M I I A TX05 0277 RPO DEFINITIONS 1 I 1 A GT5 REAR AXLE 4 10 RATIO V GU4 REAR AXLE 3 08 RATIO A I I GU5 REAR AXLE 3 23 RATIO wi GU6 REAR AXLE 3 42 RATIO 1 1 JA4 BRAKE SYSTEM POWER FRT DISC REAR DRUM CAST IRON ANTILOCK FRT REAR WHEEL JM4 BRAKE SYSTEM POWER FRT DISC REAR DRUM CASTIRON ANTILOCK REAR WHEEL 3 1991 GENERAL MOTORS SERVICE PARTS OPERATIONS LT TRUCK 52M 5 000 GROUP 5 12 1 91