The car we had enormous trouble with - the screaming was not drowned by loud music, she screamed til she made herself sick, she was a driving hazard. We live remotely and to go anywhere is a couple of hours. At first, we had to use a mild sedative to calm her down - certainly not a first course of action. We only did this with the consultation of our doctor, and we ended up only having to do it twice. Just enough to show her that screaming in the car was not needed. We also at that dr consult ruled out other issues, like motion sickness.
Can you give your lo something to do in the car? something to chew on? DVD? (we have one of these now, it really really helps us, but we didn't get it til she was about 10mo). Umm...it could even have got to the point where it is habit (ours had). If you can find a way for your lo to be calm for a couple short trips, you may be able to break the habit - would your lo be calm if you sat in the back for a couple trips, with someone else driving? even having a bottle in the car?
In the stroller -same kind of suggestions, except here I used to pick lo up and calm her, then put her back again. Eventually the time in the stroller got longer and longer. To this day, I always have the sling in the tray underneath just in case. also - keep moving. My lo still hates to be still in the stroller, because ten she wants out. Lots of toys in the stroller also, snacks anything (hard to do snacks at this age). We also used a dummy and her lovie ALWAYS goes with us in the car and the stroller.