My mechanic told me the best way to check if the fluid is going bad is to smell it.Sometimes even red fluid can be burning and you think its still good , but if there is any trace of a burnt smell , then its time to change it.They do offer a full transmission flush , it takes about an hour , and costs about 150 , but it takes all the fluid from your tranny , except whats in the torque converter , then they flush it out twice , then refill it.I did it once on my work van , but unfortunately I still had the tranny die at 375,000.

Ask around with local mechanics and see if they offer the full flush , and not the one where they just drain alittle and stick new stuff in. <img src="/forums/images/graemlins/kewl.gif" alt="" />