I gutted my new Durango and installed 2-3 layers of soundproofing. I also upgraded the sound system (I will post a separate thread about this). I used STP products, which are both better (according to DIYMA) and cheaper than Dynamat, which I used on 2 previous vehicles. I am very pleased with the result. I measured SPL before and after, which indicated a 15dB reduction in noise. I treated the floor, doors, liftgate, and hood.
I used 1 layer of STP Gold vibration dampener and one layer of STP SPL04 sound deadening closed-cell foam under the carpet.
The doors and liftgate were treated with 1 layer of STP Gold and 1 layer of BTP10 (thicker foam than under carpet).
I decided against using any MLV due to the existing OEM soundproofing layers and 3M Thinsulate inside the door panels.
I used 1 layer of STP Gold vibration dampener and one layer of STP SPL04 sound deadening closed-cell foam under the carpet.



The doors and liftgate were treated with 1 layer of STP Gold and 1 layer of BTP10 (thicker foam than under carpet).


I decided against using any MLV due to the existing OEM soundproofing layers and 3M Thinsulate inside the door panels.