2003 civic grumbling noise
 

I have a 2003 civic with 39000 miles and i have noticed that when i turn on
the ac and drive with it on my car makes this loud grumbling noise
underneath the hood and i can feel the vibration under my brake pedal.
The noise usually occurs when i have taken the car into fifth gear then
had to slow back down. although it does occur at slow speeds also. The
noise is reoccuring and does not last long, maybe 5-15 seconds each time.
I took it to the Honda dealer twice and they dont know what is causing the
noise.
I recently had 1st and 2nd gear redone (honda stated it was bad from the
factory) then I had to get a tranny overhaul because the honda dealer
claimed they put it back together wrong the first time and placed the
engine mount block in wrong. any ideas on what might be causing the
grumbling noise?