Automatic Transmission - Servicing - Allison: Other Chevrolet Silverado 2500

Transfer Case

Check level at every oil change. Manufacturer does not provide fluid change interval.

Checking Level (Cold)

Note. The fluid level rises as fluid temperature increases. Do not fill above the "COLD CHECK" band if the transmission fluid is below normal operating temperatures. If the fluid level is within the "COLD CHECK" band, the transmission may be operated until the fluid is hot enough to perform a "HOT RUN" check. If the fluid level is not within the "COLD CHECK" band, add or drain as necessary to bring it to the middle of the "COLD CHECK" band. Always check the fluid level at least twice using the procedure described above. Consistent readings are important to maintaining proper fluid level. If inconsistent readings persist, check the transmission vent assembly to be sure that it is clean and unclogged. If readings are still inconsistent, contact your nearest Allison dealer.

Note. The purpose of the cold check is to determine if the transmission has enough fluid to be operated safely until a hot check can be made.

1. Bring the vehicle to a complete stop on a level surface using the service brakes. Ensure the engine is at low idle (500-800 RPM). With the service brakes applied, put the transmission in Park position.
2. Engage the park pawl by slowly releasing the service brakes. The vehicle may move slightly as the pawl engages. Apply the parking brake and make sure it is properly engaged.
3. Run the engine for at least one minute. Apply the service brakes and shift to Drive, then to Neutral, and then shift to Reverse to fill the hydraulic system. Ensure the engine is at low idle (500-800 RPM).
4. With the service brakes applied, place the transmission in the Park position. Engage the park pawl by slowly releasing the service brakes. The vehicle may move slightly as the pawl engages.
5. With the engine running, remove the fluid level indicator from the fill tube and wipe the indicator clean insert the fluid level indicator into the fill tube and remove. Check the fluid level reading.
6. Repeat the check procedure to verify the reading. Perform a hot check at the first opportunity after the normal operating sump temperature of 160-200°F (71-93°C) is reached.

Checking Level (Hot)

Note. The fluid must be hot to ensure an accurate check. The fluid level rises as temperature increases.

1. Operate the transmission in Drive range until normal operating temperature is reached. Normal operating temperature is indicated by a sump temperature of 160-200°F (71-93°C) or a converter-out temperature of 180-220°F (82-104°C). If a transmission temperature gauge is not present, check fluid level when the engine water temperature gauge has stabilized and the transmission has been operated under load for at least one hour.
2. Bring the vehicle to a complete stop on a level surface using the service brake. Ensure the engine is at low idle RPM (500-800 RPM). With the service brakes applied, put the transmission in the Park position. Engage the park pawl by slowly releasing the service brakes. The vehicle may move slightly as the pawl engages.
3. Apply the parking brake and make sure it is properly engaged. With the engine running, remove the fluid level indicator from the fill tube and wipe the indicator clean. NOTE: Always check the fluid level at least twice using the procedure described above. Consistent readings are important to maintaining proper fluid level. If inconsistent readings persist, check the transmission vent assembly to ensure it is clean and unclogged. If readings are still inconsistent, contact your nearest Allison distributor or dealer.
4. Insert the fluid level indicator into fill the tube and remove. Check fluid level reading. Repeat the check procedure to verify the reading. NOTE: Safe operating level is within the "HOT RUN" band on the fluid level indicator. The width of the "HOT RUN" band represents approximately 1.06 qts. (1.0L) of fluid at normal operating sump temperature.
5. If the fluid level is not within the "HOT RUN" band, add or drain as necessary to bring the fluid level to within the "HOT RUN" band.

Manufacturer recommends AUTO-TRAK II fluid (GM P/N 12378508).

The following refill capacities given are approximate. Correct fluid level should always be determined by marks on dipstick, rather than amount of fluid added. See CHECKING FLUID LEVEL & CONDITION (TRANSMISSION) . DO NOT overfill. See TRANSMISSION FLUID CAPACITIES table.

TRANSMISSION FLUID CAPACITIES

The following refill capacities given are approximate. Correct fluid level should always be determined by level of fluid at fill hole, rather than amount of fluid added. See CHECKING FLUID LEVEL (TRANSFER CASE) . DO NOT overfill. See TRANSFER CASE FLUID CAPACITIES table.

TRANSFER CASE FLUID CAPACITIES

Note. Transmission is equipped with an external control main "spin on" filter, which can be replaced without draining the transmission fluid from the pan. The control main filter is to be changed after the first 5000 miles. Failure to change the filter at this interval may cause DTC P0701 and other pressure switch DTCs to set.

Note. Transmission is also equipped with an internal fluid pick up filter screen that can be serviced only by removing the oil pan. See INTERNAL FILTER REPLACEMENT .

