Auto Parts: Toyota Sienna transmission, toyota sienna, filter change

Question
My wife has a 2001 Sienna van. Recently, she noticed that it will "clunk" and jump into gear when she is taking off. Happens in either Drive or Reverse and seems worse when the car is cold. At one point, it would not go into R at all and, even though the shift lever moved freely, it seemed like it was locked up so it would not go into Neutral so we could push it. We put it in Drive and drove just a few inches (wall in front of us) and then we were able to go into Reverse like something was binding that was loosened up. Has 130K miles and sad to say never had a fluid or filter change. I'm going to change them to see if it helps and see if any metal filings in the pan. Any thoughts on what might cause this and how serious it might be? Thanks!

Answer
Ronnie,

At this point, your cheapest route to take is to go down and have the transmission fully flushed and filled.  With fresh fluid and filter, THEN you can get a better assessment of what's wrong with your vehicle.  If your fluid is low enough, it CAN cause the problems you are describing.  

For now, just get the fluid and filter changed out and see what happens.