Wheel Alignment Specifications & Procedures - Except "s" Series GMC Cab & Chassis S15

PRE-ALIGNMENT INFORMATION

Note. A normal shim pack will leave at least 2 threads of bolt exposed beyond the nut. Difference between front and rear shim packs must not exceed .40" (10.32 mm) on "S", "T" and "M" series or .30" (7.62 mm) on "C" and "G" series. On "C" and "G" series, ensure front shim pack is at least .10" (2.52 mm) thick.

1. On all models except "K" series, caster and camber can be adjusted in 1 operation. On "K" series, caster and camber is designed into the front axle assembly and is not adjustable.
2. On all models, check and set wheel alignment with vehicle in its normally loaded condition. Trucks which are consistently operated with heavy loads should have toe-in adjusted with truck under heavy load.
3. On "C" and "G" series, in order to gain access to shim packs, jack up frame to raise wheel off ground. This will allow upper control arm to drop down far enough to use a socket on the nuts and permit shim adjustment. On G30 and C20/30 models (with 7/8" nut), remove upper control arm bumper.
4. On all models, toe-in must be checked AFTER changing camber and/or caster. Before adjusting caster and/or camber angles, raise and release front bumper twice to allow vehicle to return to its normal height. See RIDE HEIGHT article.
5. On "C" and "G" series, the caster specifications are given with a frame angle of zero. Therefore, it will be necessary to know the angle of the frame (whether "up" in rear or "down" in rear) before a corrected caster reading can be determined. See «CASTER ANGLE DETERMINATION»(/gmc/cab-chassis-s15/1985-1988/remont/wheel-alignment/#wheel-alignment-specifications-procedures-except-s-series__caster-angle-determination-c-g) .
6. Specifications must be adjusted when applying them to vehicles with any frame angle other than zero. Camber and toe can be read "as is" from the alignment equipment.

CASTER ANGLE DETERMINATION ("C" & "G" SERIES)

1. With vehicle on level surface, determine frame angle using bubble protractor or inclinometer. Determine caster angle reading from the alignment equipment.
2. To determine an actual (corrected) caster angle with various frame angles and caster angle readings from the alignment equipment, one of the following rules applies: A "down in rear" frame angle must be subtracted from a positive caster angle reading. (Scheme 4), Example A. An "up in rear" frame angle must be added to positive caster angle reading. (Scheme 4), Example B. A "down in rear" frame angle must be added to a negative caster angle reading. (Scheme 4), Example C. An "up in rear" frame angle must be subtracted from a negative caster angle reading. (Scheme 4), Example D.
3. The dimension "BC" is measured 90° from lower surface of crossmember to inboard rear corner of jounce bumper bracket. (Scheme 4), View A. Using dimension "BC" and the appropriate CASTER, CAMBER & TOE-IN table, find the recommended caster angle.
4. If an actual (corrected) caster angle (step 2) does not correspond to a recommended caster angle (step 3) within F1°, make necessary shim changes to bring actual (corrected) caster angle in line with recommended caster angle.

Determining Caster Angle ("C" Series Shown, "G" Series Similar). Scheme 4

2WD Models - "C" Series

Determine caster angle from alignment machine and adjust as necessary. To decrease positive caster, transfer 1 or more shims from between rear upper control arm retaining bolt and frame to front retaining bolt and vise versa. (Scheme 5) If a normal shim pack will not bring vehicle within specifications, check for damaged control arms and related parts.

4WD Models - "K" Series

Determine caster angle from alignment machine and correct (if adjustable) as necessary. To adjust caster on "T" models, loosen upper control arm-to-frame mounting nuts. Rotate either cam (depending on adjustment needed) by rotating bolt head. To increase positive caster, move front cam lobe inward and rear cam outward and vise versa. If vehicle front end alignment specifications are not within limits, check for damaged control arms and related parts.

CAMBER - PRELIMINARY INFORMATION

Note. Adding an equal number of shims at both front and rear of cross shaft will decrease positive camber. By adding or subtracting equal amounts of shims, camber may be corrected without affecting caster.

Determine camber angle from alignment machine and adjust as necessary. Camber is changed by adding or subtracting shims from between upper control arm shaft and frame bracket. Adding an equal number of shims at both front and rear of cross shaft will decrease positive camber and vice versa. (Scheme 5) If a normal shim pack will not bring vehicle within specifications, check for damaged control arms and related parts.

