloth. Lint may cause binding of mechanism.
2. DO NOT steam clean hydraulic parts. If further disassembly is required, see appropriate OVERHAUL sub-heading in this article.

Reassembly

1. Lubricate all parts with power steering fluid before reassembly. Install lower thrust bearing and races on worm shaft. (Scheme 4) NOTE: If conical thrust races are used, ensure tapered surfaces are parallel to each other and that cupped sides face toward stub shaft.
2. Place worm shaft in valve body. Install "O" ring in valve body. Align notch in valve body with pin in worm shaft. Install valve body and worm assembly into housing. Installation is correct when fluid return port in housing is fully visible.
3. Place seal protector over stub shaft. Using new "O" ring, install adjuster plug until it seats against valve body.
4. Remove seal protector from housing. Loosely install adjuster plug lock nut. Insert rack piston (with arbor to retain recirculating balls) into housing. Align worm and rack piston. Turn stub shaft clockwise to engage worm. Maintain pressure on arbor until worm is fully engaged.
5. Rotate stub shaft clockwise to align middle rack groove in rack piston with center of pitman shaft roller bearing. Remove arbor. Install a new pitman shaft cover seal.
6. Thread pitman shaft cover onto adjuster screw until bottoms. Back off 1/2 turn. Install pitman shaft so that center gear tooth meshes with center groove in rack piston. Install cover attaching bolts.
7. Install adjuster lock nut halfway onto pitman shaft. Install piston and plug in rack piston. Install housing end plug "O" ring, end plug and retainer ring. Adjust worm bearing preload and over-center preload. Refer to the appropriate ADJUSTMENT procedure in this article.

1. Using a screwdriver, carefully remove thrust bearing retainer. Discard retainer. Remove thrust bearing spacer, thrust bearing and bearing races. Remove and discard adjuster plug "O" ring.
2. Remove snap ring. Remove and discard dust seal. Pry oil seal from adjuster plug and discard seal. Inspect bearing. By pressing out from spacer end, remove bearing (if necessary). (Scheme 4)

Inspect thrust bearing for cracks. Check rollers for pitting, scoring, or cracking. Check thrust races and spacer for damage. Replace parts as necessary.

1. Press bearing into adjuster plug (identification end facing arbor) until bearing bottoms in bore. Install oil seal with spring in seal facing adjuster plug. Install dust seal into adjuster plug.
2. Rubber face of dust seal must face away from plug. Install snap ring. Install adjuster plug "O" ring. Assemble thrust bearing, thrust bearing race, and thrust bearing spacer on adjuster plug. Flanges of both thrust washers face away from plug. Install spacer. Using a punch, tap new retainer into position.

If installed, remove Rack Piston Arbor (J-21552) from rack piston. If arbor was not used, remove worm shaft, lower thrust bearing and bearing races from rack piston. Remove piston ring and back-up "O" ring from rack piston. Remove ball guide clamp and ball guide. Remove all recirculating balls from rack piston.

1. Clean and dry all parts. Inspect worm shaft and rack piston grooves for scoring. Inspect ball bearings for damage. If any ball bearings are damaged, replace entire set. Check ball guides for pinching of ends.
2. Inspect lower thrust bearing races for cracking, scoring, or pitting. If either part is damaged, replace wormshaft and rack piston as an assembly. Inspect rack piston teeth for chips, cracks, dents or scoring.

1. Lubricate with power steering fluid and carefully install new Teflon seal and "O" ring onto rack piston. Install worm shaft into rack piston until worm shaft touches piston shoulder. While turning worm shaft counterclockwise, insert ball bearings into rack piston. NOTE: See «RACK PISTON & WORM ASSEMBLY BALL BEARINGS»(/gmc/cab-chassis-r3500/1987-1991/remont/manual-power-steering/#steering-gear-power) for number of balls to be installed. ENSURE light and dark colored balls are installed alternately, as Black balls are.0005" (.013 mm) smaller than Silver balls.
2. Install correct number of balls in ball guide, alternating ball colors. Bearings in guide must be in sequence with bearings in rack piston. Hold balls in place with chassis lubricant. Install return ball guide assembly into position.
3. Install clamp. Tighten cap screws. (Scheme 7) Insert Rack Piston Arbor (J-21552) into rack piston until it contacts worm shaft. Maintain pressure on arbor, and back worm out of rack piston. DO NOT allow ball bearings to drop out.

RACK PISTON & WORM ASSEMBLY BALL BEARINGS

Scheme 7

Scheme 8

1. Remove and discard stub shaft cap "O" ring. Lightly tap end of stub shaft against wood block until shaft cap is free of valve body. Pull stub shaft outward until drive pin hole is visible. (Scheme 8) CAUTION: DO NOT pull shaft more than 1/4" (6 mm) or spool valve may become cocked in valve body.
2. Disengage drive pin. Remove stub shaft from valve body and spool assembly with a twisting motion. If binding occurs, realign valve. CAUTION: DO NOT force stub shaft or spool out of valve body.
3. Remove spool valve from valve body with twisting motion. Remove and discard all "O" rings and Teflon rings.

1. Wash all parts in solvent and blow dry. Check for leaks between stub shaft and torsion bar. Check for nicks and scores on stub shaft. Sand down with Crocus cloth if possible. Check notch valve body skirt for wear.
2. Check spool valve fit in valve body. With "O" ring removed, lubricate spool valve with power steering fluid. Rotate spool valve in valve body. If valve does not rotate freely, replace complete valve.
3. Valve assembly is balanced during assembly. If replacing any parts other than rings or seals, replace complete assembly.

1. Lubricate valve body components with power steering fluid. Install new "O" rings in seal grooves. Install new Teflon rings over "O" rings. Take care not to damage seal rings during installation. NOTE: Teflon seal rings may appear to be distorted after installation. However, heat of operation will straighten them.
2. Lubricate replacement spool valve damper "O" ring with petroleum jelly and install on spool valve. Carefully insert spool valve into valve body.
3. Push spool valve through valve body until locating pin hole is visible at opposite end of valve body, and spool valve is flush with notched end of valve. Install stub shaft into spool valve and valve body.
4. Align stub shaft locating pin with spool valve locating hole. Align notch in stub shaft cap with pin in valve body. Press stub shaft and spool valve into valve body. Install stub shaft cap "O" ring into valve body.

1. Remove pitman shaft seal snap ring. Remove seals and washers. (Scheme 4) Press pitman shaft bearing out of housing from lower end.
2. If hose connector seat is being replaced, tap the seat with a 5/16" x 18 thread tap. Thread connector seats ONLY 2-3 threads. Install bolt with flat washer and nut into seat. Hold bolt while tightening nut to extract seat.

1. If housing bore is severely worn, scored or pitted, replace housing. Minor scratches may be removed with crocus cloth.
2. Inspect all retaining ring, bearing and seal surfaces in housing. If any surface is worn or damaged, replace housing.

1. Install pitman shaft bearing in steering housing using Handle (J-8092) and Adapter (J-22407). Position bearing so identification marks face away from tool. Press in bearing until tool bottoms against housing. DO NOT bottom bearing in housing.
2. Install seals with lips facing toward housing bore. Install snap ring.

TORQUE SPECIFICATIONS

TORQUE SPECIFICATIONS

See also:
• TROUBLE SHOOTING - BASIC PROCEDURES
• STEERING GEAR