Suspension - Front (Coil) Chevrolet Forward Control P30

DESCRIPTION

Independent front suspension consists of upper and lower control arms with steering knuckle mounted between ball joints. (Scheme 1) Control arms are mounted on pivot shafts. Coil springs are mounted between lower control arm and a formed seat in suspension crossmember. Some models have urethane air cylinders inside the coil springs. Shock absorbers fit between lower control arm and frame. A stabilizer bar is mounted to frame side rails and connected to lower control arms.

Scheme 1

WHEEL ALIGNMENT SPECIFICATIONS & PROCEDURES

Note. See ALIGNMENT SPECIFICATIONS/PROCEDURES article in the WHEEL ALIGNMENT Section.

FRONT WHEEL BEARINGS

1. Raise and support vehicle. Remove hub dust cap and cotter pin. Tighten spindle nut to 12 ft. lbs. (16 N.m) while turning wheel forward by hand. Back off nut until just loose.
2. Finger tighten nut until snug. Loosen nut slightly (no more than 1/2 flat) until NEW cotter pin can be installed. Install NEW cotter pin and measure hub end play. Hub end play (in and out) should be .001-.005" (.03-.13 mm) when properly adjusted. Install dust cap.

RIDING HEIGHT

Note. See ALIGNMENT SPECIFICATIONS/PROCEDURES article in the WHEEL ALIGNMENT Section.

Upper Ball Joint

1. Upper ball joint is spring-loaded in socket to minimize looseness and compensate for normal wear. Raise and support vehicle with jack stand under lower control arm. Remove wheel and tire assembly.
2. Inspect ball joint for lateral shake by gripping hub/rotor assembly at top and bottom, and moving spindle inward and outward. Replace ball joint if any lateral movement exists.
3. Check ball joint, only with ball joint disconnected from steering knuckle, to see if ball joint can be rotated by finger pressure. Replace if ball joint can be twisted. Inspect upper ball joint rubber grease seal for cracks, cuts or tears. Replace as necessary.

Lower Ball Joint

1. Lower ball joint wear may be checked without disassembling ball joint stud. Raise and support vehicle at wheel and hub with jack stand.
2. Measure distance between top of ball joint stud and tip of lower grease fitting. (Scheme 2) Move support to lower control arm and allow wheel and hub to hang free.
3. Measure distance again. If difference between measurements exceeds.094" (2.38 mm), replace ball joint. Inspect lower ball joint rubber grease seal for cracks, cuts or tears. Replace as necessary.

Scheme 2

REMOVAL & INSTALLATION

Removal

1. Raise and support vehicle. Remove wheel and tire assembly. Remove brake caliper and hang aside with wire. DO NOT allow brake caliper to hang by brake line.
2. Remove dust cap, cotter pin, spindle nut and washer. Carefully remove hub/rotor assembly to avoid damage to spindle threads. Remove outer bearing, inner grease seal and inner bearing.
3. Clean bearings and inspect bearings and races for damage. If races require removal from hub, drive old races from hub using a hammer and a brass drift inserted through notches of hub.

Installation

1. To install, reverse removal procedure. Place hub/rotor assembly onto Hub/Rotor Support (J-9746-02 ). Using Bearing Race Installer (J-8457 ), install outer bearing race into hub/rotor assembly. Using Bearing Race Installer (J-8449 ), install inner bearing race into hub/rotor assembly.
2. Pack bearings with high-temperature bearing grease. Install NEW grease seal until seal is even with hub surface. Lubricate seal lip and hub cavity with wheel bearing grease.
3. To complete installation, reverse removal procedure. Tighten bolts and nuts to specification. See «TORQUE SPECIFICATIONS»(/chevrolet/forward-control-p30/1985-1999/remont/suspension-front/#suspension-front-coil) table at end of article. Adjust wheel bearings. See «FRONT WHEEL BEARINGS»(/chevrolet/forward-control-p30/1985-1999/remont/suspension-front/#suspension-front-coil__front-wheel-bearings) under ADJUSTMENTS. Lower vehicle and check wheel alignment. See ALIGNMENT SPECIFICATIONS/PROCEDURES article in the WHEEL ALIGNMENT Section.

Raise and support vehicle. Remove wheel and tire assembly. Remove shock absorber retaining bolt, nut and washer from lower control arm. Remove shock absorber retaining bolt, nut and washer from frame. Remove shock absorber from vehicle.

