2003 GMC Sonoma Owner's Manual - Page 287

How to Add Fluid Refer to the Maintenance Schedule to determine what kind of transmission fluid to use. See Part D: Recommended Fluids and Lubricants page 6-32. on Add fluid only after checking the transmission fluid while it is hot. (A cold check is used only as a reference.) If the fluid level is low, add only enough of the proper fluid to bring the level up to the HOT area for a hot check. It doesn't take much fluid, generally less than one pint (0.5 L). Don't overfill. 3. Check both sides of the dipstick, and read the lower level. The fluid level must be in the COLD area, below the cross-hatched area, for a cold check or in the HOT area or cross-hatched area for a hot check. 4. If the fluid level is in the acceptable range, push the dipstick back in all the way; then flip the handle down to lock the dipstick in place. Notice: We recommend you use only fluid labeled DEXRON@111, because fluid with that label is made especially for your automatic transmission. Damage caused by fluid other than DEXRON@ 111 is not covered by your new vehicle warranty. After adding fluid, recheck the fluid level as described under "How to Check earlier. When the correct fluid level is obtained, push the dipstick back in all the way; then flip the handle down to lock the dipstick in place. 5-24