2006 wrote:This post is a few .on the old, but I've been researching transmission fluid changes versus flushing. I'm waiting for a co-workers Vibe to become available and a transmission service is on the list when it is finally in my possession. I was leaning towards a flush after doing a filter/fluid change, but I stopped by the shop that built a 700R4 for my classic car. He told me that he has seen too many people come in after they had flushes performed on their vehicles. First one of the solenoids would be replaced, and after a while longer another would need replacement. Eventually he pulled these trannies for a rebuild. His theory is metal particles get stuck in solenoids (electromagnets) and foul them up. He advised against flushes for that reason. He told me....flush the crap outta that 700R4 of your or any other tranny prior to about 1991, but don't go flushing anything newer than that.
For that reason, I have decided to only do a filter/fluid change. But I will do another fluid change or two after a short time..... I would probably just suck the fluid out through the dipstick tube rather than drop the pan if it werent for the drain plug.
Sorry for the long post.
I talked to several transmission shops and they all said the same thing. If you keep up with the maintenance and flush it every 50-60k, then it's okay to do a flush. But if it's a used car, or you've gone a while without changing it, do not flush it, because you will end up flushing the crud and it will get into other parts of the transmission. Better to just drain, replace filter, then do it again in a year or another 30k miles. I'm on my second drain and fill and plan to do it again before winter, hopefully.
I have heard of ways of "flushing" it where you hook a hose to the trans line and then into a container and allow the trans pump itself to push the old fluid out, but that requires someone standing there constantly pouring new fluid into the transmission and may be too risky to do.