kevingmc14

I've got an issue where I'm getting a hum/droaning sound at speeds between 50-70 mph in 2wd only. Switching to 4wd cuts noise off instantly. Then I'll switch it back to 2wd and drown like pulsing noise fades back in at a faster rate then slows down to 1-2 second intervals...only at that speed range. Rather annoying. Any ideas???