I have a 2006 Prius that has 102k miles that is beginning to make a lot of screeching-grinding noise under the hood. This is true between the speeds of 45 and 60 miles per hour. If I go over 65 miles per hour, the noise disappears. If I go under 40 miles per hour, the noise is not present. If I accelerate or go uphill, the noise diminishes. If I decelerate or go downhill, the noise increases. It makes no difference if I sway back and forth on the road, so it is not a wheel bearing issue. I believe it is the bearings in the transaxle and the fluid needs to be changed. The fluid has not been changed in 60k miles since I purchased it. When I take the car to the Oxnard Toyota Dealership in California, they (two Prius Techs) say that the fluid in the transaxle is sealed for the life of the car and never needs to be changed. They say that the transaxle is made of a bunch of magnets and there is very little fluid in there so lack of fluid is not an issue or the problem. They observed no cracks in the transaxle housing and believe the fluid level to be fine. They refuse to check or replace the fluid. They told me that they want the problem to get worse so they can diagnose it. They hear the noise as a "harmonic" noise and think it is electrical in nature. They erased all the old codes on the car and want me to bring the car back to them so they can view the new codes. I had Luscious Garage in San Francisco change the Transaxle Fluid. John there said that there was no excessive metal shavings, etc, on the magnetic plug. It did not completely solve the noise problem, but the car is making much less noise than before the fluid change. There is a noticable change. Can I use Lucas Transmission Fix or some other transmission additive in the transaxle as an attempt to reduce the noise further?
Additives to reduce "noise" will not fix the issue. I suggest you seek further advise from the folks at Luscious based on their reputation, experience and proximity.
The fluid Toyota uses for transaxle lubrication and cooling is specially formulated not to ruin the windings of the electric motors in the transaxle. I wouldn't use anything not recommended boy Toyota. I also support frodoz737's suggestion re Luscious.
Third that. Those guys in Oxnard have blown their credibility. Ask Luscious specifically about the noise and see what they diagnose.
+1 I'll second going to a competent shop. It's unlikely the screeching is actually coming from the transmission. If it were there would be metal in the oil and it would be rapidly getting worse. I suspect the reduction in noise with the fluid change was either a coincidence or placebo effect. Rhino, please don't take the placebo comment as demeaning, engineers and mechanics get placeboed too.
I had the same problem and i thought it was transmission problem and changes Transmission fluid, We only got 2 litres of fluid out of transmission instead of 3.3 litres. But after new Toyota WS fluid the problem persists. Solution: I used Hi Octane fuel and this noise disappers. Please try 92 or 95 octane fuel.
Don't use anything in you transmission. You could damage the electric motor/generators. Sorry! Didn't realise I had already replied.
