GM S10/S15/Sonoma Pick-Ups 1982-1993 Repair Guide

Automatic Transmission

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FLUID RECOMMENDATIONS



When adding fluid or refilling the transmission, always use Dexron II® automatic transmission fluid or the latest superceding Dexron® fluid.

LEVEL CHECK



See Figure 1

Check the automatic transmission fluid level at least every 7500 miles. The dipstick can be found in the rear of the engine compartment. The fluid level should be checked only when the transmission is hot (normal operating temperature). The transmission is considered hot after about 15-20 miles of highway driving.

Although the transmission should be checked while the fluid is at normal operating temperature, do not check it if it is at the extreme high end of the operating temperature range. Wait at least 30 minutes if you have just be driving the vehicle in ambient temperatures in excess of 90°F (32°C), at highway speeds for a long time, in heavy traffic (especially in hot weather) or have been pulling a trailer.



Click image to see an enlarged view

Fig. Fig. 1: Automatic transmission dipstick marks; the proper level for a hot transmission is within the shaded area

  1. Park the truck on a level surface with the engine idling, then shift the transmission into Park and firmly set the parking brake.
  2.  
  3. With your foot on the brake pedal, move the selector through each gear range (pausing for about 3 seconds in each gear), then place it in Park. Allow the engine to run at idle about 3 more minutes.
  4.  

When moving the selector through each range, DO NOT race the engine.

  1. With the engine running at a low idle, remove the dipstick, wipe it clean and then reinsert it firmly. Be sure that it has been pushed all the way in, then pause 3 seconds. Remove the dipstick again and check the fluid level while holding it horizontally. The fluid level should be between the upper notch and the FULL HOT line. If the fluid must be checked when it is cool, the level should be between the lower 2 notches.
  2.  

Most of the transmissions for the 4.3L engine are equipped with a flip-top handle on the dipstick. To withdraw these, flip the handle upward, then pull the dipstick from the guide.

  1. If the fluid level is low add DEXRON II® automatic transmission fluid. The fluid must be added through the transmission dipstick tube, which is easily accomplished using a funnel. Add fluid gradually, checking the level often as you are filling the transmission. Be extremely careful not to overfill the transmission, as this will cause slippage, seal damage and overheating. Approximately one pint of ATF will raise the fluid level from one notch/line to the other.
  2.  

Always use DEXRON II® or the latest superceding Dexron® ATF. The use of ATF Type F or any other fluid will cause severe damage to the transmission.

The fluid on the dipstick should always be a bright red color. If it is discolored (brown or black), or smells burnt, serious transmission troubles, probably due to overheating, should be suspected. The transmission should be inspected by a qualified technician to locate the cause of the burnt fluid.

DRAIN AND REFILL



See Figure 2

The truck should be driven 15-20 miles to warm the transmission fluid before the pan is removed.

The fluid should be drained while the transmission is warm.

  1. Raise and support the front of vehicle safely using jackstands.
  2.  
  3. Place a drain pan or under the transmission housing a fluid pan.
  4.  
  5. Remove the pan bolts from the front and the sides, then loosen the rear bolts 4 turns.
  6.  

On some vehicles, it may be necessary to support the transmission tailshaft and remove the crossmember just behind the transmission for pan clearance or access to the pan bolts.

  1. Using a small prybar, carefully pry the pan downward at the front of the transmission. This will allow the pan to partially drain. Remove the remaining pan bolts and lower the pan from the transmission.
  2.  

If the transmission fluid is dark or has a burnt smell, transmission damage is indicated. Have the transmission checked professionally.

  1. Empty the transmission pan of the remaining fluid, then remove the gasket material and clean with a solvent.
  2.  
  3. Using a putty knife, carefully clean the gasket mounting surfaces.
  4.  

To install:
  1. Use a new gasket and sealant and install the transmission pan. Install and tighten the retaining bolts to 8 ft. lbs. (11 Nm) using a criss-cross pattern.
  2.  



Click image to see an enlarged view

Fig. Fig. 2: Fluid may be easily added through the automatic transmission dipstick guide using a funnel with a flexible hose

  1. Remove the jackstands and carefully lower the vehicle.
  2.  
  3. Immediately refill the transmission housing using Dexron II® automatic transmission fluid. Add the fluid through the filler tube. Please refer to the capacities chart found later in this section to determine the proper amount of fluid to be added.
  4.  


CAUTION
DO NOT OVERFILL the transmission. Foaming of the fluid and subsequent transmission damage due to slippage can result.

  1. With the gearshift lever in PARK, start the engine and let it idle. DO NOT race the engine.
  2.  
  3. Apply the parking brake and move the gearshift lever through each position. Return the lever to Park and check the fluid level with the engine idling. The level should be between the two dimples on the dipstick, about 1 / 4 in. (6mm) below the ADD mark. Add fluid, if necessary.
  4.  
  5. Check the fluid level after the truck has been driven enough to thoroughly warm the transmission.
  6.  

PAN AND FILTER SERVICE



  1. Remove the transmission oil pan and drain the fluid. For details, please refer to the procedure located earlier in this section.
  2.  
  3. Remove the screen and the filter from the valve body. Most screens are retained using a bolt fastener, though some may use an interference fit between the screen tube and valve body.
  4.  

To install:
  1. Install a new filter using a new gasket or O-ring.
  2.  

If the transmission uses a filter equipped with a fully exposed screen, it may be cleaned and reused.

  1. Install the transmission oil pan and properly refill the transmission.
  2.  

 
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