2004 Prius leaking transaxle oil, just a little bit.

The rear brakes are adjusted on the US version of the Prius through a hole in the brake back plate. There is a star wheel inside the drum that can be flicked round with a flat screwdriver through this hole. The hole has a rubber bung in it to stop the ingress of dirt.The rear brakes seldom if ever need to be replaced on the Prius.

 

There is no gasket on the transmission end plate if that is where it is leaking from. I would try just tightening the bolts or at least retorque the to see if it helps.

If the amount is very small and not making a mess on the drive ect I would leave well alone and monitor the leak keeping a check on the fluid level.

One other point is that there is a one way breather valve fitted under the inverter in the transmission, "should let air out but not in" so that the transmission works in a partial vacuum. If this is stuck or full of dirt this may be your problem.

 

I suggest you provide a closeup photo of the leaking area as well as a zoomed-back photo to provide perspective.

The halfshaft seals are known to leak. Those can be changed fairly easily after draining the transaxle ATF and removing the halfshaft.

The transaxle case itself usually will not leak unless the transaxle has hit something (like road debris.)

If the transaxle actually has to be removed and opened, I would expect that to cost much more than $300. Considering how many miles your car has logged, it might be better to buy a used transaxle from a donor car with a substantially lower odometer reading, and have that installed instead.

The rear brakes can use periodic adjustment. It might cost $100 to replace the rear brake shoes.

 

If you are going to remove the rear drums to inspect the brake shoes, either pull out the two light blue relays in the fuse box under the hood, or disconnect the 12 volt battery. Disconnecting the 12 volt will loose some radio settings, fuel consumption readout, and drivers window park setting, but these can be reset easily. Failure to do this can cause many complications.