I see noticeably warmer trans temps with my billet grill in place. It's up to a 20F difference. I keep in in OCT-MAY for reduced cooling and also rock protection, then remove it for the summer towing season.
I have a trex billet grille on my 01 E350,what I did was take a old antenna and mounted it to the hood relase latch ,the end of the antenna sits above the drivers side headlight, I put a piece of rubber hose on the end of the antenna,all you do is pull the antenna to the right and it opens. Hope this helps
My grille came from SMB, fine cooling. I use a small loop of 1/8 in. parachute cord, hanging from the latch, just slightly thru the billet, and hooked w/ a stiff bread wrapper style twisty.