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3. Examine the drained fluid for evidence of engine coolant. 4. Examine the drained fluid for evidence of metal. Metal particles in the fluid, other than minute particles normally trapped in the oil filter, indicate internal transmission damage. 5. Metal contamination requires complete transmission disassembly. 6. Clean all internal and external hydraulic circuits, cooler, and all other areas where the particles could lodge. Refer to Transmission Fluid Cooler Flushing and Flow Test. LINE PRESSURE CHECK immediate action. Failure to clean or replace all contaminated NOTE: Flush the transmission cooling system and inspect for
2008 Chevrolet Silverado 1500 2008 TRANSMISSION Automatic Transmission - Allison - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
Fig. 1: Transmission Pressure Gage Checking main line pressure helps to determine if a transmission malfunction is due to a 1. Remove the oil pressure tap plug. Refer to Automatic Transmission Fluid Pressure Test Hole Plug Replacement. 2. Install J 45056 pressure test adapter fitting prior to connecting the oil pressure gage. CAUTION: Keep the brakes applied at all times in order to prevent unexpected vehicle motion. Personal injury may result if the
2008 Chevrolet Silverado 1500 2008 TRANSMISSION Automatic Transmission - Allison - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
3. All transmission fluid level and pressure checks must be made at normal operating temperatures 71-93°C (160-200°F) sump; 82-104°C (180-220°F) converter-out. Check the 4. Connect a 0-2070 kPa (0-300 PSI) oil pressure gage to the pressure test adapter fitting. Use the scan tool to check the engine RPM. Refer to Line Pressure for pressure level 5. With the brakes applied, record the line pressure values at 600 RPM engine speed in NEUTRAL and REVERSE range. The transmission will be in converter mode, torque 6. With the brakes applied, record the line pressure values with the engine running at 2,100 RPM in NEUTRAL. The transmission will be in converter mode, torque converter clutch 7. With the brakes applied, use the following scan tool settings to check pressures in FIRST through FIFTH gear ranges at 600 RPM. The transmission will be in converter mode, torque 1. Select F0: Diagnostics and press ENTER. 2. Select Model Year. 3. Select LDTrk, MPV, Incomplete. 4. Select F0: Powertrain, press ENTER. 5. Select Engine size, press ENTER. 6. Select 6 Speed Automatic, press ENTER. 7. Select F2: Special Functions, press ENTER. 8. Select F1: Transmission Output Controls. 9. Select Shift transmission. This will allow the technician to shift the transmission and check line pressure in each forward gear range. 8. Compare the data recorded to the line pressure specifications. Refer to Line Pressure . 9. Disconnect the oil pressure gage and remove the J 45056 pressure test adapter fitting. 10. Install the oil pressure tap plug again. Refer to Automatic Transmission Fluid Pressure Test Hole Plug Replacement. OBTAINING DIAGNOSTIC TROUBLE CODES A microcomputer controls the transmission by receiving and processing signals from various
2008 Chevrolet Silverado 1500 2008 TRANSMISSION Automatic Transmission - Allison - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
park/neutral position (PNP) switch provide operator input to the TCM. Other data sent to the To obtain transmission diagnostic trouble codes (DTCs), install the scan tool and follow the menu 1. From the title screen, press ENTER. 2. Select F0: Diagnostics. Press ENTER. 3. Select Model Year. Press ENTER. 4. Select LDTrk, MPV, Incomplete. Press ENTER. 5. Select Product Make, i.e. (C) Chevrolet Truck, (T) GMC Truck. Press ENTER. 6. Select Product Line, i.e. (C) or (K). Press ENTER. 7. Select F0: Powertrain. Press ENTER. 8. Select Engine size. Press ENTER. 9. Select 6 Speed Automatic. Press ENTER. 10. Select F0: Diagnostic Trouble Codes (DTC). Press ENTER. 11. Select F1: DTC (s) (Transmission). Press ENTER. 12. Select F0: DTC Information. Press ENTER. 13. Select F0: DTC Info. Press ENTER. CLUTCH TEST Clutch Test allows a technician to manually select each of the 6 forward ranges with the vehicle IMPORTANT: Before clearing the DTC, use the scan tool in order to record the Freeze Frame and Failure Records for reference. The Clear Info
2008 Chevrolet Silverado 1500 2008 TRANSMISSION Automatic Transmission - Allison - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
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