2004 Tacoma knocking sound when coasting

Greetings Gents,

Within the past few months my Tacoma has developed a low pitched knocking sound that only occurs when I let off the gas and coast. It also changes in frequency depending on the speed I am coasting. I notice it most when I’m coasting next to a protective wall on the interstate because the sound bounces off the wall.

I have tried looking for where the noise is coming from but I cannot pinpoint it’s location. I put it on my lift and rotated each of the wheels ad the driveshafts but no knocking noise. Which means it only happens when the truck is in gear. I’m too afraid to put it in gear and try pushing the gas while it’s on the lift because that just doesn’t seem smart.

Anyway, I figured I’d get someone else’s opinion online before I start replacing parts that rotate such as U-joints.

If anyone has had this problem or has any clue what it might be I would very much appreciate the insight.

Thanks,