TORSION BAR ADJUSTMENT SPECIFICATIONS AND PART NUMBER. GMC Truck GMC K Pickup

TORSION BAR ADJUSTMENT

VEHICLES AFFECTED: 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 Manuals, ST-375-88 or X-8731. The front suspension alignment specification for vehicles which have had F60 installed at the dealer level are provided in the chart below. 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 Chevrolet JZ186298 GMC JZ525340 Pontiac Chevrolet JE153765 GMC JE518636 Oshawa Chevrolet J1199957 GMC J1537366

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

Base Production Torsion Bar F60 Torsion Bar K-10 K-10 Part Numbers Part Numbers Left Right Left Right ----------------------- ------------------- 15528951 15528952 15528955 15528956 15528955 15528956 15528959 15528960 15528959 15528960 15528963 15528964 15528963 15528964 Not Available

K-20-30 K-20-30 Left Right Left Right ------------------------ -------------------- 15528953 15528954 15528957 15528958 15528957 15528958 15528963 15528964 15528963 15528964 15528965 15528966 15528965 15528966 Not Available

Service Setting at Curb Front Suspension Alignment All K Models with F60

K-10-20 and F60 K-30 and F60 --------------- ------------ Caster 1.6 +/- 1.0 degrees 1.6 +/- 1.0 degrees (Degrees) A A

Camber .5 +/- .50 degrees .3 +/- .50 degrees (Degrees) A A

(Sum Toe 0 degrees B 0 degrees B Degrees)

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 with .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 ------- ---- 161mm +/- 6mm 151mm +/- 6mm

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.