Automatic Transmission Fluid

The car does not actually have an automatic transmission. It has a Power Splitting Device (PSD) which serves as a transmission, and it does use automatic transmission fluid. There is no dip stick as with a normal automatic. The PSD has a fill plug and a drain plug, if the oil is up to the fill plug it is OK. They should check it when you have your car serviced. I think it's only checked every 30K miles or maybe it's every 60K, Toyota did not expect any problems with it. Some of the experienced people on here recommend changing it (the fluid) at 30K, I will take their advice.

 

The PSD system is more like a manual gearbox in that the fluid in the case is not under pressure and is not used for any hydraulic purpose, other than common lubrication. There are a couple of oil drippers in the PSD case where fluid is pumped up from the sump into a dripper reservior so the fluid can flow downwards over moving parts from a high point in the case, assumably where splash lubrication would not be possible.

Although Toyota does not have a fluid change interval at 30k, I do not see how doing a fluid change would be dammaging. The only risk is getting a grease monkey in the Toyota garage doing it and missing a step or doing procedures which do not apply to the Prius. I think it is riskier to have extra services done to the vehicle than to stick with the schedule. Most tranny fluid service in most garages are done by grease monkeys who are trained to do certain steps to get the job done. A transmission specialist is not the one doing a fluid change.

 

This topic has some very good information including the location of the fill and drain plugs:

http://priuschat.com/index.php?showtopic=18782&hl=PSD

Check posts number 29, 76, and 94 for example, there are pictures. There is also a caution not to remove the inverter coolant plug by mistake.