Here at Wayne’s Automotive Center, Reno drivers often ask us: “What’s the difference between a pan drop and a transmission flush?” Let’s start with what they have in common; both are performed to replace old transmission fluid with new fluid. They differ in how they accomplish this task.
A pan drop removes the pan on the bottom of the transmission and drains the fluid out using gravity. Any debris which has collected in the pan can be removed and the filter can be replaced, provided the transmission has one. The debris in your vehicle’s transmission pan can give your technician a good idea of what is going on inside your transmission. Your technician can then advise you on any preventative maintenance which needs to be performed.
Dropping the pan does end up leaving about half the old fluid remaining in the torque converter. Less than idea because additives from the new fluid will be used up by the contaminants in the old fluid rather than by the transmission itself. To get around this issue a mechanic should drain and replace the fluid multiple times to dilute it to a satisfactory condition. Your vehicle’s transmission may not have a pan to drop, the equivalent for such transmissions is a drain and fill. A plug is removed and the fluid drained by gravity. New fluid is added after the old fluid stops draining out. The cycle is repeated until the fluid is diluted properly just like a pan drop.
Flushing the transmission uses a machine to pump the old fluid out while pumping new fluid in. This method allows for the replacement of all fluid in the transmission in one go. On its own, a transmission flush is much faster and more thoroughly replaces fluid than a pan drop. Ideally, pressure from only the vehicle’s own pump is used to circulate the fluid. Some machines apply additional pressure to accelerate a transmission flush or flush cleaning fluid through the transmission. Neither of these is healthy for the transmission, potentially damaging seals and/or lodging sludge and debris in places it shouldn’t be.
A full transmission flush should include a pan drop and inspection of the oil for any signs or precursors of issues. The condition of the old fluid, contents of the pan, and what is trapped in the filter will tell your technician a great deal about your transmission’s
condition. If the filter isn’t replaced it can become clogged during a flush, starving the transmission pump of fluid. No fluid for the pump to circulate means components go unlubricated. Unlubricated components heat up, wear, slip, and eventually fail.
Of course, the goal of all of this is still replacing the transmission fluid. Whether you’re having a transmission flush or a pan drop it is important to use the right fluid. OEM specified fluid from a quality brand is always the best. Even if it means you need to purchase the fluid from your dealership.
The friendly service pros at Wayne’s Automotive Center recommend following your vehicle’s owner’s manual recommendations for servicing your transmission. Your transmission is just as important for getting you around Reno as your engine is, don’t neglect it.