HI,,i have noticed that if i put my 86 iroc in DRIVE,,I can hear a sound,,(hard to desribe exactly) but it most closely sounds like a vacuum. OR it sounds like air being sucked in. I dont notice this sound as much if i use OVERDRIVE. Only when its in DRIVE. Is this normal? i cant figure out what this sound is.thanks for any answers.. oh,,and the sound goes up and down with the RPMs,,once im moving about maybe 40mph and up.