Automatic Transmission - Servicing - Allison: Maintenance Chevrolet Silverado 2500

SERVICE INTERVALS

Note. Follow the Short Trip/City Maintenance Schedule if any one of these conditions is true for your vehicle: Most trips are less than 5-10 miles. This is particularly important when outside temperatures are below freezing. Most trips include extensive idling (such as frequent driving in stop and go traffic). Most trips are through dusty areas or off road frequently. Vehicle is frequently operated in dusty areas or off road. Vehicle is frequently used to tow a trailer or use a carrier on top of your vehicle. If the vehicle is used for delivery service, police, taxi or other commercial application.

Under severe driving conditions, change transmission fluid every 25,000 miles. Under normal driving conditions, change transmission fluid every 50,000 miles.

Checking Fluid Condition

Note. Transmission fluid must be changed whenever there is evidence of dirt or a high temperature condition. High temperature causes the transmission fluid to be discolored or to have a strong odor. Local conditions, severity of operation, or duty cycle may require more or less frequent fluid or filter change intervals. Cooler water may be contaminated by engine oil if equipped with an engine oil cooler. Ensure to locate the correct source of cooler water contamination.

1. Examine the drained fluid for evidence of dirt. Examine the drained fluid for evidence of water. Obvious water contamination of the transmission fluid or transmission fluid in the cooling water from the heat exchanger indicates a leak between the water and fluid areas of the cooler. Inspect and pressure test the cooler to confirm the leak. Replace leaking coolers.
2. Examine the drained fluid for evidence of engine coolant. 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. When this occurs, check the inside of the oil pan for excessive metal particles. See «INTERNAL FILTER REPLACEMENT»(ref-138386-S26214141642002041000000) . Metal contamination requires complete transmission disassembly. NOTE: Flush the transmission cooling system and inspect for restrictions following a transmission failure. Failure to repair or replace restricted oil cooling system components may result in premature transmission failure.
3. Clean all internal and external hydraulic circuits, cooler, and all other areas where the particles could lodge. See «OIL COOLER FLUSHING»(ref-138386-S30739942952002041000000) .

CHECKING FLUID LEVEL (TRANSFER CASE)

Remove fill plug. Check oil level. If oil level is even with bottom of fill plug opening, add appropriate lubricant as necessary. See RECOMMENDED FLUIDS .

Manufacturer recommends Dexron-III ATF.

OIL COOLER FLUSHING

Note. GM studies indicate that plugged or restricted transmission oil coolers and pipes cause insufficient transmission lubrication and elevated operating temperatures which can lead to premature transmission wear out. Many cases could have been prevented by following published procedures for transmission oil cooler flushing and flow checking. This procedure includes flushing and flow checking the auxiliary oil cooler, if equipped. GM requires that oil cooler flushing and flow checking be performed whenever a transmission is removed from the vehicle for service within warranty, including: Goodwin, SWAT, major overhaul, torque converter replacement and oil pump replacement.

Initial Flush

1. Turn the transmission oil cooler and line flusher water supply valve (1) to the ON position and allow water to flow through the oil cooler and pipes for 10 seconds to remove any remaining transmission fluid. (Scheme 337) If water does not flow through the oil cooler and pipes, the cause of the blockage must be diagnosed and the plugged component must be repaired or replaced. Continue with the cooler flushing and flow check procedure once the blockage is corrected.
2. Turn the transmission oil cooler and line flusher water supply valve (1) to the OFF position and clip the discharge hose (5) onto an appropriate container with a lid, to avoid splashback. (Scheme 338) Turn the transmission oil cooler and line flusher water supply valve (1) to the ON position and depress the trigger (8) to mix cooler flushing solution into the water flow. see scheme 4 Use the clip provided on the handle to hold the trigger (8) down. The discharge will foam vigorously when the solution is introduced into the water stream.
3. Flush the oil cooler and pipes with water and solution for 2 minutes. During this flush, attach the shop air supply of 120 psi to the flushing system feed air valve (2) located on the transmission oil cooler and line flusher for 3-5 seconds at the end of every 15-20 second interval to create a surging action.
4. Release the trigger (8) and turn the transmission oil cooler and line flusher water supply valve (1) to the OFF position.

Scheme 337

Scheme 338

Back Flush

1. Disconnect both hoses from the oil cooler pipes and then connect them to the opposite oil cooler pipe. This will allow the oil cooler and pipes to be back flushed. Repeat steps 2 and 3 of the INITIAL FLUSH procedure. Release the trigger (8) of the transmission oil cooler and line flusher and allow water only to rinse the oil cooler and pipes for one minute.
2. Turn the transmission oil cooler and line flusher water supply valve (1) to the OFF position and turn OFF the water supply at the faucet. see scheme 5 Attach the shop air supply to the flushing system feed air valve (2) on the transmission oil cooler and line flusher, and blow out the water from the oil cooler and pipes. Continue until no water comes out of the discharge hose (5).