Whining noise in drive and reverse

I was driving my van for a long trip when all of a sudden, while I was taking the freeway exit I heard a noise coming from the front bottom driver side of the vehicle. It started making a constant whining sound especially while accelerating (more accentuated). It also makes that sound while stopped in drive or reverse gear. No sound while on Parked gear. Also, when I opened the trunk the steering wheel oil was overflowing but not bubbling. Could this is the problem ?
Without a detailed checkup a mechanic mentioned it sounds like it is the transmission filter or the transmission, is it a coincidence that both broke down at the same time ?