1. Remove drain plug (6) and drain plug seal (5). (Scheme 340) Drain the transmission fluid into a suitable container.
2. Inspect the drained fluid. See «CHECKING FLUID CONDITION»(ref-138386-S14807443272002041000000) under CHECKING FLUID LEVEL & CONDITION (TRANSMISSION).
3. Remove filter (4) by rotating it in the counterclockwise direction. (Scheme 340) Remove the magnet (2) from the filter attachment tube (1) in the converter housing or from the top of the control main filter (3).
4. Clean any metal debris from the magnet. Presence of any metal pieces larger than dust may indicate that transmission replacement or overhaul is required.
5. Reinstall the magnet (2) onto the filter attachment tube (1) which is in the converter housing. (Scheme 340) Lubricate the gasket (3) on the control main filter with transmission fluid. Install, by hand, the control main filter (4) until the gasket on the control main filter touches the converter housing. Turn the filter ONE FULL TURN ONLY after gasket contact.
6. Reinstall the drain plug (6) and drain plug seal (5). Tighten the drain plug to specification. See «TORQUE SPECIFICATIONS»(ref-138386-S35372756022002040900000).
7. Fill transmission with appropriate fluid to proper level. See «RECOMMENDED FLUIDS»(ref-138386-S41518425362002040900000) and «FLUID CAPACITIES»(ref-138386-S27145948502002040900000). NOTE: DTC P0701 may often set following fluid service. Cycling the ignition clears the code and allows Drive or Reverse range to be attained. Cycle the ignition until Drive or Reverse range is attained.
8. Check the transmission fluid level. See «CHECKING FLUID LEVEL & CONDITION (TRANSMISSION)»(ref-138386-S39749265502002040900000).

Scheme 340

Remove fill and drain plugs from transfer case. After fluid has drained, reinstall drain plug and tighten to specification. See TORQUE SPECIFICATIONS . Fill transfer case with appropriate fluid to proper level. See RECOMMENDED FLUIDS and FLUID CAPACITIES . Install transfer case fill plug and tighten to specification.

Preparation

1. After the repair or replacement transmission is installed in the vehicle, do not reconnect the oil cooler pipes.
2. Remove the fill cap (9) on the Transmission Oil Cooler and Line Flusher (J-35944-A) and fill the flusher tank (4) with 20 oz. (0.6L) of flushing fluid using the measuring cup (6). DO NOT overfill. Install the fill cap (9) on the transmission oil cooler and line flusher and pressurize the flusher tank (4) to 80-100 psi, using the shop air supply at the tank air valve (9). (Scheme 341)
3. Connect the transmission oil cooler and line flusher discharge hose (5) to the oil cooler return pipe (top connector). Clip the discharge hose (5) onto the oil drain container. Attach the transmission oil cooler and line flusher to the undercarriage of the vehicle with the hook provided, and connect the flushing system feed supply hose (3) from the transmission oil cooler and line flusher to the oil cooler feed pipe (bottom connector).
4. With the water supply valve (1) on the transmission oil cooler and line flusher in the OFF position, connect the water supply hose (7) from the transmission oil cooler and line flusher to the water supply at the faucet. (Scheme 341)and (Scheme 342). Turn ON the water supply at the faucet.

Scheme 341

Scheme 342

Flow Check

1. Disconnect both hoses from the oil cooler pipes. Connect the oil cooler feed pipe (vertical/top connector) to the transmission and the return pipe (horizontal/bottom connector) to the discharge hose (5). Clip the discharge hose (5) onto the empty oil drain container. see scheme 7
2. Confirm the transmission is filled with ATF. See «CHECKING FLUID LEVEL & CONDITION (TRANSMISSION)»(ref-138386-S39749265502002040900000). Start the engine with the transmission in Park range and run for 30 seconds. A minimum of 2 qts. (1.9L) must be discharged during this 30-second run time. If fluid flow is greater than 2 qts. (1.9L) in 30 seconds, go to next step. If fluid flow is less than 2 qts. (1.9L) in 30 seconds, perform the following diagnosis: Disconnect the oil cooler feed line at the radiator. Connect the discharge hose (5) to the cooler feed line. Clip the discharge hose (5) to the empty oil drain container. see scheme 7 Start the engine with the transmission in Park range and run for 30 seconds. A minimum of 2 qts. (1.9L) must be discharged during this 30-second run time. Perform the following according to the flow rate: Insufficient feed flow: inspect the transmission. Sufficient feed flow: inspect the oil cooler return pipe and the oil cooler (and auxiliary cooler, if equipped).
3. Remove the discharge hose (5), reconnect the cooler feed and return pipes to the transmission and refill the unit to the proper fluid level. Inspect the transmission oil cooler pipe connections at the radiator, the auxiliary cooler (if equipped) and the transmission for leaks.

