Welcome to the forum!
For whatever reason, the volume on most outside speakers is significantly lower than the inside speakers. Have you tried turning the volume up pretty loud to see if this is the case. On our fiver, the radio has three speaker settings, A, B & C. C controls the outside speakers. Does your radio have these type settings? If not, you might post which stero you have so others that have the same radio can chime in with advice.
Kevin & Janine
2006 Dodge 2500 Megacab CTD 2WD
2012 Palomino Sabre 32RCTS
Pullrite Superglide 16K Hitch