So last weekend I was performing my annual pre-Pa. state inspection, inspection. I saw that there is what looks to be some sort of solenoid that is part of the top caliper bolt. I was wondering if anyone here knows what it is for. It appears that the only way to remove that bolt to get the caliper off in order to change the rear pads would be to use an open end wrench as it is part of the bolt head keeping you from using a boxed end wrench or a socket on the bolt. Now my truck is a 2011 F150 4x4 with the E-locker rear diff. Here are a couple of pics. showing what I'm asking about. Oh I should add there is no electrical connection attached to this solenoid.

 

I haven't worked with too many rear disc setups but I would assume that is the E brake assembly. I could be wrong. Someone with more knowledge will chime in as I need to go over my brakes soon.

 

Not really sure what it is?? My 2011 had them and my 2014 does not have them.

 

That is a Caliper Damper.
According to the part information: Low frequency noise cannot be suppressed using traditional methods like brake grease, pad shims or quiet kits, which only work for high frequency noise. Effective solutions are low frequency dampers. The dampers are specially tuned to the frequency of those specific applications to help reduce the low frequency noise occurring in the rear calipers.