HIGH/LATE UPSHIFTS DIESEL LOW VAC./TRANS. MODULATOR

COMMENTS REGARDING HIGH OR LATE UPSHIFTS IN THE MODEL DESCRIBED ABOVE, MAY BE CAUSED BY A POOR VACUUM SIGNAL TO THE TRANSMISSION. DURING THE EARLY 1982 PRODUCTION, THE ENGINE END OF THE TRANSMISSION MODULATOR VACUUM PIPE WAS CHANGED. THE REDUCTION IN THE PIPE DIAMETER RESULTED IN ELIMINATING RESONANCE IN THE VACUUM REGULATOR VALVE, INCREASING THE LIFE OF THE VALVE. WHEN DIAGNOSING A VEHICLE COMPLAINT, THE FOLLOWING PROCEDURE IS RECOMMENDED: 1. REMOVE THE VACUUM HOSE FROM THE MODULATOR PIPE (HOSE FROM PIPE TO VALVE). 2. CHECK FOR THE CORRECT MODULATOR PIPE. THE PIPE, P/N 14054204, SHOULD BE 5/32 I.D. AND APPROXIMATELY 5 INCHES LONG. REFER TO FIGURE 1 VIEW B. 3. REPLACE WITH CORRECT MODULATOR PIPE IF REQUIRED. 4. CHECK FOR PROPER VACUUM PUMP OUTPUT. WHEN HOOKED UP TO A VACUUM GAGE, THE PUMP SHOULD PRODUCE APPROXIMATELY 70KPA (21 IN.HG.) OF VACUUM. IF SUFFICIENT VACUUM IS NOT BEING PRODUCED, DETERMINE CAUSE AND CORRECT. 5. CHECK FOR THE CORRECT VACUUM REGULATOR VALVE, P/N 14057219, AS PER BULLETIN NO.83-B-32. SET THE VALVE TO THE CORRECT SETTING OF 27KPA (8 IN.HG.) AS PER SERVICE MANUAL PROCEDURE (606-2). IF THE SETTING OF 27KPA IS NOT OBTAINABLE. THE VALVE SHOULD BE REPLACED.

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.