Hi. I have a 1997 Toyota Tacoma. It's not my daily driver but I do drive it every now and then. Sometimes, but not all the times I hear a pretty loud knocking noise coming from under the bed, possibly around the muffler area when I'm in a low gear accelerating, or in a low gear going up a hill. It doesn't do it all of the time, just occasionally. It makes the noise as I begin to accelerate (for maybe 2 seconds), but as I pick up speed in the same gear it goes away. I'm not a mechanic, so I was wondering if anyone on here that was pretty knowledgeable with these things knew what it probably is?

 

Could be one of your exhaust hangers is broken and the pipe is hitting the frame. Crawl under there when the exhaust cools off and shake the pipe with your hand, should be pretty easy to find.

 

I shook it in several places and it felt real sturdy and everything looked good under there. I don't know what it could be besides maybe the cat. converter and I don't know how to tell if its that or not.

 

Eyeball your U joints

 

My 98 tacoma does the same thing if the engine shakes at all. what I've discovered is that the mount the holds the cat to the hangers broke but in such a way that if you shake it with your hand it'll stay put. But when you start the engine or "dog" the engine on acceleration it's enough motion to make this bad banging sound from what sounds like right under the passenger's butt. I tied the cat to the hanger to check my theory and the symptom went away. I took the rope off though, flames look cool if they come from the tail pipe NOT from under the door. lol