Determine camber angle from alignment machine and correct (if adjustable) as necessary. To adjust camber on "T" models, loosen upper control arm-to-frame nuts. To increase positive camber, move both front and rear cam lobes inward. If alignment specification is not within limits, check for damaged control arms and related parts.

Adjusting Caster & Camber By adding or subtracting equal amounts of shims, camber may be corrected without affecting caster. Scheme 5

TOE-IN

Note. Toe-in can be increased or decreased by turning the threaded sleeve to change the length of the tie rods. When tie rods are mounting ahead of the steering knuckle, they must be decreased in length in order to increase toe-in.

1. Determine toe-in and adjust as necessary. Inspect tie rod adjuster sleeve clamp bolts and nuts for rust. If in good condition, loosen nuts and bolts. If excessively rusted, measure nut removal torque after breakaway. If more than 7 ft. lbs. (9 N.m), replace nut(s) and bolt(s).
2. Apply penetrating oil to adjuster sleeve and clamps, then rotate sleeve until free on tie rods. Center steering wheel and lock in position with steering wheel holder.
3. With clamp bolts and nuts of each adjusting sleeve loose, turn adjuster sleeves to obtain proper toe-in adjustment. After adjustment, check that the number of threads showing on each end of sleeve are equal (within 3 threads) and tie rod end housings are at right angles to steering arm.
4. Position clamps with bolt centerlines horizontal (within 60° of each other). Ensure adjuster sleeve slot is not within clamp jaws. With clamps between and clear of dimples, tighten clamp bolts and nuts.
5. Clamp ends may touch when nuts are tightened to specification but gap adjacent to adjuster sleeve must not be less than .0050" (.127 mm). Replace clamp and/or sleeve if not to specification.

REAR WHEEL & AXLE HOUSING ALIGNMENT

1. If rear tire wear indicates that axle housing may be bent, check alignment. Back vehicle squarely onto an alignment machine. Compensate for wheel runout the same as for checking front wheel toe-in. NOTE: Due to the fact the vehicle is backed onto alignment machine, the actual toe-out will be read on the scale as toe-in. If tram (scuff) gauge is used to check toe-out, disregard this note.
2. Check camber. Camber reading should be 3° negative to 5° positive. Check toe-in. Proper toe-in is 0° to .05° (0" to 1/16"). If vehicle is not within specification, check and straighten frame and/or related components as necessary.

Note. Equipment used to straighten frame must allow rechecking of camber and toe-in without removing axle housing from vehicle.

CASTER, CAMBER & TOE-IN CALCULATION - G30 SERIES

CASTER, CAMBER & TOE-IN CALCULATION (G30 SERIES) (1)

CASTER, CAMBER & TOE-IN CALCULATION - G10/20 SERIES

CASTER, CAMBER & TOE-IN CALCULATION (G10/20 SERIES) (1)

CASTER, CAMBER & TOE-IN CALCULATION - K10/30 SERIES

CASTER, CAMBER & TOE-IN CALCULATION (K10/30 SERIES) (1) (2)

CASTER, CAMBER & TOE-IN CALCULATION - C10 SERIES

CASTER, CAMBER & TOE-IN CALCULATION - C10 SERIES (1)

CASTER, CAMBER & TOE-IN CALCULATION - C20/30 SERIES

CASTER, CAMBER & TOE-IN CALCULATION - C20/30 SERIES (1)

CASTER, CAMBER & TOE-IN ALIGNMENT SETTING TOLERANCE

CASTER, CAMBER & TOE-IN ALIGNMENT SETTING TOLERANCE (1)

WHEEL ALIGNMENT SPECIFICATIONS - C10

WHEEL ALIGNMENT SPECIFICATIONS (C10)

WHEEL ALIGNMENT SPECIFICATIONS - C20/30

WHEEL ALIGNMENT SPECIFICATIONS (C20/30)

WHEEL ALIGNMENT SPECIFICATIONS - K10/20/30

WHEEL ALIGNMENT SPECIFICATIONS (K10/20/30)

TORQUE SPECIFICATIONS

TORQUE SPECIFICATIONS

See also:
• CASTER ANGLE DETERMINATION