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Home >> GMC >> 1991 >> Value Van 7.4 N >> Repair and Diagnosis (Single Page) >> Transmission >> Automatic Trans >> Automatic Transmission - Overhaul - 4L80-E >> Trouble Shooting >> Symptom Diagnosis >> Wrong Shift Points

Wrong Shift Points

Problem related to PCM or TCM signal inputs from TPS, speed sensors or pressure switch manifold. Faulty digital ratio adapter (2WD only). Possible trouble Code 21, 22, 24, 28 or 85. Wrong tire size, axle ratio or PROM.