Has anyone changed the fluid in the past and perhaps not used the Toyota WS transmission fluid called for. I haven't seen these transmissions give any trouble especially at such low mileage. Toyota say this fluid will go 100k but I would change it at 30 or 40,000 miles if it were my truck. Have the trans oil pan removed to get all the oil out and inspect for debris in the oil pan. Toyota do not approve of any other fluid or additives. Generally I don't aprove of a lot of additives that make wonderful claims but a company called Lubegaurd make a ready available additive that works great for other transmissions but I have never had to use it with WS fluid and would call and talk to a Lubegaurd engineer before putting in your transmission. Toyota will not approve!