I don't plan on installing a thermostat. I just don't think it is necessary as the temp of the trans fluid has no bearing on performance as far I as know...Anyway....
I have a question for you. How did you determine the fluid level after the install? Did you follow the factory service manual way (which is a total pain) or use some other method?
Ok, I just did a partial replacement of transmission fluid. After doing more thinking, I went with Amsoil Fuel Saving Signature series synthetic fluid.
It was a relatively simple procedure. This vehicle has both drain fitting and a level fitting on the bottom of the oil pan, unlike some front wheel drive Toyotas with only one fitting.
Factory procedure is a bit complicated and requires a special tool that applies vacuum to the fill hole. They also use a special, variable length tube to determine proper fluid level. This tool is not absolutely required if you have time to allow your transmission to cool down. The tool can be very useful to save a lot of time so they can measure proper fluid level at any temperature. The existing factory level tube will measure correct level only within a narrow temperature range specified by the manufacturer. Any excess fluid will simply drain out.
All you need is a way to measure fluid temperature in the pan and a way to fill transmission with fresh transmission fluid. I bought a Scangauge II and a manual pump from Amsoil.com that fits Amsoil oil bottles. A similar pump can be purchased on Amazon for around $10 if you plan to use Toyota WS fluid. Scangauge can be programmed to read transmission fluid temperature.
All you need is to let the engine and transmission to cool below 90 degrees. Let it sit overnight for best results. Buy a set of new drain plug gaskets from Toyota. I reused the old ones with no issues.
Vehicle must be level. Make sure you can remove the fill plug before draining any fluid out. Loosen the level check plug (front) a bit but don't remove it yet
If you want to check the level only, start the engine and shift from park to reverse - drive and back to reverse. Leave at each position for a few seconds to allow the fluid to circulate. Keep the engine running in park. Once transmission temperature gets over 90 degrees, unscrew the level check plug and watch for any fluid to come out. Nothing or very little should come out until temperature gets to around 104 degrees. Once you see fluid start dripping at around 104 degrees, put the plug back in place, stop the engine and torque the plug to spec.
If no fluid came out at 110-115 degrees, you need to add some fluid. Reinstall the level check plug but don't make it too tight as it will be removed again. Stop the engine and let it cool to bring transmission temperature below 90 degrees. You will probably need to raise the vehicle to reach the fill plug. Open the fill plug and add about half a quart of fresh fluid. Reinstall the fill plug. Don't add more than a quart. Start the engine, run through gears and back to park, keep the engine running, remove the level check plug once the trans temperature gets above 90 degrees. Be careful not to burn your hands around the exhaust piping. Some fluid will come out. Let it drip until transmission temperature gets to 104 degrees. Once at 104 deg., reinstall the level drain plug, with a new gasket, and torque slightly. Stop the engine and tighten the plug to spec. That's it.
To drain and replace ATF fluid, you will first need to raise the vehicle so you can reach the fill plug on the transmission easier. Open the drain plug (rear) and drain the fluid. Measure the amount of fluid that came out. Reinstall the drain plug and tighten to spec. Use a new gasket if needed. Fill the transmission with the same amount of fresh fluid plus an additional 1/2 to 3/4 of a quart. Reinstall the fill plug and follow the same procedure as described above. It's very simple. The level check tube located above the level check plug will not allow you to overfill the transmission.
Some guys use an infrared thermometer to measure temperature of the transmission oil pan. Do this at very close range to get better results. Hope this helps.
Obviously, do this at your own risk. Take it to a dealer if you are not comfortable doing this yourself.
