Suspension - Front (2wd) GMC Magnavan G3500

DESCRIPTION

Independent front suspension consists of upper and lower control arms with steering knuckle mounted between ball joints. Control arms mount on inner 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. Hydraulic or gas-charged shock absorbers fit between lower control arm and frame. A stabilizer bar is mounted to frame side rails and is connected to lower control arms by links.

WHEEL ALIGNMENT SPECIFICATIONS & PROCEDURES

See WHEEL ALIGNMENT SPECIFICATIONS & PROCEDURES in WHEEL ALIGNMENT section.

WHEEL BEARING ADJUSTMENT

1. Raise and support vehicle. Remove hub dust cap and cotter pin. Tighten spindle bearing nut to 12 ft. lbs. (16 N.m) while turning wheel forward by hand. Back off nut until it is just loose.
2. Finger tighten nut until snug, then loosen slightly (no more than 1/2 flat) until new cotter pin can be installed. Hub play (in and out) should be .0012-.0050" (.030-.127 mm) when properly adjusted. Install dust cap and wheel cover.

Scheme 1

Upper Ball Joint

1. Upper ball joint stud is spring-loaded in the socket to minimize looseness and compensate for normal wear. Raise vehicle and support at lower control arm. Remove front wheel assembly.
2. Inspect ball joint stud for lateral shake by gripping hub assembly at top and bottom and moving spindle inward and outward. Replace ball joint if any lateral movement exists.
3. Ball joint should be checked to see if stud can be rotated by finger pressure only with ball joint disconnected from steering knuckle. Replace ball joint if stud can be twisted. Inspect upper ball joint rubber grease seal for cuts or tears. Replace ball joint if damage is found.

Lower Ball Joint

1. Lower ball joint wear may be checked without ball stud disassembly. To check lower ball joint, 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. Remeasure distance. If difference exceeds.094" (2.38 mm), replace ball joint. Inspect lower ball joint rubber grease seal for cuts or tears. Replace ball joint if damage is found.

Scheme 2

Removal

1. Raise and support vehicle. Remove wheel and tire assembly. Remove brake caliper and hang aside. DO NOT allow brake caliper to hang by brake hose.
2. Remove dust cap, cotter pin, spindle nut, washer and then remove hub and rotor assembly. Remove outer bearing, inner grease seal and inner bearing.
3. Clean bearings and inspect bearing 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 the hub.

Installation

1. To install, reverse removal procedure. Install outer race using Race Installer (J-8457 ) and Race Installer (J-8449 ) for inner bearing race. Pack bearings with proper lubricant.
2. Install grease seal until seal is even with hub surface. Lubricate seal lip and hub cavity with wheel bearing grease. To complete installation, reverse removal procedure. Adjust wheel bearings. See «WHEEL BEARING ADJUSTMENT»(/gmc/magnavan-g3500/1985-1993/remont/suspension-front/#suspension-front-2wd__wheel-bearing-adjustment) under ADJUSTMENTS & CHECKING in this article.

Removal & Installation

Raise and support vehicle. Remove shock absorber retaining bolts. Remove shock absorber. To install, reverse removal procedure. Tighten all bolts and nuts to specification.

Raise and support vehicle. Remove wheel and tire assembly. Remove stabilizer bar-to-frame retaining bolts and clamps. Disconnect stabilizer bar from lower control arms. Remove stabilizer bar and bushings. Check all rubber bushings for excessive wear or damage.

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.

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. Install Lower Control Arm Shaft Support (J-23028-01 ) on a jack. Position assembly under lower control arm so that shaft seats in grooves of lower control arm shaft support. (Scheme 3)
2. If air bags 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 as far as possible. Install safety chain around coil spring and through lower control arm. WARNING: Safety chain must be installed through lower control arm and coil spring to prevent personal injury.
3. Raise jack to release tension from lower control arm shaft. Remove control arm shaft-to-crossmember "U" bolts. Carefully lower jack until all tension is released from spring. Remove safety chain and coil spring. Remove air cylinder.
4. Air cylinder should be checked for leaks. Inflate air cylinder to 20 psi (1.4 kg/cm 2 ). Submerge in water and check for air bubbles. Replace air cylinder if leaks exist.

Scheme 3

To install, reverse removal procedure. Air cylinder must be installed so protector plate is positioned toward upper control arm. Ensure front indexing hole in lower control arm shaft aligns with crossmember attaching stud.

1. Raise and support vehicle near ball joint so front coil spring remains compressed. Remove wheel and tire assembly. Remove brake caliper, hub and brake rotor assembly. Remove rotor splash shield.
2. Remove cotter pin and tie rod end nut. Using Tie Rod Remover (J-6627-A), remove tie rod stud from steering knuckle arm.
3. Support lower control arm with floor jack. Remove upper and lower ball joint cotter pins and loosen ball joint stud nuts. Using Ball Joint Separator (J-23742 ), separate steering knuckle from ball joint studs. (Scheme 4) Remove ball joint stud nuts and remove steering knuckle.

