They are referring to a transmission flush. You are talking about a simple fluid and filter change, which is what I recommend. Changing the fluid and filter simply restores the worn-out additives and removes much of the varnish that has formed from the fluid being hot. Only about half of the old fluid drains out and needs to be replaced. The flush gets pretty aggressive and replaces one hundred percent of the fluid. A strong detergent is added first, then must be removed as part of the flush. Some of us feel that detergent can dissolve some of the friction material on the fiber clutch plates.
My limited experience from talking with people who have had flushes done is they were usually trying to solve a pre-existing problem, and when the flush didn't solve it, and that problem became worse, they blamed the flush for the transmission's failure. In fact, the failure was likely going to happen anyway. My opinion is if there is no problem now, there is no value in having a flush service performed, and if there is a problem, a flush is not likely to solve it. If there is any slippage problem, that's due to wear of the clutch plates or a cracked or torn rubber lip seal in the clutch pack. Those are mechanical problems and a flush will never fix a mechanical problem. If the fluid and filter change is way overdue, varnish build-up in the valve body can prevent some of the shift valves from sliding smoothly and freely. That can result in delayed or late shifts. A flush, with that harsh detergent, may solve that, but given some time, the severity of that problem is likely to be reduced just from the new additives from a fluid and filter change.
Tuesday, January 2nd, 2018 AT 6:01 PM