Well, I guess you can feel stupid if you want to, but allow me to add another dimension to the story. I have an 1988 Grand Caravan that I used to drag around a tandem axle enclosed trailer that's bigger and heavier than the van for fifteen years. It got the transmission fluid changed once at 85,000 miles because the side cover rusted out. Figured I would change the fluid and filter while I was at it. The van rusted away with 281,000 miles last year and the fluid and filter had never been replaced again. That is not neglect. That is abuse, but there was never a problem with the transmission.
Obviously I am not recommending anyone else do that, but it shows what some vehicles are capable of. The next person might not have such good luck. Unless it is spelled out differently in your owner's manual, the industry standard used to be to change the fluid and filter every three years or 36,000 miles. It should also be changed right after the transmission has been overheated, as in excessive tire spinning from trying to get unstuck, or when pulling a big load for a long distance. Overheated transmission fluid will be dark red, black, and / or smell burned. The fluid will still do its job, but there are additives in it that wear out and that get destroyed by overheating. Losing those additives can result in problems from foaming, loss of lubrication to critical parts, and abrasive wear to fiber parts and rubber seals.
Since the additives in transmission fluid last much longer than those in engine oil, there is a lower chance of damage occurring due to neglect, so do not beat yourself up too much.
Some mechanics will push for a transmission flush which is much more expensive. The jury is still out on the value of that, and I am not convinced yet. A simple fluid and filter change was all we ever did for decades. That gets about half of the old fluid out, and there were enough additives in the four or five quarts of new fluid to keep the transmission happy. With the newer computer-controlled transmissions, and the fact the engineers find all kinds of ways to cut corners, some people believe a flush is better because it gets one hundred percent of the fluid replaced, but a lot of mechanics do not do the additional step of removing the pan, (and the new fluid), to replace the filter. I consider the filter to be just as important as the new fluid.
Many people will tell you they had a catastrophic transmission failure shortly after having it flushed, but I suspect they had the flush done in an attempt to solve a problem that was already destined to cause that failure. That is just my opinion, but it seems to hold true more so for older or high-mileage vehicles. Some mechanics feel the force of the incoming fluid during a flush can dislodge debris that can tear or cut rubber seals, and that can cause a failure later. My recommendation is to have the fluid and filter replaced at one of your next oil changes. It is not unusual for your mechanic to find a little pile of debris in the bottom of the pan. If you aren't having any shifting problems now, that debris is not a cause to warn you of an impending failure or need for a transmission rebuild. Decline any such recommendation. That debris is in the pan because it was stopped by the filter from getting into the valves and passages. It came from flaking off some of the fiber clutch plates and "thrust washers". It is when there are large chunks of something in the pan that you need to worry, but you would have had some type of problem before that.
Tuesday, October 4th, 2016 AT 9:30 PM