Popping noise from underneath a toyota tacoma

I have a 2009 Toyota Tacoma Crew Cab (2wd) with 7000 miles on it.



Last week, the truck started making a popping noise which sounds to be coming from underneath the truck, in the area of the right front wheel, but the noise sometimes seems to travel toward the rear of the vehicle.



Most of my driving is on the freeway, and the noise so far has only occurred on straightaways, at speeds greater than 35 mph. It doesn’t happen whilst turning or going over bumps in the road.



It’s usually just a single “pop” sound, but sometimes occurs in clusters of three or four.



I’ve crawled underneath, looking for something loose or obvious, but everything seems to be as it should.



I posted the above on a Tacoma forum, and some of the good members suggested it might be the mud flaps, and to remove them and see if the sound went away.



So I finally got around to removing the mudflaps. As soon as I hit the freeway - actually, the onramp - pop-pop-pop-pop in rapid succession.



While I was replacing the mudflaps, I noticed that the right front fender was loose; there was a little bit of wiggle if you grasped it and pulled. So I tightened the three bolts I could find, and no more wiggle.



Back into the vehicle and onto the highway, and…no change. pop! pop-pop-pop! three seconds of blissful silence, and pop-pop!



It seems like the problem’s getting worse; I’ll most likely take it to the dealer this wee, but I’d like to have some idea of what I’m in for…



Any ideas?

Does this truck have alloy wheels or wheel covers?
If it has the latter you might removing the wheel covers, drive it, and see if the problem goes away.

Sometimes wheel covers will pop due to wheel flex and can often be solved by tweaking the cover clips a bit.