Suspension - Torsion Bar Adjustment
88chevy02GMC NUMBER: 88-T-57
GROUP: 3C - Front Suspension
DATE: January, 1988
CORPORATE
NUMBER: 863302
SUBJECT: TORSION BAR ADJUSTMENT
MODELS: 1988 K-1, 2, 3 MODELS
1988 K models which are intended for snow plow applications may require front suspension option F60. When F60 is ordered, the vehicle's base torsion bars are upgraded to the next higher rate bars to compensate for vehicle trim changes due to the extra weight of the snow plow assembly. Vehicles that were built with Z71 off road chassis package were equipped with F60 as part of the Z71 package. Some vehicles equipped with base level torsion bars may only require minor trim height changes to be adaptable for snow plow applications. Variations in the assembly plant build and torsion bar settings may allow for additional trim height changes which can be made by adjusting up the torsion bars. On vehicles built before the VIN breakpoints provided below, it is not recommended that the torsion bars be adjusted more than four or five times. Vehicles built after the breakpoints can be adjusted multiple times without detrimental effects on the adjustment mechanism. Those vehicles equipped with base level torsion bars requiring additional trim height beyond that which is attainable through a trim height adjustment must have the F60 torsion bars installed in place of the base bars. To determine which torsion bar is installed in the vehicle, the three digit code stamped on the
end of the bar must be noted. These three digits are the last digits of the part number, which can be found in the base production torsion bar chart listed below. To determine the correct F60 bar to be used, the part number from the base production torsion bar side of the chart must be cross referenced over to the corresponding F60 torsion bar on the right-half of the chart. When replacing or adjusting torsion bars, follow the procedure in Front Suspension and Axle, Section 3C of the 1988 C/K Service Manual, X-8731. The front suspension alignment specification for vehicles which have had F60 installed at the dealer level are provided in the following chart. Most vehicles which have F60 installed will not require caster and camber adjustments, however, toe-in must be set at 0 degrees at vehicle curb trim.
VIN Breakpoints:
Fort Wayne JZ 525340
Pontiac JE 518636
Oshawa J1 537366
Adjustment or replacement of torsion bars to compensate for vehicles not equipped with F60 (snow plow package) is not covered under the terms of the New Vehicle Warranty.
K TRUCK TORSION BAR USAGE
Service Setting at Curb Front Suspension Alignment All K Models with F60
K-10-20 and F60
Caster 1.6 +/- 1.0 degrees
(Degrees) A
Camber .5 +/- .50 degrees
(Degrees) A
Sum Toe 0 degrees B Degrees)
K-30 and F60
1.6 +/- 1.0 degrees A
.3 +/- .50 degrees A
0 degrees B
Caster angle must be corrected to level frame angle.
Note: Vehicle must be jounced three times to eliminate false geometry readings.
A - Left and right side to be equal within .50 degrees. B - Toe-in left and right side to be set equally per wheel and steering wheel must be held in straight ahead position within +/- 5.0 degrees.
Note: Service checking and setting at settled (Z) heights for vehicles equipped with F60 torsion bars are:
K-10-20 K-30
161 mm +/- 6 mm 151 mm +/- 6 mm