Clean-up

Disconnect the water supply hose (7) from the transmission oil cooler and line flusher and bleed any remaining air pressure from the flusher tank (4). (Scheme 341) Remove the fill cap (9) from the transmission oil cooler and line flusher and return any unused flushing solution to its container. Rinse the transmission oil cooler and line flusher with water. DO NOT store the transmission oil cooler and line flusher with flushing solution in it. After every 3rd use, clean the transmission oil cooler and line flusher as described in the instructions included with the tool. Dispose of any waste water/solution and transmission fluid in accordance with local regulations.

ON-VEHICLE REPAIRS

Various components may be serviced without transmission removal, depending on application. For servicing of these components, see appropriate component under ADJUSTMENTS and/or REMOVAL & INSTALLATION . For additional information on testing electrical components, see appropriate DIAGNOSIS article in AUTOMATIC TRANSMISSIONS.

PARK/NEUTRAL POSITION SWITCH

Note. Tools required: Park/Neutral Position Switch Alignment Tool (J-41364-A).

1. Disconnect the external wiring harness from the PNP switch (5). Disconnect the shift linkage/cable from the shift lever at the transmission. Use a wrench (1) to keep the shift lever (2) from rotating. Remove the nut (3) from the end of the selector shaft (4). (Scheme 343) Carefully remove the shift lever (2) from the selector shaft (4). Loosen the 2 bolts (6) so PNP switch may be rotated with slight effort.
2. Place the selector shaft in the Neutral position as follows: Place a wrench on the selector shaft flats and rotate the shaft to its furthest clockwise position. (Scheme 343) Rotate the selector shaft counter clockwise 2 detents.
3. Position the PNP switch alignment tool over the selector shaft (3) so the 2 tabs on the tool engage the 2 slots in the PNP switch (2) just outside the selector shaft. (Scheme 344) Rotate the PNP switch (2) until the single tab (1) at the other end of the tool engages the single slot at the top of the PNP switch.
4. Hold the tool in engagement with the PNP switch to maintain alignment of the PNP switch with the selector shaft. Tighten the 2 bolts (4) to specification. See «TORQUE SPECIFICATIONS»(ref-138386-S35372756022002040900000). CAUTION: Do not drive the selector lever onto the selector shaft. Do not use an impact wrench in order to tighten the selector lever nut. Hold the lever with a wrench while tightening the nut. Failure to follow these instructions may result in transmission damage.
5. Reinstall shift lever (2). Install nut (3), by hand, on the end of selector shaft (4). Use a wrench (1) to keep the shift lever from rotating. (Scheme 343) Tighten nut (3) to 18 ft. lbs. (24 N.m). Reconnect the shift selector linkage/cable to the shift lever (2). Connect the external wiring harness connector to the PNP switch.

Scheme 343

Scheme 344

SHIFT CABLE

1. Ensure the gearshift lever and the transmission manual shaft lever are in the Park position. Raise the vehicle. Pull back the white plastic cover (1) on the center connector. (Scheme 345)
2. Pull up on the center tabs of the lock button (2). (Scheme 346) NOTE: This step must be performed correctly to avoid a misadjusted cable. Do not grasp the shift cable end (2) during this procedure.
3. Release the shift cable end (2) and allow the Blue spring to tension/adjust the shift cable system. (Scheme 347) Pull the White cover (3) on the shift cable end (1) back.
4. Push the Natural colored lock button (2) down to engage the locking teeth on the shift cable end (1). (Scheme 348) Release the White cover (1). (Scheme 349)
5. Verify the White cover (1) conceals the Natural colored lock (2). (Scheme 350) If the White cover (1) does not conceal the Natural colored lock (2), the shift cable must be readjusted.
6. Test the transmission for proper shift operation. If all of the gear positions cannot be achieved, the shift cable must be readjusted.

Scheme 345

Scheme 346

Scheme 347

Scheme 348

Scheme 349

Scheme 350

CONTROL MAIN FILTER ATTACHMENT TUBE

Note. Do not drain the fluid if only the control main filter attachment tube is being replaced.

CONTROL VALVE BODY

Note. Tools required: Wiring Harness Connector Remover (J-44257) and Internal Wiring Harness Installer (J-44247).

FILLER TUBE & SEAL (8.1L)

Note. If the vehicle is equipped with a diesel engine, the transmission must be removed to service the fill tube and/or seal.

RANGE SELECTOR CABLE (COLUMN END)

Note. The range selector cable is a 2-piece cable assembly. The front half (column end) or rear half (transmission end) of the range selector cable can be removed without removing the other end/half of the range selector cable assembly.

RANGE SELECTOR CABLE (TRANSMISSION END)

Note. The range selector cable is a two piece cable assembly. The front half (column end) or rear half (transmission end) of the range selector cable can be removed without removing the other end/half of the range selector cable assembly.

SPEED SENSORS

Note. Transmission uses 3 speed sensors.