it happened again after i got it out of the shop. i got off the highway and as i was sitting at the lights i heard a loud squeeking from the front. why did this start squeeking after i got off the highway

 

Sounds like it might be the alternator belt. What was your truckin the shop for? Did they replace or inspect any of the belts? I'd make sure all belts aretight and not deteriorated. If any of the belts are new, they might just need to be dressed.