Note. Purging air from non-spiral groove shock is not required as reservoir has gas-charged cell. Spiral groove shock has air-charged cell and air must be purged.

Inspection

1. On spiral groove shock, purge air from pressure chamber by mounting shock in vise (top end up) and fully extending unit. Reverse position (top end down) and fully collapse unit. Repeat procedure several times.
2. Bench check shock unit by mounting in vise with top end up (top end down on gas-charged shocks). DO NOT clamp vise on reservoir tube or mounting threads. Check rubber grommets for deterioration and replace as needed.
3. Operate shock by hand at various rates of speed and note resistance. Rebound force is normally stronger than compression force. If resistance is not smooth and constant, replace shock.

To install, reverse removal procedure. Tighten bolts and nuts to specification. See TORQUE SPECIFICATIONS table at end of article.

Raise and support vehicle. Remove wheel and tire assembly. Remove stabilizer bar-to-frame retaining bolts, washers and clamps. Disconnect stabilizer bar from frame. Remove stabilizer bar-to-lower control arm retaining bolts, nuts, washers and clamps. Disconnect stabilizer bar from lower control arms. Remove stabilizer bar and bushings from vehicle. Check all rubber bushings for excessive wear, deterioration or damage. Replace as necessary.

To install, reverse removal procedure. Bushings should be installed with slit area toward front of vehicle. Apply rubber lubricant to bushings to aid in installation. Tighten bolts and nuts to specification. See TORQUE SPECIFICATIONS table at end of article.

1. Raise and support vehicle with jack stand under frame, with control arms hanging free. Remove wheel and tire assembly. Disconnect shock absorber and stabilizer bar at lower control arm. Install Spring Remover (J-23028-01 ) on floor jack. (Scheme 3) Position assembly under lower control arm so shaft seats in grooves of spring remover. WARNING: Securely bolt Spring Remover (J-23028-01 ) to floor jack, and install safety chain through lower control arm and coil spring to prevent personal injury.
2. If air cylinders are installed in coil springs, remove valve cap and valve core. Pry on air cylinder to release air pressure. Reinstall valve core and valve cap to retain vacuum condition. Push air cylinder upward toward top of spring as far as possible. Install safety chain around coil spring and through lower control arm.
3. Raise floor jack to release spring tension on lower control arm shaft. Remove control arm shaft-to-crossmember "U" bolts. Carefully lower floor jack until all tension is released from coil spring. Remove safety chain and coil spring. Remove air cylinder (if equipped).
4. To check air cylinder for leaks, inflate air cylinder to 20 psi (1.4 kg/cm 2 ) and submerge in water. Check for air bubbles. Replace air cylinder if leaks exist.

1. To install, reverse removal procedure. Install air cylinder so protector plate is positioned toward upper control arm, and air valve protrudes through hole in lower control arm. Ensure front indexing hole in lower control arm shaft aligns with crossmember attaching studs.
2. Install and inflate air cylinder to 60 psi (4.3 kg/cm 2 ). Lower vehicle and reduce air cylinder pressure to 40-50 psi (2.8-3.6 kg/cm 2 ). Tighten bolts and nuts to specification. See «TORQUE SPECIFICATIONS»(/chevrolet/forward-control-p30/1985-1999/remont/suspension-front/#suspension-front-coil) table at end of article. Lower vehicle and check wheel alignment. See ALIGNMENT SPECIFICATIONS/PROCEDURES article in the WHEEL ALIGNMENT Section.

Scheme 3

1. Raise and support vehicle with jack stand under frame, with control arms hanging free. NOTE: DO NOT place jack stands under lower control arm. Spring tension is needed to break loose ball joint stud.
2. Remove wheel and tire assembly. Remove brake caliper and hang aside with wire. DO NOT allow brake caliper to hang by brake line. Remove hub/rotor assembly. Remove splash shield. Remove cotter pin and nut from tie rod end. Use Tie Rod Remover (J-6627-A ) to separate tie rod end from steering knuckle.
3. If replacing steering knuckle, carefully remove steering knuckle grease seal. Position floor jack under lower control arm between ball joint and spring seat. Raise floor jack until lower control arm is just supported. CAUTION: Lower control arm must be supported with floor jack during removal and installation of steering knuckle.
4. Remove cotter pins and nuts from upper and lower ball joints. Using Ball Joint Separator (J-23742 ), separate ball joint studs from steering knuckle. (Scheme 4) Raise upper control arm to disengage ball joint stud from steering knuckle. Remove steering knuckle.

