When a flush might help:
* Old, dirty fluid: If the shifting issues are due to old, contaminated transmission fluid (which is common with age), a flush and fill with fresh fluid can improve performance. The old fluid can contain sludge, debris, and varnish that impede proper valve operation and lubrication.
When a flush might NOT help (or even hurt):
* Internal mechanical problems: If the shifting problems stem from worn-out clutches, bands, seals, or other internal components, a flush won't fix the underlying mechanical issues. In fact, flushing could dislodge debris that's been keeping things barely functioning, leading to complete transmission failure.
* Incorrect fluid level: Low or overfilled fluid can cause shifting problems. A flush doesn't address this. A proper level check is crucial.
* Electrical issues: Problems with solenoids, sensors, or the transmission control module (TCM) won't be fixed by a fluid change.
* Valve body problems: A faulty valve body can cause poor shifting and a flush won't address this internal component failure.
In short: A transmission flush is a relatively inexpensive and simple procedure, but it's more of a preventative measure or a potential fix for minor shifting issues related to dirty fluid. If the shifting problems are severe or have other accompanying symptoms (like slipping, noises, or leaks), you should have a professional mechanic diagnose the problem before attempting a flush. A misdiagnosis and a flush could lead to costly repairs. A professional inspection can determine the cause of your shifting issues and whether or not a flush would be beneficial.