Inspection

Inspect tapered holes in steering knuckle for out-of-round, deformation or damage. Replace steering knuckle if damaged.

To install, reverse removal procedure. Tighten nuts to specification. If necessary, tighten ball joint and/or tie rod end stud nut to align cotter pin holes. Adjust wheel bearings. See WHEEL BEARING ADJUSTMENT under ADJUSTMENTS & CHECKING in this article.

1. Raise and support vehicle. Support lower control arm with floor jack. Remove wheel and tire assembly. Remove cotter pin from upper ball joint stud. Loosen nut 2 turns. DO NOT remove at this time.
2. Remove brake caliper. Install Ball Joint Separator (J-23742 ) between ball joint studs. (Scheme 4)
3. Extend bolt on ball joint separator to loosen ball joint stud from steering knuckle. Remove ball joint separator and ball joint stud nut. Drill out rivets and remove ball joint assembly.

To install, reverse removal procedure. Use new nuts and bolts to install ball joint. Install grease fitting and lubricate new ball joint.

Scheme 4

1. Raise and support vehicle. Support lower control arm with floor jack. Remove wheel and tire assembly. Remove lower ball joint stud cotter pin. Loosen ball joint stud nut 2 turns. DO NOT remove at this time.
2. Remove brake caliper. Install Ball Joint Separator (J-23742 ) between ball joint studs. Extend bolt on ball joint separator to loosen ball stud. (Scheme 4)
3. Remove ball joint separator and ball joint stud nut. Lift steering knuckle assembly from lower ball joint stud. Support upper control arm with block of wood.
4. Install Ball Joint Remover/Installer Set (J-9519-D ) on control arm and remove ball joint.

To install, reverse removal procedure. Use ball joint remover/installer set to install ball joint. Ensure bleed vent in rubber boot is positioned facing forward. Install grease fitting and lubricate new ball joint with chassis lubricant.

Removal (G10/1500-G20/2500)

1. Raise and support vehicle. Support lower control arm with floor jack. Remove wheel and tire assembly.
2. Remove brake caliper and suspend out of way. Remove cotter pin from upper ball joint stud and loosen nut.
3. Using Ball Joint Separator (J-23742 ), loosen ball joint stud from steering knuckle. Remove ball joint separator and ball joint stud nut. Raise control arm from steering knuckle. Support steering knuckle assembly.
4. Remove upper control arm shaft-to-frame nuts. Remove upper control arm and alignment shims. Tape alignment shims together and tag location for reassembly.

To install, reverse removal procedure. Ensure alignment shims are installed in original location with concave and convex sides together. To complete installation, reverse removal procedure. Check wheel alignment.

Note. Normal shim pack will leave at least 2 bolt threads exposed beyond the nut. If 2 threads cannot be obtained, 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.

Removal (P20/2500 - 30/35000 & G30/3500)

1. Raise and support vehicle. Support lower control arm with floor jack. Remove wheel and tire assembly.
2. Remove brake caliper and suspend out of way. Remove cotter pin from upper ball joint stud and loosen nut. Using Ball Joint Separator (J-23742 ), loosen ball joint stud from steering knuckle. Remove ball joint separator and ball joint nut. Raise control arm from steering knuckle. Support steering knuckle assembly.
3. Loosen upper control arm shaft bushing nuts. (Scheme 5) Loosen control arm shaft-to-frame nuts and remove alignment shims. Tape shims together and tag location for reassembly.
4. Remove control arm shaft-to-frame nuts. DO NOT allow control arm to swing too far away from frame. Use a safety chain to retain control arm in close relationship to frame. Remove bushing nuts and remove upper control arm shaft from control arm. (Scheme 5)

1. To install, reverse removal procedure. Upper control arm shaft must be centered prior to installation. See «UPPER CONTROL ARM BUSHINGS»(/gmc/magnavan-g3500/1985-1993/remont/suspension-front/#suspension-front-2wd) under REMOVAL & INSTALLATION in this article.
2. Ensure alignment shims are installed in original location with concave and convex sides together. To complete installation, reverse removal procedure. Check front end alignment.

Note. Normal shim pack will leave at least 2 bolt threads exposed beyond the nut. If 2 threads cannot be obtained, 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 (G10/1500-20/2500)

1. Mount control arm assembly in a vise. Remove nuts from the ends of control arm shaft. Using components from Control Arm Bushing Service Set (J-24435-A ), remove bushing from control arm.
2. Remove shaft from control arm. Note direction of shaft installation. Repeat procedure to remove remaining bushing. To install, reverse removal procedure. Ensure bushings are fully seated.

