My roomate's transmission was leaking fluid, and I finally convinced him to change out the fluid and filter which would also replace the bad pan gasket that was causing the leak. After he did so, his car refused to move at all. Not knowing what he did to the car I was unable to give any advice, so he had it towed to a transmission shop to take a look at the problem. They ended up replacing the entire transmission and told that the problem was due to his neglect of the leak over time. Over the years by several people, I have been told that the electronic automatic transmissions get to a point where servicing them is actually detrimental to their operation. For some reason, the trannies go into a failsafe mode and afterwards any work done has no effect on them if it doesn't make the situation worsen. I know several shops in San Antonio that will actually ask when scheduling transmission work how many miles are on the vehicle and how long it has been since the transmission has last been serviced. Some will tell you right over the phone if either mileage is too high that the transmission runs the risk of needing rebuilt, and the garages who only specialize in fluid/filter changes won't even touch the vehicle and will say to take it to a transmission shop. I was even told this by shops who know I do my own transmission work. They advised that I change my fluid out regularly to prevent having to bring it in to get the transmission replaced.
My point is: If the transmission is still leaking, have it taken care of. If you think this shop is trying to pull one on you, get a second opinion. Do NOT wait for this leak to get any worse. IF these various mechanics I spoke with are correct, you will not want to prolong the situation. Better to repair the leak now than to wait for when the car will not move anymore. I have not seen proof of and have no way of proving whether or not these transmissions behave in the manner described, but I figure that it is a good precautionary measure to take.
