I'm new to the forum, but it appears this site is a great resource for Frontier info.
I just experienced the failed fuel sending unit and had that replaced under warranty the other day, but have an issue that they thought might be related. After a cold start, my truck emits a medium pitched groaning noise. These occur while I'm driving around 20-30 mph in 5 second or so intervals. After it does this two or three times, the groaning stops and the truck continues on fine.
It may be coming from the rear, but the sound isn't very directional.
The dealer didn't notice it (go figure...) but mentioned it may have been because of the FSU. However, it still does it exactly the same after the repair.
My truck is an '07 KC 2WD. Thanks in advance.