2004 Toyota Sienna Transmission Fluid Change

SCEJANG

MEMBER
2004 TOYOTA SIENNA

2004 Toyota Sienna

Several dealers are making different recommendations, and I don't know which one to follow. Would you help?

Some dealers are recommending that I do full automatic transmission fluid flush because it ensures 100% fluid will be exchanged. Some dealers are against this since high pressure can damage seals & gaskets.

Instead, they are recommending that I do transmission fluid drainage, and do this every 15,000 miles. But, the other dealers are against it since it will exchange only 20% of the fluid.

Some dealers are recommending that you need to do this only every 90,000 mile interval.

I couldn't find any recommendation in Toyota's Owner's Manual regarding transmission fluid. What do I do?

1 Reply

KHLOW2008

MECHANIC
41,814 POSTS

Hi scejang,

Thank you for the donation.

Trust Toyota to come up with nothing about service intervals and replacement procedures and you got it.

I checked through my online repair manuals and could not find details about the service interval and procedures.

What I have to offer is from other manufacturers and my personal experience.

Honda strongly advises against flushing transmissions as it can cause more harm than good. The resaon is as you have stated and the recommended procedure is to drain and refill.

A shorter replacement interval such as 15 k miles is what I would recommend.

Some manufacturers recommend disconnecting the return hose from the radiator and running the engine with transmission in Neutral to drain the fluid and stopping the engine once fluid stops flowing. This would drain out more than the 20 % of the fluid in the trans.

Care must be taken during this process to avoid starting the engine for too long.

If the fluid condition is bad, dropping the oil pan, (if applicable) would be the better option of draining the fluid. After dropping the oil pan, loosen the valve body bolts slightly, sufficient for fluids to drain out of valve body and clutches would enable 80 % of fluids to be replaced.