The way we checked for moisture in transmission fluid when I was starting out was to put some in a metal spoon and hold a lighter under it while looking for boiling or spitting. They have since began using test strips made specifically for this test.
FLUID MOISTURE TEST STRIPS FOR 5 OILS # 80600
Detects 0 - 5% Moisture Content In:
Engine (Gas & Diesel) Oil, ATF, Power Steering, Hydraulic & ALL Brake Fluids DOT 3, 4, 5.1, Synthetics & Conventional.
Water reduces the fluid's ability to do its work and promotes corrosion. In the case of the Brake Fluids, water reduces the boil point of the fluid potentially causing a safety hazard event. Fluid Diagnostic Test Strips assess the health of the fluid and identify when a fluid needs to be changes. Determining the presence of water is important to maintain the integrity of the vehicle components and early detection of moisture will minimize the impact of corrosion - avoiding costly repairs and loss. Water breaks down oil-additive packages. It promotes the formation of acids that corrode metal surfaces, supports oxidation in mineral-based oils, supports biological or microbial growth, especially with prolonged idling.
Test strip must be used immediately after opening foil pouch.
# 80600 Replaces ACUSTRIP #'s 6000, ACU6000, 40002
Moisture is a death sentence for automatic transmissions. If not immediate failure it will shorten the life span significantly.
Brad