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Have you had the transmission fluid serviced at proper intervals in the past??
Flushing the transmission is a good idea because it replaces 100% of the fluid. However, if you have not been replacing the fluid at the correct intervals, you can do more harm than good by flushing the system.
Yes - I bought it with 80K on it and changed the fluid at 90K and now am at 115K
The shop said that at the 90K the fluid looked good but sinceI did not know when it was changed last I had them do a drain and replace.
The Flush makes more sense to me
But on my Honda Odyssey they do not recommend it
The only problem with flushing the transmission is that friction material from inside the transmission builds on the inside of it. When you flush the transmission, the additives in the transmission fluid break down that buildup. If there is excessive buildup (i.e. fluid has not been regularly serviced) then it could break loose and cause internal transmission issues.
Honda only recommends drain and fill of transmission fluid, however I have flushed several Honda transmissions with absolutely no problems. I believe that Honda is afraid of putting any additional stress on the transmission, as well as the major transmission problems that Honda has had with the Odyssey. Several year models of the Odyssey had warranty extensions due to transmission issues.
So have I been regular enough at 25K since the last one and at 90K the mechanic did it because I insisted as the fluid was not dirty at all
As long as the fluid has been serviced at the proper intervals, flushing the transmission would be better. With a flush you are replacing 100% of the fluid. With a drain and fill you can only replace around 33-40% of the total capacity of the transmission.