Hi,
I have a 1998 SC300, 104,000 miles, automatic. At 4000 RPM a vibration and or vibrating noise starts then increases in intensity to around 4800 rpm. It then completely goes away. I first noticed it when I dropped into passing gear on the highway, but I can duplicate the vibration/noise by just running the car in 1st or second gear up to the rpm range. The dealer just put a timing belt service in and replaced the VVTI that was also leaking. They can't seem to figure this out
after several days. Mounts have been checks and cat convertors are new.
Thanks for any help.