Shark Fin Antenna swap, observstions and why they leak

[JimCost2014]

On 4/7/2020 at 3:53 PM, 2018GMC said:

I got a new color matched sharkfin antenna on ebay. Was $17 shipped. I noticed the new color matched one has a cut on the rear of the seal. My 2018 factory black one has a cut on the front with a inner straight flap of rubber to help keep water out. 
 

I took the 6 screws out and swapped covers to keep my original antenna hardware and seal. 
 

The cut on the front is the updated seal. I guess it makes since since the roof is sloped and water would gravity drain out. Of course it would get pushed in by driving and that’s why the inner flat rubber damn is behind the cut. 
 

Great thinking on the seal.

 

My 14 leaked even on dry days, but 16 never had a problem, or my 18.

 

The color match looks so much better, it is like that on our Tahoe, along with the door handles (not the LT truck ones) with the mix of color and chrome.

 

I would do this to my truck, but I do not know of any other GM vehicles that are the same color (different name per division) as mine.

[cbrsilv15]

There's literally one hole for the wires to come in the roof, and only one way for water to get in.  It's not the outer rubber seal with the gap in it that fails.  It's the small foam seal right in the center on the antennae. Put a thick ring of silicone around the hole when you install it and you'll never have a leak.  You can't even see it because the antennae will be covering it up.

 

Same thing goes for the 3rd brake light.  Foam seal leaks, so just remove it and run a thick bead of silicone and re-install.  Problem fixed.