Bushing Replacement (P20/2500 - 30/3500 & G30/3500)

1. Components can be changed with control arm in the vehicle. To remove components, upper control arm must be removed from the frame. See «UPPER CONTROL ARM»(/gmc/magnavan-g3500/1985-1993/remont/suspension-front/#suspension-front-2wd) under REMOVAL & INSTALLATION in this article.
2. To install, slide new seal onto each end of upper control arm shaft. Install shaft into upper control arm. Adjust shaft until centered in control arm, then tighten bushing nuts to specification. (Scheme 5) Check shaft for free rotation. Install grease fittings and lubricate bushings.

Scheme 5

1. Remove coil spring. See «COIL SPRING»(/gmc/magnavan-g3500/1985-1993/remont/suspension-front/#suspension-front-2wd) under REMOVAL & INSTALLATION in this article. Support inboard end of control arm. Remove cotter pin from lower ball joint stud, then loosen ball joint stud nut one turn.
2. Using Ball Joint Separator (J-23742 ), position large cupped end of tool over upper ball stud nut and pilot threaded end of tool onto lower ball stud. (Scheme 4) Extend bolt of ball joint separator to separate ball stud from steering knuckle. Remove ball joint separator and stud nut. Remove control arm-to-frame nuts. Remove control arm.

To install, reverse removal procedure. Ensure front indexing hole in lower control arm shaft aligns with crossmember attaching stud.

Bushing Replacement (G10/1500-20/2500 Except 20/2500 W/6.2 Diesel)

1. Remove lower control arm. See «LOWER CONTROL ARM»(/gmc/magnavan-g3500/1985-1993/remont/suspension-front/#suspension-front-2wd) under REMOVAL & INSTALLATION in this article. 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 ), Spacers (J-24435-2 and J-24435-6 ), Bushing Remover (J-24435-2 ) and Fixture (J-24435-7 ), remove front bushing.
4. To install bushing, use Bushing Installer (J-24435-4 ), Spacer (J-24435-6 ) and Fixture (J-24435-7 ), install front bushing. Stake front bushing in at least 2 areas.
5. Outer tube hole must be aligned so it faces front or forward to the 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.

Bushing Replacement (G20/2500 W/6.2 Diesel)

1. Remove lower control arm. See «LOWER CONTROL ARM»(/gmc/magnavan-g3500/1985-1993/remont/suspension-front/#suspension-front-2wd) under REMOVAL & INSTALLATION in this article. Remove nuts and washers from control arm shaft.
2. Use Control Arm Bushing Set (J-24435-A ) for bushing replacement. Using Bushing Removers (J-24435-1 and J-24435-3 ) and Fixture (J-24435-7 ), remove one bushing from control arm. Remove control arm shaft. Repeat procedure and remove remaining bushing.
3. To install bushings, use Bushing Installer (J-24435-4 and J-24435-5 ) and Fixture (J-24435-7 ). Install one bushing. Install control arm shaft and repeat procedure for remaining bushing installation. Install lower control arm.

1. Raise and support vehicle under frame with control arms hanging free. Remove wheel and tire assembly. Disconnect shock absorber and stabilizer bar bracket at lower control arm.
2. Place floor 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 the inside of stabilizer bar and on the outside of shock absorber.
3. Remove lower control arm "U" bolt nuts and washers. Lower control arm. Remove grease zerks. Remove bushing nuts and lower control arm shaft from control arm. Remove seals which are located between bushing and lower control arm shaft.
4. To install, slide new seal onto each end of upper control arm shaft. Install shaft into upper control arm. Adjust shaft until centered in control arm, then tighten bushing nuts to specification. (Scheme 6) 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. Tighten all fasteners to specification. Check wheel alignment.

Scheme 6

CROSSMEMBER & SUSPENSION UNIT

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

1. Disconnect negative battery cable. Raise and support vehicle. Remove front wheel and tire assemblies. Disconnect front brake hose clip from each upper control arm.
2. Support front of vehicle with jack stands at frame side rails and lower front with hoist. Clean area around front brake hose fittings. Remove hoses from brake calipers and plug openings.
3. Disconnect tie rod ends from steering knuckles. Disconnect front stabilizer bar (if equipped) and shock absorbers from lower control arms. Remove brake line clip bolts from front suspension crossmember. On "R" models, clip is located under right side engine mount support bracket. 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: Engine must be supported prior to 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.

"P" Series

TORQUE SPECIFICATIONS

"G" Series

TORQUE SPECIFICATIONS

See also:
• WHEEL BEARING ADJUSTMENT
• UPPER CONTROL ARM BUSHINGS