Chevrolet Silverado / GMC Sierra. Service manual — part 837

4. Flush the oil cooler and pipes with water and solution for 2 minutes. During this flush,

attach the shop air supply 825 kPa (120 psi) to the flushing system feed air valve (2) located
on the J 35944-A for 3-5 seconds at the end of every 15-20 second interval to create a
surging action.

5. Release the trigger (8) and turn the J 35944-A water supply valve (1) to the OFF position.

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.

2. Repeat steps 3 and 4 of the INITIAL FLUSH procedure.

3. Release the trigger (8) of the J 35944-A and allow water only to rinse the oil cooler and

pipes for 1 minute.

4. Turn the J 35944-A water supply valve (1) to the OFF position and turn OFF the water

supply at the faucet.

5. Attach the shop air supply to the flushing system feed air valve (2) on the J 35944-A and

blow out the water from the oil cooler and pipes. Continue until no water comes out of the
discharge hose (5).

FLOW CHECK

be captured in a suitable container, preferably with a lid.

2008 Chevrolet Silverado 1500

2008 TRANSMISSION Automatic Transmission - Allison - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &

Silverado

Fig. 7: Connecting Return Pipe, Top Connector, To Discharge Hose
Courtesy of GENERAL MOTORS CORP.

1. Disconnect both hoses from the oil cooler pipes. Connect the oil cooler feed pipe, bottom

connector, to the transmission. Connect the return pipe, top connector, to the discharge hose
(5). This will require the use of J-44835-1 . Clip the discharge hose (5) onto an empty oil
drain container.

2. Confirm the transmission is filled with automatic transmission fluid.

3. Start the engine with the transmission in PARK range and run for 5 seconds at 2,400 RPM.

A minimum of 2.2 L (2.3 quarts) must be discharged during this 5 second run time.

If fluid flow is greater than 2.2 L (2.3 quarts) in 5 seconds at 2,400 RPM, go to step 4.

If fluid flow is less than 2.2 L (2.3 quarts) in 5 seconds at 2,400 RPM, 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. Start

2008 Chevrolet Silverado 1500

2008 TRANSMISSION Automatic Transmission - Allison - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &

Silverado

the engine with the transmission in PARK range and run for 5 seconds at 2,400 RPM.
A minimum of 2.2 L (2.3 quarts) must be discharged during this 5 second run time at
2,400 RPM. Do the following according to the flow rate:

Insufficient feed flow: Inspect the transmission.

Sufficient feed flow: Inspect the oil cooler return pipe, the oil cooler located in
the radiator, and the auxiliary oil cooler.

4. Remove the discharge hose (5), connect the cooler feed and return pipes to the transmission

and fill the unit to the proper fluid level. Inspect the transmission oil cooler pipe
connections at the radiator, the auxiliary cooler and the transmission for leaks.

CLEAN-UP

1. Disconnect the water supply hose (7) from the J 35944-A and bleed any remaining air

pressure from the flusher tank (4).

2. Remove the fill cap (9) from the J 35944-A and return any unused flushing solution to its

container. Rinse the J 35944-A with water. Do not store the J 35944-A with flushing
solution in it.

3. After every third use, clean the J 35944-A as described in the instructions included with the

tool.

4. Dispose of any waste water/solution and transmission fluid in accordance with local

regulations.

BUSHING AND MATING SHAFT INSPECTION

Any of the following bushing conditions require replacement of the bushing and/or housing:

Discoloration due to heat distress

Misalignment or displacement of bushing as a result of spinning in housing

Medium to heavy scoring that can be easily detected with fingernail. Light scoring is a
normal condition.

Debris embedded into the bushing lining material

IMPORTANT: Proper bushing and corresponding mating shaft inspection

should be performed before replacing the bushing, shaft, and in
some cases, the component which houses the bushing.
Thoroughly clean and dry the bushing and shaft surfaces before
inspecting for damage.

2008 Chevrolet Silverado 1500

2008 TRANSMISSION Automatic Transmission - Allison - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &

Silverado

Obvious damage, including excessive and uneven wear

Excessive polishing. Minor polishing of the bushing is an indication of normal wear and
does not require replacement.

Any of the following conditions require replacement of the bushing's mating shaft:

Discoloration due to heat distress

Rough surface finish that can be easily detected with finger

Obvious shaft abnormalities, including warping or uneven surfaces

Obvious damage or cracking

EXCESSIVE SLIPPAGE AND CLUTCH CHATTER

Condition

Action

Incorrect speed sensor readings

See speed sensor DTCs.

Incorrect fluid level

Correct the fluid level. Refer to Transmission
Fluid Check.

Main pressure low

Repair the transmission.

TCC clutch not applied

Inspect the torque converter clutch system
wiring, pressure, and controls. Repair as
necessary.

Ranges 1, 2, 3, 4 Only

1-2-3-4 clutch slipping, leaks at rotating
clutch seals, leaks at piston seals, 1-2-3-4
clutch plates worn

Inspect the 1-2-3-4 clutch plates, and piston
and rotating seals. Replace/rebuild as
necessary.

Ranges 4, 5, 6 Only

4-5-6 clutch slipping, leaks at rotating clutch
seals, leaks at piston seals, 4-5-6 clutch
plates worn

Inspect the 4-5-6 clutch plates, and piston and
rotating seals. Replace/rebuild as necessary.

Ranges 3, 5, R Only

3rd, 5th and Reverse clutch slipping, leaks
at piston seals, 3rd, 5th and Reverse clutch
plates worn

Inspect the 3rd, 5th and Reverse clutch plates
and piston seals. Replace/rebuild as necessary.

Range 2, 6 Only

2-6 clutch slipping, leaks at piston seals, 2nd
clutch plates worn

Inspect the 2-6 clutch plates and piston seals.
Replace/rebuild as necessary.

Ranges 1, R Only

2008 Chevrolet Silverado 1500

2008 TRANSMISSION Automatic Transmission - Allison - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &

Silverado