Why a Drain and Refill Does Not Change the Transmission Fluid

The Pan Holds Only Part of the Charge

A large share of the fluid sits in the torque converter and the cooler circuit, not in the pan. Draining removes what falls out under gravity, so a fresh fill is immediately diluted by the old fluid still in the system. The customer pays for a fluid service and gets a partial one, which is why the original harsh-shift or slipping complaint often returns.

What Equivalent Exchange Means

An exchanger pushes new fluid in while the old fluid comes out, measuring both so the quantities match. The ATF500 performs a high-precision equivalent exchange under fully automatic electronic control, and the ATF-7800 states an equal exchange error of ±0.01 L.

Getting the Flow Direction Right

Connect the cooler lines the wrong way round and contaminated fluid is pushed back into the gearbox. The ATF500, ATF500S and ATF-7800 all identify the oil inlet and outlet direction automatically and switch the flow accordingly, which removes the most damaging mistake in the procedure.

Clean Before You Fill

Automatic cycle cleaning runs the system through before the new fluid goes in. On the ATF-7800 the fluid is also filtered to 5 μm, which keeps debris out of the charge you have just paid for.

• Automatic transmission cycle cleaning on the ATF500 and ATF500S
• 5 μm oil filter accuracy on the ATF-7800
• Twin 20 L tanks on the ATF-7800 keep new and used fluid separate

Quantity and Temperature Are Model Specific

Many transmissions specify a level check at a defined fluid temperature and an exact fill quantity. The ATF500S and ATF-7800 carry a database of standard oil quantity by model and display both new and old fluid temperature, and both can reduce the transmission oil quantity automatically where the procedure calls for it.

Which Machine to Choose

All three do the exchange. The difference is how much guidance the technician gets.

• ATF500: automatic exchange with an LCD display and connectors for European, American and Asian systems
• ATF500S: adds a large touch screen, the model database, automatic filling and optional new oil heating
• ATF-7800: 10 inch touch screen, stated ±0.01 L exchange accuracy, 5 μm filtration and twin 20 L tanks