Ford: Idle issue, radius arm bushings, alignment specialist

Question
I have a 2006 Mazda B2300 pickup with the 4 cylinder engine /auto transmission which really is made by Ford , just different name plate besides Ranger. I have 21,000 miles on it and have been delaying taking it to the dealer because I know they will say " Can't find any problems ". It has a interesting issue that happens only at idle, stopped and when it is least expected. Out of the blue there will be a loud thud noise from the passenger side of the engine compartment. This happened yesterday , with my wife in the truck, and she thought we got hit by someone. First time it happened I jumped because I thought that was what happened as well. When asked to describe it further , as I am at a total loss to do so , she says it's like a bird flew into the car and got hit. It is strange because that is the only symptom !  Drives O.K. , idles O.K. etc. As you can see I do not drive the Truck very much but it has done it , at random ,since it was new. Never got to the point of happening enough to show someone what it does or making it repeat on command.  I have one year left on the warranty and want to get this figured out while they have to repair it.  Any ideas ?  Questions ?  Pull the hood and it says Ford everywhere. Mazda dealer once told me that they could not get good info on their trucks made by Ford for some unexplained reason.  So might as well cut to the chase.  Thanks so much.

Answer
There were some contact noises on the right front from worn radius arm bushings, springs and torsion bars.

Look for contact spots( shiny areas) or dusty rust. With a large prybar, check all sway bars, raduis arms and front suspension.

You may have to wait until noise becomes consistent, before it is findable.

You may also try a suspension/ alignment specialist.