Why a transmission flush is never money down the drain
Chicago’s infamous summertime sweltering heat is back. Add in gridlock caused by construction zones, rush hour and too many vehicles sharing a major metropolitan road system, and you have a recipe for transmission troubles.
When a transmission fails, it’s usually a four-figure affair to fix it. But you can fight back: flush.
New vs. old: The transmission fluid on the left is the color you want to see. The sample on the right has seen better days.
Automatic transmissions contain a maze of passages through which transmission fluid must pass to ensure smooth gear-shifting. Unfortunately, transmission fluid deteriorates over time, turning from its original bright red to gray, brown or even black as dirt and metal particles from wearing gears contaminate it. When this fluid isn’t flushed regularly or thoroughly, it’s unable to build up sufficient hydraulic pressure to properly shift gears.
It’s important to distinguish between a transmission service and a transmission flush. Typically, a simple service involves draining—not flushing—the system, which only replaces some of the fluid. This means new fluid will be mixed in with old, quite possibly contaminated, fluid. During a service, some disassembly is required—fluid-pan removal and filter cleaning or replacement—increasing the risk of human error.
A flush, on the other hand, doesn’t require disassembly and will replace all the transmission fluid. The filter won’t need replacement since the pressure used during flushing is sufficient to clean it.
A service typically only replaces a few quarts of trans fluid that’s found in the body of the transmission. However, the typical transmission holds roughly 12 quarts, much of which is found in the torque converter, plus lesser amounts in the trans cooler and cooler lines. Without a flush—which uses pressure to remove every drop of old fluid—the bulk of old fluid will remain inside your vehicle’s trans.
One of the biggest benefits a flush offers is that it can uncover latent transmission-system problems, including compromised seals and cracks, before they have a chance to turn into big-dollar repairs.
Spending $150–$300 on a flush can save the $1,500–$3,500 it will cost to rebuild or replace a transmission.
If you’re unsure how frequently your fluid should be flushed, check your maintenance schedule or contact Hong Kong Auto Service.