Transmission Fluid Service at Johnny's Automotive

Transmission fluid holds down three jobs at once, which is more than any other fluid in your vehicle. In an automatic it's the hydraulic fluid that applies the clutches and makes a shift happen, it lubricates gears and bearings, and it carries heat out to the cooler. When it degrades, all three of those get worse together, which is why worn fluid can feel exactly like a mechanical problem.

Heat is what uses it up. Towing a trailer, hauling a load, and long stretches of stop and go traffic in August all push fluid temperature up, and heat is what breaks down the additives that make the fluid work. Two identical trucks can be a hundred thousand miles apart in fluid condition based on nothing but how they spent their lives. So we go by the condition of the fluid and by what your manufacturer schedules for your specific transmission, not by one number applied to everything in the parking lot.

That brings up drain and fill versus flush. A drain and fill replaces what comes out on its own, which leaves some old fluid in the system. A flush exchanges considerably more of it. Which one fits depends on your transmission and what the manufacturer specifies, and there's a third case worth saying out loud: on a very high mileage transmission that has gone a long time without service, changing everything at once is not automatically the safe choice. That's a judgment call we make with you, after looking at the fluid and at how the vehicle is behaving, rather than a rule we apply to every older truck that comes through the door.

The fluid spec is not a small detail. Many transmissions require one particular fluid, and the wrong one can cause shudder, poor shift quality, or damage. The same goes for the filter on transmissions that have a serviceable one. We use what your vehicle calls for, and we'll tell you exactly what went in it.