Steering Gear - Power GMC Vandura I

DESCRIPTION

Steering gear is a recirculating ball-type, available in either a constant or a variable ratio design. Steel balls form a "rolling thread" between steering gear worm shaft and rack/piston nut. Worm shaft thrust is absorbed by a thrust bearing and two races at lower end, and by a bearing in adjuster plug at upper end.

This design puts spring pressure on worm shaft to ensure proper thrust bearing preload. Adjuster plug provides initial preload adjustment and service adjustment (when repairing gear). As worm shaft is turned right, rack/piston is moved upward in gear.

As worm shaft is turned left, rack/piston is moved downward in gear. The rack/piston teeth mesh with sector, which is forged as part of sector shaft. Rotating worm shaft moves sector shaft, which turns wheels through mechanical linkage. (Scheme 1)

TROUBLE SHOOTING

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

LUBRICATION & TESTING

See appropriate POWER STEERING GENERAL SERVICING article in this section. Refer to the following list.

1. «POWER STEERING GENERAL SERVICING»(/gmc/vandura/i-1970-1996/remont/manual-power-steering/#power-steering-general-servicing) (for all 1983 models)
2. «POWER STEERING GENERAL SERVICING»(ref-54150) (for 1984-86 models)

Exploded View of Saginaw Rotary Valve Power Steering Gear. Scheme 1

THRUST BEARING PRELOAD ADJUSTMENT

1. Remove steering gear from vehicle. Remove adjuster plug lock nut. Turn adjuster plug clockwise with a spanner wrench until plug is seated in housing. This will require 20-30 ft. lbs. (27-41 N.m) of torque.
2. Place an index mark on housing opposite one spanner wrench hole in adjuster plug. Measure 1/2" (13 mm) counterclockwise from mark and again mark housing. Rotate plug counterclockwise until hole in adjuster lines up with second mark.
3. Tighten lock nut. Ensure adjuster remains in position.

Note. If reading does not fall within this range, adjuster plug may have turned while lock nut was being tightened. Steering gear may be incorrectly assembled or worm shaft thrust bearings and races may be defective. Repair as required and readjust preload.

Measuring Thrust Bearing Preload Preload should be 4-10 INCH lbs. (.4-1.1 N.m). Scheme 2

OVER-CENTER PRELOAD TORQUE ADJUSTMENT

1. Loosen adjuster screw lock nut. Back off adjuster screw until stopped, then turn in 1 full turn. Rotate input shaft from stop to stop counting number of turns. Turn shaft half way back to center position.
2. Attach an INCH lb. torque wrench to input shaft. Turn shaft from side to side through specified arc on each side of center. See «OVER-CENTER PRELOAD»(/gmc/vandura/i-1970-1996/remont/manual-power-steering/#steering-gear-power) chart. Note torque reading going over center. (Scheme 3)

OVER-CENTER PRELOAD INCH LBS.

Adjusting Over-Center Preload Adjust thrust bearing preload before over-center preload. Scheme 3

Removal

1. Remove collapsible steering column. Raise and support vehicle. Place drain pan under steering gear assembly. Center steering gear. Disconnect hydraulic hoses from gear and cap ends. Disconnect steering linkage from pitman arm. Remove pitman arm from gear.
2. Remove flexible coupling clamp bolt and bolts retaining steering gear to frame. Disconnect gear from flexible coupling and remove gear from vehicle.

Installation

To install, reverse removal procedure. Fill pump reservoir and bleed air from system. See the appropriate POWER STEERING SERVICING article in this section. Refer to the following list.

