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Q: Noise during Acceleration. Starts at 5200 RPMs, 150,000 miles on 2000 Lexus RX300

For the past two years this Lexus has a hard to describe loud noise, like a high speed scraping, well you reach 5200 RPMs. To reproduce the noise, all you do from a stop is floor it and when it reaches 5200 the noise happens. Then the trans shifts and the RPMs drop to 4600 and the noise is still there, but slightly less. It isn't speed dependent and A/C or alternator load doesn't matter. I just changed the timing and standard belts and pulleys. I was going to try it with the A/C and Alternator belt removed. Then if I can drive it with the P/S belt removed. I replaced the exhaust front pipe and welded all holes in the exhaust behind the rear cat. In the two years the noise hasn't gotten any worse or less.
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very high rpm for a motor with that many miles. why do you rev it that high??
could be bearings in the motor or oil pressure. My suggestion is to take care of it by lowering your rpm to normal values or you may do major engine damage.

The transmission normally shifts at 6000. It doesn't sound like a bad bearing. It might be the A/C clutch. I'm not sure why it hasn't gotten worse in 2 years. Once the noise starts at 5200 it continues at the same level all the way to 6000, and continues down to 4600. If I let up on the throttle, and the RPMs drop, it goes away.
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