1994 GMC Sonoma Owner's Manual - Page 236

4. If the fluid level is in the acceptable range, push the dipstick back in all the way; then flipthe handle down to lock the dipstick in place. How to Add Fluid Refer to the Maintenance Schedule to determine what kind of transmission fluid to use. See "Recommended Fluids and Lubricants" in the Index. If the fluid level is low, add only enough of the proper fluid to bring the level up to the COLD area for acold check or the HOT area for ahot check. It doesn't take much fluid, generally less than a pint. Don't overfill. We recommend you use only fluid labeled DEXRON@-111 or DEXRON@-IIE, because fluids with that label are made especially for your automatic transmission. Damage caused by fluid other than DEXRON@-I11 or DEXRON@-IIE is not covered by your new vehicle warranty. After adding fluid, recheck the fluid level as described under "HQWto Check." 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. Manual Transmission Fluid When to Check A good time to have it checked is when the engine oil is changed. However, the fluid in your manual transmission doesn't require changing. How to Check Because this operation can be a little difficult, you may choose to have this done at a GM dealership ServiceDepartment. If you do it yourself, be sure to follow all the instructions here, or you could get a false reading.