Before attempting any repair on a 545RFE automatic transmission, check for Diagnostic Trouble Codes with the scan tool.Transmission malfunctions may be caused by these general conditions:Poor engine performanceImproper adjustmentsHydraulic malfunctionsMechanical malfunctionsElectronic malfunctionsDiagnosis of these problems should always begin by checking the easily accessible variables: fluid level and condition, gearshift cable adjustment. Then perform a road test to determine if the problem has been corrected or if more diagnosis is necessary. If the problem persists after the preliminary tests and corrections are completed, hydraulic pressure checks should be performed.