"How long should an automatic Transmission last?"

Obviously, this is a general question, but I have a general answer to go with it. Most late model transmissions are designed to last 80,000 miles. This is not to say that all fail at 80k, but the transmissions I see normally begin to fail at about 70k or 80k. Some may last longer, and some may not even last that long. The only reason that I bring this up, is that many people have transmissions that have 80 or 100k miles on them, and the transmission is beginning to give them problems. They frequently write me, and ask what they can do to prolong the life of their transmission, fixing the problem at present, and squeezing a little more mileage out the transmission, rather than overhauling the transmission. Automatic transmissions are very complicated, and very fussy about debris. When a part, within the transmission, fails, it, often times, showers debris throughout the transmission. For this reason, most transmission failures require a complete overhaul to clean the transmission thoroughly, eliminating all traces of the debris generated by the failure. In addition, the debris tends to cause other problems, with sticking valves within the valve body, and governor, and with tight tolerance parts, such as the pump, which are often damaged by the debris. In addition, diagnosing the exact cause of a transmission problem is very time-consuming, often requiring disassembly, and upset of many vulnerable components and the reassembly of used components that are not cleaned, and inspected thoroughly. This can lead to new problems when the transmission is put to use again. It can be very unwise to spend 10 hours diagnosing, and repairing a transmission, with high mileage, instead of overhauling the transmission completely, taking care of all potential, as well as existing, problems.