Inspect tapered holes in steering knuckle for out-of-round, deformation or damage. Inspect spindle for worn or damaged threads. Replace steering knuckle as necessary.

1. To install, reverse removal procedure. Install NEW grease seal on steering knuckle (if removed). Tighten ball joint stud nuts to align cotter pin holes as necessary. Install tie rod end stud into steering knuckle.
2. Install Steering Linkage Installer (J-29193 ) or (J-29194 ). Tighten steering linkage installer to 40 ft. lbs. (54 N.m) to seat tie rod taper. Remove steering linkage installer and install tie rod end stud nut.
3. To complete installation, reverse removal procedure. Adjust wheel bearings. See «FRONT WHEEL BEARINGS»(/chevrolet/forward-control-p30/1985-1999/remont/suspension-front/#suspension-front-coil__front-wheel-bearings) under ADJUSTMENTS. Tighten bolts and nuts to specification. See «TORQUE SPECIFICATIONS»(/chevrolet/forward-control-p30/1985-1999/remont/suspension-front/#suspension-front-coil) table at end of article. Lower vehicle and check wheel alignment. See ALIGNMENT SPECIFICATIONS/PROCEDURES article in the WHEEL ALIGNMENT Section.

Scheme 4

1. Raise and support vehicle with jack stand under lower control arm between ball joint and spring seat. Jack stand must remain under lower control arm during upper ball joint servicing to maintain lower control arm and coil spring positioning.
2. Remove wheel and tire assembly. Remove brake caliper and hang aside with wire. DO NOT allow brake caliper to hang by brake line. Remove grease fitting and cotter pin from upper ball joint stud. Loosen ball joint stud nut 2 turns. DO NOT remove nut at this time.
3. Install Ball Joint Separator (J-23742 ) between upper and lower ball joint studs. (Scheme 4) Extend bolt on ball joint separator to loosen ball joint stud from steering knuckle. Remove ball joint separator and ball joint stud nut. Separate ball joint from steering knuckle.
4. Using drill and 1/8" (3.18 mm) drill bit, drill 1/4" (6.35 mm) deep hole in ball joint retaining rivets. Using 1/2" (12.7 mm) drill bit, drill out rivet heads. Using a hammer and small punch, drive out rivets and remove upper ball joint from upper control arm.

To install, reverse removal procedure. Use NEW nuts and bolts to install ball joint into upper control arm. Install grease fitting and lubricate NEW ball joint. Tighten bolts and nuts to specification. See TORQUE SPECIFICATIONS table at end of article. Lower vehicle and check wheel alignment. See ALIGNMENT SPECIFICATIONS/PROCEDURES article in the WHEEL ALIGNMENT Section.

1. Raise and support vehicle with jack stand under lower control arm between ball joint and spring seat. Jack stand must remain under lower control arm during lower ball joint servicing to maintain lower control arm and coil spring positioning.
2. Remove wheel and tire assembly. Remove brake caliper and hang aside with wire. DO NOT allow brake caliper to hang by brake line. Remove grease fitting, rubber grease seal and cotter pin from lower ball joint stud. Loosen ball joint stud nut 2 turns. DO NOT remove nut at this time.
3. Install Ball Joint Separator (J-23742 ) between upper and lower ball studs. (Scheme 4) Extend bolt on ball joint separator to loosen ball joint stud from steering knuckle. Remove ball joint separator. Separate ball joint from steering knuckle.
4. Place a wooden block between upper control arm and frame to keep steering knuckle assembly out of the way. Assemble on control arm, "C" Clamp (J-9519-23 ) and Removers (J-9519-7 and J-9519-28 ) from Ball Joint Remover/Installer Set (J-9519-D ). (Scheme 5) Remove ball joint from lower control arm.

1. Assemble on control arm, "C" Clamp (J-9519-23 ) and Installer (J-9519-16 ) from ball joint remover/installer set. (Scheme 5) Reverse removal procedure to install ball joint into lower control arm. Ensure bleed vent in rubber grease seal is facing forward. Install grease fitting and lubricate NEW ball joint.
2. To complete installation, reverse removal procedure. Tighten bolts and nuts to specification. See «TORQUE SPECIFICATIONS»(/chevrolet/forward-control-p30/1985-1999/remont/suspension-front/#suspension-front-coil) table at end of article. Lower vehicle and check wheel alignment. See ALIGNMENT SPECIFICATIONS/PROCEDURES article in the WHEEL ALIGNMENT Section.

