Okay so a few days ago while driving home from work, I notice an oscillating noise at exactly 38mph and 48 mph. I haven't tested other speeds but the noise is only present at those exact speeds.

The sound it makes is kind of a faint oscillating hum that sounds like wum-wum-wum-wum and it only happens under acceleration and goes away right when I take my foot off the pedal.

I can hear it from somewhere behind me mostly driver side though. 2002 with 86k miles and has 4.77 from puddymod(dunno if this might cause that kind of noise)

Any help would be appreciated!

 

If it only happens at certain speeds you are hitting a resonance frequency (Google "harmony resonance"). I would check tire balance first....you may have thrown a tire weight. Also check tire pressures first.

Utah