NEW FLUID LEVEL INDICATORS AND NEW FLUID CHECK PROCEDURES

Subject: NEW FLUID LEVEL INDICATORS AND FLUID CHECK PROCEDURES

Model and Year: 1991-92 CAPRICE, CAMARO AND CORVETTE 1991-92 C/K, RN, S/T, P TRUCKS AND G, M/L VANS

TRANSMISSION APPLICATIONS: SUBJECT: 1991-92 HYDRA-MATIC 4L60 (MD8) New Fluid Level Indicators and 1991-92 HYDRA-MATIC 4L80-E (MT1) Fluid Check Procedures

TRANSMISSION MODELS: VEHICLE APPLICATIONS: All B, F, Y - Cars C/K, RN, S/T, P - Trucks G, M/L - Vans

New Fluid Level Indicators:

During the 1991 and 1992 Model Years, changes were made to the fluid level indicators (dipsticks) in most HYDRA-MATIC 4L60 and all HYDRA-MATIC 4L80-E transmissions.

The new fluid level indicators (all except 91 S/T trucks, G and M/L vans with 4L60) have a cold fill area that is located lower on the stick than the previous fluid level indicators. The area was moved in response to a fluid level study which showed the previous markings did not reflect current hot fluid expansion rates.

The cold area on the fluid level indicator may still have two holes (dimples) to mark it, or may now be a solid area that says "COLD". See figure 1 to identify which indicators have dimples to mark the cold area and which have been changed to say "COLD".

When dealer prep personnel check transmission fluid levels in these vehicles, it is important to know the temperature of the transmission fluid before determining that fluid needs to be added. The dipstick "hot" and "cold" markings are calibrated to correspond to the following temperatures:

HOT 180-200 degrees F (82-94 degrees C) COLD 75-85 degrees F (24-29 degrees C)

This means that if the fluid level is in the "COLD" range area while the fluid temperature is 75-85 degrees F, the fluid will always expand to be within the "HOT" range area when the fluid temperature is 180-200 degrees F.

Fluid level may be checked and adjusted only if the fluid temperature falls within either the "HOT" or "COLD" range area.

Driving the vehicle a few miles will not expand the fluid into the hot (crosshatched) range. DO NOT ADD FLUID DURING A HOT CHECK UNLESS YOU CONFIRM FLUID TEMPERATURE IS 180-200 DEGREES F, AND THE INDICATOR STILL SHOWS THE FLUID IS BELOW THE CROSSHATCHED AREA.

DO NOT ADD FLUID DURING A COLD CHECK UNLESS YOU CONFIRM FLUID TEMPERATURE IS 75-85 DEGREES F, AND THE INDICATOR STILL SHOWS THE FLUID IS BELOW THE "COLD" AREA.

Since the cold area has been lowered on the fluid level indicator, if the transmission fluid is not warmed up enough, you will get a false low reading. With the previous fluid level indicator it was possible to have the transmission fluid in the crosshatched area after a short drive. It is unlikely that the new indicator will show fluid in the crosshatched area after a short drive with the transmission filled to the proper level.

New PDI Fluid Check Procedure:

NOTICE: Too much or too little fluid can damage the transmission. Too much can mean that some of the fluid could come out and fall on hot engine parts, starting a fire. Be sure to get an accurate reading when you check the transmission fluid.

Wait at least 30 minutes before checking the transmission if the vehicle has been driven:

- When outside temperatures are above 90 degrees F (32 degrees C).

- At high speed for quite a while.

- In heavy traffic-especially in hot weather.

- While pulling a trailer.

To check transmission fluid hot: A hot check is made when the transmission temperature is 180-200 degrees F (82-94 degrees C). This can be accomplished by driving about 15 miles (24 km) when outside temperatures are above 50 degrees F (10 degrees C). If it's colder than 50 degrees F (10 degrees C), you may have to drive longer.

To check transmission fluid cold: A cold check is made when the transmission temperature is 75-85 degrees F (24-29 degrees C). You may have to let the engine run at idle to warm the fluid, or let the vehicle sit with engine off to cool the fluid. Let the engine run at idle for five minutes if outside temperatures are above 50 degrees F (10 degrees C). If it's colder than 50 degrees F (10 degrees C), you may have to idle the engine longer.

Determining Fluid Temperature: There are several ways to determine fluid temperature.

You may attach a thermocouple to the dipstick and directly read fluid temperature.

If the transmission is a HYDRA-MATIC 4L80-E, you can hook up a Tech 1 or another scan tool and read the transmission sump temperature. (Most trucks that currently use the HYDRA-MATIC 4L60 will be able to read fluid temperature data with the Tech 1 during the 1993 Model Year. All current HYDRA-MATIC 4L60 vehicles will have this capability during the 1994 Model Year.)

If you know the ambient temperature is 75-85 degrees F (outdoors or indoors), let the vehicle sit several hours until the fluid temperature stabilizes.

If your dealership services both HYDRA-MATIC 4L80-E and 4L60 transmissions, you can take several cold readings on a 4L80-E, and assume that the 4L60 transmissions are at the same temperature. This obviously only holds true if the vehicles have been processed the same way (i.e. both sitting at same ambient temperature for same length of time, or both idled for same amount of time).

To check the fluid hot or cold:

- Park the vehicle on a level place.

- Place the shift level in "P" (Park) with the parking brake applied. With your foot on the brake pedal, move the shift lever through each gear range, pausing for about three seconds in each range. Then, position the shift lever in "P" (Park). Let the engine run at idle for 3-5 minutes.

Pull out the dipstick and wipe it with a clean rag or paper towel.

- Push it back in all the way, wait three seconds and then pull it back out again.

Check both sides of the dipstick and read the lower level. The fluid level must be in the cold area for a cold check or in to the hot (crosshatched) area for a hot check.

- If the fluid level is where it should be, push the dipstick back in all the way. If the dipstick has a locking top, flip the handle down to lock the dipstick in place.

To Add Transmission Fluid:

If the fluid level is low, add only enough DEXRON IIE to bring the fluid level in to the cold area for a cold check or the hot area for a hot check. It doesn't take much fluid, generally less than a pint. Don't overfill.

After adding fluid, recheck the fluid level.

When the correct fluid level is obtained, push the dipstick back in all the way. If the dipstick has a locking top, flip the handle down to lock the dipstick in place.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.