Scheme 5

1. Raise and support vehicle with jack stand under lower control arm between ball joint and spring seat. Jack stand must remain under lower control arm during upper control arm servicing to maintain lower control arm and coil spring positioning.
2. Remove wheel and tire assembly. Remove brake line bracket from upper control arm. Remove grease fitting and cotter pin from upper ball joint stud. Loosen ball joint stud nut. Using Ball Joint Separator (J-23742 ), position large cupped end of separator over upper ball stud nut, and position pilot-threaded end of tool onto lower ball stud. (Scheme 4)
3. Extend bolt on ball joint separator to loosen ball joint stud from steering knuckle. Remove ball joint separator and stud nut. Separate upper ball joint from steering knuckle.
4. Remove upper control arm pivot shaft-to-frame nuts. Remove upper control arm alignment shims and spacers. Tape alignment shims together and tag location for reassembly. Remove frame bracket bolts and washers. Remove upper control arm from frame bracket.

To install, reverse removal procedure. Ensure alignment shims are installed in original position, with concave and convex sides together. Tighten bolts and nuts to specification. See TORQUE SPECIFICATIONS table at end of article. Lower vehicle and check wheel alignment. See ALIGNMENT SPECIFICATIONS/PROCEDURES article in the WHEEL ALIGNMENT Section.

Note. Normal shim pack will leave at least 2 bolt threads exposed beyond nut. If 2 bolt threads are not exposed, check for damaged control arms and components. Thickness difference between front and rear shim packs must not exceed .30" (7.6 mm). Front shim pack thickness must be at least .24" (6.1 mm). Tighten thinner shim pack nut first.

Bushing Replacement (G15/1500 & G25/2500)

1. Remove upper control arm from vehicle. See «UPPER CONTROL ARM»(/chevrolet/forward-control-p30/1985-1999/remont/suspension-front/#suspension-front-coil) under REMOVAL & INSTALLATION. Place upper control arm in soft-jawed vise. Remove nuts from ends of pivot shaft. Using components from Control Arm Bushing Service Set (J-24435-A ), remove bushing from control arm. (Scheme 6)
2. Remove pivot shaft from control arm. Note direction of shaft installation. Repeat procedure to remove remaining bushing. Reverse removal order to install bushings. (Scheme 7) Ensure bushings are fully seated.

Scheme 6

Scheme 7

Bushing Replacement (G35/3500 & P35/3500)

1. Components can be changed with control arm in vehicle. To remove components, disconnect upper control arm from frame. See «UPPER CONTROL ARM»(/chevrolet/forward-control-p30/1985-1999/remont/suspension-front/#suspension-front-coil) under REMOVAL & INSTALLATION. Unscrew bushings and slide pivot shaft out of upper control arm. Remove grease fitting. Remove inner seals from between bushings and pivot shaft.
2. To install, slide NEW seal onto each end of upper control arm pivot shaft. Install pivot shaft into upper control arm. Install NEW bushings. Adjust pivot shaft until centered in control arm, then tighten bushing nuts to specification. (Scheme 8) See «TORQUE SPECIFICATIONS»(/chevrolet/forward-control-p30/1985-1999/remont/suspension-front/#suspension-front-coil) table at end of article. Check shaft for free rotation. Install grease fittings and lubricate bushings.

Scheme 8

LOWER CONTROL ARM

1. Raise and support vehicle with jack stand under lower control arm between ball joint and spring seat. Jack stand must remain under lower control arm during upper control arm servicing to maintain lower control arm and coil spring positioning.
2. Remove wheel and tire assembly. Remove brake caliper. Remove coil spring. See «COIL SPRINGS»(/chevrolet/forward-control-p30/1985-1999/remont/suspension-front/#suspension-front-coil) under REMOVAL & INSTALLATION. Support inboard end of control arm. Remove cotter pin from lower ball joint stud. Loosen ball joint stud nut one turn.
3. Using Ball Joint Separator (J-23742 ), position large cupped end of separator over upper ball stud nut, and position pilot-threaded end of tool onto lower ball stud. (Scheme 4)
4. Extend bolt of ball joint separator to separate ball stud from steering knuckle. Remove ball joint separator and stud nut. Separate lower ball joint from steering knuckle. Remove lower control arm.

