I replaced mine with a Fantastic Vent fan. I bought the cheapest model, one way, 3 speed. It required removing the entire stock fan assembly, outer cover and all.
It took a lot of scraping and pulling to get the old sealant off the outside, then it was a matte of removing the screws and prying the old assembly off of the putty sealant.
The new fan comes with a foam seal that I used in place of putty sealant. If I did it again, I'd buy a roll of the putty to use.
The inside portion of the fan had to be trimmed a little to make it fit the angle of the roof, but tht was easy with a sharp, stiff knife.
The new fan works GREAT compared to the dinky stock fan. A world of difference. I now wish I bought one of the portable Fantastic fans too. Right now I'm laying inside my TT, parked in Moab, Ut. Not enough generator wattage for air conditioning, so one of those portables would be really nice right about now.
Even if it's a dry heat, it still makes you sweaty without enough moving air.
2011 Dodge Ram 1500 HEMI Quad Cab
2011 Jay Flight 26BH