1. «POWER STEERING GENERAL SERVICING»(/gmc/vandura/i-1970-1996/remont/manual-power-steering/#power-steering-general-servicing) (for all 1983 models)
2. «POWER STEERING GENERAL SERVICING»(ref-54150) (for 1984-86 models)

Disassembly

1. Cap all openings in gear and clean gear exterior throughly. 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 and remove. Rotate input shaft counterclockwise to force housing end plug out of housing. Rotate input shaft clockwise 1/2 turn to draw rack/piston inward. Remove piston end plug. CAUTION: DO NOT rotate shaft more than is necessary to remove plug as ball bearings will fall out of worm and rack piston assembly.
3. Remove lock nut from sector shaft adjuster. Remove sector shaft cover. Remove and discard "O" ring from cover. Turn input shaft until sector shaft teeth are centered in housing.
4. Tap end of sector shaft with a soft-faced hammer to free shaft from housing, then remove sector shaft. Remove adjuster plug lock nut. Remove adjuster plug with a spanner wrench.
5. Insert a rack/piston arbor into the end of the rack/piston until arbor just contacts worm shaft. Turn stub shaft counterclockwise to force rack/piston onto arbor. Remove the rack/piston and arbor as an assembly.
6. Take care to keep arbor fully inserted so ball bearings will not fall out. Remove input shaft and control valve assembly from housing. Remove worm, wormshaft lower thrust bearing, and races from housing.

Scheme 4

1. Lubricate all parts with clean power steering fluid before reassembly. Install the lower thrust bearing and races onto the worm. (Scheme 4) (Scheme 4): Reassembly of Valve Body & Worm Shaft Assembly Cupped side of thrust washers must face toward stub shaft. NOTE: If conical thrust races are used, ensure tapered surfaces are parallel to each other and that cupped sides face toward stub shaft.
2. Install stub shaft cap "O" ring in valve body. Align valve body drive pin on worm with narrow pin slot in valve body. Worm drive lugs must engage in stub shaft cap.
3. Install valve body and worm assembly into housing. Perform installation by pressing directly on valve body only. This will prevent stub shaft "O" ring from disengaging from valve body.
4. Valve body is correctly seated when fluid return port in housing is fully visible. Ensure worm locating pin is fully engaged in valve body. Place seal protector over input shaft, install a new adjuster plug "O" ring, then install adjuster plug.
5. Remove seal protector from housing and loosely install adjuster plug lock nut. Insert arbor and rack/piston into housing. Align worm and rack/piston and turn stub shaft clockwise to engage worm. Maintain pressure on arbor until worm is fully engaged.
6. Turn input shaft clockwise until middle rack groove in rack/piston is aligned with center of sector shaft roller bearing. Remove arbor. Install a new sector shaft cover gasket.
7. Thread sector shaft cover onto adjuster screw until bottomed. Back off 1 1/2 turns. Install sector shaft so that center gear tooth meshes with center groove in rack/piston. Install cover attaching bolts.
8. Install adjuster lock nut halfway onto sector 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 at this time.

1. Remove thrust bearing retainer ring with a screwdriver, taking care not to score needle bearing bore. Discard retainer ring. Remove thrust bearing spacer, thrust bearing and bearing races.
2. Remove and discard adjuster plug "O" ring, then remove input shaft seal retainer. Remove and discard dust seal. Pry input shaft seal from adjuster plug.
3. Inspect needle bearing in adjuster plug. If necessary, remove bearing by pressing out from spacer end. (Scheme 5)

Inspection

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

Exploded View of Adjuster Plug Assembly. Scheme 5

Reassembly

1. Press roller bearing into adjuster plug (identification end facing arbor) until bearing bottoms on input shaft seal bore. Install input shaft seal with spring in seal facing adjuster plug.
2. Install dust seal into adjuster plug. The rubber face of the seal must face away from plug. Install retainer ring and adjuster plug "O" ring.
3. Assemble thrust bearing, thrust bearing race, and thrust bearing spacer on adjuster plug. Using a brass or wooden dowel, press bearing retainer into needle bearing bore.

Remove worm, lower thrust bearing and bearing races from rack piston. Remove piston ring and back-up "O" ring from rack/piston. Remove ball return guide clamp, ball return guide and all ball bearings from rack/piston.

1. Clean and dry all parts. Inspect worm 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. Replace wormshaft and rack/piston as an assembly if either part is damaged. Inspect the rack/piston teeth for chips, cracks, dents or scoring.