To install, reverse removal procedure. Ensure front indexing hole in lower control arm shaft aligns with crossmember attaching studs. Tighten bolts and nuts to specification. See TORQUE SPECIFICATIONS table at end of article. Lower vehicle and check wheel alignment. See ALIGNMENT SPECIFICATIONS/PROCEDURES article in the WHEEL ALIGNMENT Section.

1. Remove lower control arm. See «LOWER CONTROL ARM»(/chevrolet/forward-control-p30/1985-1999/remont/suspension-front/#suspension-front-coil__lower-control-arm) under REMOVAL & INSTALLATION. Remove nuts and washers from control arm shaft.
2. Install control arm in press for rear bushing removal. Press on front of lower control arm shaft and remove rear bushing. Remove lower control arm shaft.
3. Using Bushing Remover (J-24435-3 ), Spacer (J-24435-2 and J-24435-6 ) and "C" Clamp (J-24435-7 ), remove front bushing.
4. Use Installer (J-24435-4 ), Spacer (J-24435-6 ) and "C" Clamp (J-24435-7 ) to install NEW front bushing. (Scheme 9) Stake front bushing in at least 2 areas.
5. Align outer tube hole so it faces front or toward staked bushing. Install lower control arm shaft and repeat procedure to install remaining bushing. Install washers and nuts on lower control arm shaft. Install lower control arm.

Scheme 9

1. Raise and support vehicle under frame, with control arms hanging free. Remove wheel and tire assembly. Disconnect shock absorber and stabilizer bar at lower control arm.
2. Place jack under lower control arm. Jack must be positioned inward of coil spring and in depression areas of control arm. Install safety chain over upper control arm on inside of stabilizer bar and outside of shock absorber.
3. Remove lower control arm "U" bolt nuts and washers. Slowly lower the control arm from frame releasing coil spring tension. Remove grease fittings. Remove bushing nuts and remove lower control arm shaft from control arm. Remove seals located between bushing and lower control arm shaft.
4. To install, slide NEW seals onto lower control arm shaft. Install shaft into lower control arm. Adjust shaft until centered in control arm, then tighten bushing nuts to specification. (Scheme 10) See «TORQUE SPECIFICATIONS»(/chevrolet/forward-control-p30/1985-1999/remont/suspension-front/#suspension-front-coil) table at end of article. Check shaft for free rotation. Install grease fittings and lubricate bushings.
5. Install lower control arm. Ensure front indexing hole in lower control arm shaft aligns with crossmember attaching stud. To complete installation, reverse removal procedure. Tighten bolts and nuts to specification. See «TORQUE SPECIFICATIONS»(/chevrolet/forward-control-p30/1985-1999/remont/suspension-front/#suspension-front-coil) table at end of article. Lower vehicle and check wheel alignment. See ALIGNMENT SPECIFICATIONS/PROCEDURES article in the WHEEL ALIGNMENT Section.

Scheme 10

CROSSMEMBER & SUSPENSION UNIT

Note. Front suspension components may be serviced separately as previously outlined or, if extensive repairs are necessary, crossmember and suspension unit can be removed as an assembly.

1. Disconnect battery negative cable. Raise and support vehicle. Remove wheel and tire assembly. Remove brake line bracket from upper control arm.
2. Support vehicle with jack stands at frame side rails, and lower hoist. Clean area around brake line fitting. Remove brake line from brake caliper and plug openings.
3. Disconnect tie rod end from steering knuckle. Remove stabilizer bar and shock absorber from lower control arm. Remove brake line bracket bolt from front suspension crossmember. CAUTION: Brake line clips must be disconnected from front suspension unit, or severe damage to brake line will result when unit is lowered from vehicle.
4. Remove engine mount support bracket-to-front suspension crossmember bolts. Remove crossmember-to-lower frame rail bolts. Raise hoist and support suspension crossmember. Support engine. NOTE: Support engine BEFORE lowering front suspension unit.
5. Remove upper control arm bracket-to-frame side rail bolts. Suspension unit is now disconnected. Lower hoist and remove front suspension unit from vehicle.

To install, reverse removal procedure. Lubricate suspension components. Bleed brake system. Tighten bolts and nuts to specification. See TORQUE SPECIFICATIONS table at end of article. Lower vehicle and check wheel alignment. See ALIGNMENT SPECIFICATIONS/PROCEDURES article in the WHEEL ALIGNMENT Section.

TORQUE SPECIFICATION

TORQUE SPECIFICATIONS

See also:
• TORQUE SPECIFICATIONS
• FRONT WHEEL BEARINGS
• LOWER CONTROL ARM