When I purchased the truck it had an aftermarket stereo in it that was dead. I found the factory radio in a box in the back seat and reinstalled that, and it worked. However, I wanted Bluetooth so I installed a spare double din Pioneer I had floating around. I used a Metra 70-1858-1 radio harness. It sort of works... but the sound is not very loud, it's quite tinny, and I am not getting any sound out of the rear passenger speaker. I'm wondering if these trucks have built in amplifiers or if it's using the amp inside the head unit, in which case a 4-channel amp would be a good choice for my vehicle. And any reason why one speaker might not be working or the speaker is just blown? Also, I get an odd thumping/rattling from the back of the truck... I suspect that this vehicle might have come with a factory subwoofer but it's blown or it's not set up correctly since I'm using an aftermarket head unit. Any input appreciated. Thanks.