iadapters went to autozone to buy a shorter antenna because I'm tired of mine smacking the garage when I pull in, well of course it won't fit, I tried searching but opulent find a definite answer or website. does anyone know where to get an adapter or what size threads the stock antenna is so I can fab an adapter. thanks

 

All that concern,work,effort, i would measure from the floor up to the garage, door,subtract one inch,cut the antenna at that height,and be done with it. You're not going to find a new antenna the right height anyway,cut one,cut the other.

 

All Sales 6202 Hummer Antenna Adapter:Amazon:Automotive

And than get whatever antenna you want...

 

Skaggs-
happythree is spot on here.
Stock radio antenna on the truck fender is not a loaded antenna.
I cut mine years ago, right below the height of the roof line and it has been just fine.
No weak signals or channels not coming in.
I also had a small black plastic cap that I glue on the cut tip.
looks factory and works.