As transmissions become more high tech, it’s harder and harder to diagnose hydraulic circuit problems. The continued evolution of closely toleranced and balanced hydraulic circuits, combined with more sensitive sensors that can pick up on the slightest bit of slippage, can lead to a host of major problems. Circuit leaks are more and more common .Because today’s transmissions are so much more precise, diagnosing hydraulic circuit problems has to be, too. After the dismantle and re-assemble of the valve body, vacuum testing is carried out to help us judge the integrity of it.