1990 Buick Lesabre Acceleration Noise

acceleration
buick
lesabre
noises

#1

My 1990 Buick Lesabre Custom started making an “errrrr” (kinda sounds like someone is hitting a rubber hose really fast) noise a few months ago. It only happens in forward and in park when the gas pedal is pushed. It doesn’t make it going backward. Speed doesn’t affect the noise, but it has been loud enough to hear it over the stereo. Then some days it doesn’t make the sound at all or it happens early or late in my commute. Other days the car makes it the whole time. I’ve taken it to several mechanics and a transmission place. I had the mechanics sit in the car and hear the noise, but when they put it on the lift, they couldn’t replicate it. They told me they have no idea what it could be and to run it until it just makes the noise constantly and then take it back in. Is this something I should worry about, or is this just what happens to cars with over 125,000 miles?