1. Install "O" ring and piston ring onto rack/piston using care not to twist them. Install worm into rack/piston until worm is against piston shoulder. Install ball bearings into rack/piston while slowly rotating worm counterclockwise. NOTE: See «RACK PISTON & WORM ASSEMBLY BALL BEARINGS»(/gmc/vandura/i-1970-1996/remont/manual-power-steering/#steering-gear-power) for number of balls to be installed. BE SURE to install light and dark colored balls alternately, as Black balls are.0005" smaller than Silver balls.
2. Install correct number of balls in ball guide. Bearings in guide must be in sequence with bearings in rack/piston. Hold balls in place with chassis lube. Place return ball guide assembly in position.
3. Install clamp and tighten attaching bolts. (Scheme 6) Insert rack/piston arbor into rack/piston until it contacts worm. Maintain pressure on arbor, and back worm out of rack/piston. DO NOT allow ball bearings to drop out of circuits.

RACK PISTON & WORM ASSEMBLY BALL BEARINGS

Installing Ball Bearing into Rack/Piston Assembly Alternate light and dark colored balls when installing. Scheme 6

ROTARY VALVE OVERHAUL

Note. Complete valve assembly is balanced during assembly. If replacement of any part other than rings or seals is necessary, replace complete assembly.

Scheme 7

1. Remove and discard stub shaft cap "O" ring. Invert valve and 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 7) NOTE: DO NOT pull shaft any further than 1/4" (6 mm) or spool valve may become cocked in valve body. (Scheme 7): Pulling Shaft from Valve Assembly Depress pin to remove stub shaft from valve body.
2. Disengage drive pin and carefuly remove stub shaft from valve body and spool assembly with a twisting motion. If binding occurs, realign valve and try removal again. 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.

Exploded View of Valve Body Assembly. Scheme 8

1. Lubricate all valve body components with power steering fluid. Install replacement back-up "O" rings in seal grooves and install replacement seal rings over back-up 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. 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 the stub shaft into the spool valve and valve body.
4. Be sure stub shaft locating pin is aligned with spool valve locating hole. Align notch in stub shaft cap with stub shaft locating pin and press sub shaft and spool valve into valve body. Install stub shaft cap "O" ring into valve body. (Scheme 9)

Aligning Pin and Notch for Input (Stub) Shaft Stub shaft locating pin must align with spool valve locating hole. Scheme 9

1. Remove sector shaft seal retaining ring and remove lower steel washer. Remove lower seal, spacer washer and upper seal from housing. Press sector shaft bearing out of housing from lower end.
2. To remove hose connector seat, tap out seat using a 5/16"-18 thread tap. Thread connector seats ONLY 2-3 threads. Install a bolt with a flat washer and nut into seat.
3. While holding bolt from turning, tighten nut to extract seat from housing. Remove and discard check valve and spring from inlet port.

Gear Housing Seals and Bearing. Scheme 10

1. Replace housing if bore is severly worn, scored or pitted. Minor scratches may be removed with crocus cloth. Inspect housing ball plug for fluid leakage. Seat ball plug with blunt punch.
2. Spray ball area with Loctite Solvent 7559 and dry with compressed air. Cover ball area with Loctite Sealant 290. Allow sealant to cure for 2 hours before assembling gear.
3. Inspect all retaining ring, bearing and seal surfaces in housing. Replace housing if any surface is worn or damaged.

1. Working from upper end, press a new bearing into housing until it is seated .030" (.76 mm) below shoulder in housing bore. Lubricate new seal with power steering fluid.
2. Install single lipped seal and spacer washer only far enough to provide clearance for next seal, washer and retaining ring. DO NOT bottom seal against housing counterbore.
3. Install double lipped seal and steel washer. Install retaining ring. DO NOT allow seals to contact one another. To ensure proper seal action, be sure there is clearance between them.
4. If port seat was removed, position new spring, check valve, and a new seat over opening in housing. Drive into place using a brass drift.

"C", "G", "K", "P", "R" & "V" SERIES

TORQUE SPECIFICATIONS ("C", "G", "K", "P", "R" & "V" SERIES)

"L", "M", "S" & "T" SERIES

TORQUE SPECIFICATIONS ("L", "M", "S" & "T" SERIES)

See also:
• TROUBLE SHOOTING - BASIC PROCEDURES
• POWER STEERING GENERAL SERVICING
• OVER-CENTER PRELOAD