I changed the transmission fluid in my 2000 Sienna.
First I did a drain and fill. I measured the amount I drained and added that much new fluid back in.

Then, since my fluid was brown, I proceeded to flush the system. Following advice I read on the internet, I disconnected both of the transmission cooler lines at the bottom of the radiator. I turned on the engine to see which line pumped out the fluid.

Then I ran the engine until a quart came out. Then I added a quart of new fluid. I repeated that cycle until I went through the remainder of my 14 quarts of fluid (the Toyota dealer service department said a flush takes about 14 qts). A couple times I would shift it to drive, R, 2, 1, while it was pumping out fluid to ensure all passageways were pumped out. I always measured what was pumped out and added that amount of new fluid back in.

Now here are some mysteries to me:
1. After I got down to my last 4 remaining quarts, it really wasn't pumping out fluid anymore. Instead it would spit, and drip out. Why would that happen?

2. I drove the vehicle about 10 miles in city and highway driving. It shifted smoothly. I didn't notice any problems at all, in fact it might've been even better than before. But when I got home and checked the fluid level (while the engine was running and after shifting through all the gears), it didn't even look like there was any oil on the dipstick. Why would that be. For every bit of fluid that came out, I put the same amount of new fluid in.

Your trans may sense temperature to control the fluid that goes to the cooler. Maybe the new fluid was cool enough that it quit circulating to the cooler. New hot fluid is sometimes difficult to read on a dip stick. Figuer it out by looking some more and make sure the level is correct.

Your trans may sense temperature to control the fluid that goes to the cooler. Maybe the new fluid was cool enough that it quit circulating to the cooler. New hot fluid is sometimes difficult to read on a dip stick. Figuer it out by looking some more and make sure the level is correct.

I also suspected that there may be some thermostat or something that controls the flow to the cooler. I haven't had a chance to check it out.

I guess I'm not going to worry. It shifts fine and it should have the proper amount of fluid since I put in the same amount that came out.

Thanks for the reply.

- Clint