Deep echoing engine noise in reg cab 2.4L

I realize my breed of Tacoma is a bit of a minority amongst the awesome 4x4s I see around here, but I wanted to see if anyone else has had similar noise issues and done something about it.

My truck's got a brand new muffler and its nice and quiet on the outside while its running. However on the interior during acceleration there's a deep, echoey noise from the engine. I don't feel like its an unusually loud noise indicative of a problem, but it is just loud enough inside the cab to be annoying. Does anyone have any relatively inexpensive suggestions?

The underside of my hood is bare. Would some sound dampening material installed there make a difference?

 

Bump...anyone?

 

How is the exhaust system built?
Is it the factory system, or is it an aftermarket muffler?
Does the pipe still dump behind the tire, or does it dump under the bed?

Some aftermarket "performance" mufflers will have a drone at highway RPM that some people find irritating.
Dumping the exhaust under the bed in front of the axle makes it even worse.

 

Manifold, front pipe, and cat are original. The rest has been replaced with an OEM replacement muffler from my local muffler shop who uses Napa as there parts supplier. Dumps behind the rear tire. Thing is the original exhaust system made the same amount of racket in the cab, too. I think it's just poor quality (or lack of) noise control installed the cab. There's no sound dampening material anywhere in the truck, not even under the carpet from what I could tell just lifting the carpet up behind the bench.

I think the drone comes from how the engine noise/vibration travels through the frame/body because unlike how an exhaust leak creates a noise you can hear coming from a certain direction, this sounds like it's coming from all around me.

 

I missed your question before, yes it does. Only thing I've changed on this truck is the exhaust (see above ^) and the spark plugs. Everything else is stock.

 

Okay, ya... you hit the nail on the head with the lack of sound deadening.
Even the 1st Gen Tundras were modestly insulated... the Tacoma retains too much of it's 1972 roots.

 

Thanks man, that's kinda what I figured. I feel like mine's about the same noise level as my brother's old '75 hilux was. Anybody have any ideas where to start with putting in sound deadening? Where might I get the best bang for my buck? Under the carpet? Hood? Door panels?

 

Floor panels are a good spot, but the carpet helps some.
Not sure what trim level you have, but on my '08 Regular Cab, there is NOTHING on the rear wall behind the seat.
I had a '94 extended cab... I don't think there was anything under the plastic trim.

The roof is another good spot. That's a big sounding board with nothing up there.

 

So before I start with sound deadening insulation, I'm going to try and install some exhaust dampers to see if that would make a difference. Trouble is I'm having a heck of a time finding where I can acquire some dampers. The only place I've been able to find that I'm able to buy them is from a Ford stealership for $60+ a pop.

I say forget that, how hard can it be to make them. I've found a couple photos of exhaust dampers, but I wondered if anyone had any ideas on how one of these could be made. It doesn't seem like it'd be that hard, but then again I don't have access to a welder.





Edit: I made one out of an exhaust clamp, a 2 1/2" x 5" U bolt, and about 50 5/16" x 1 1/2" Fender Washers. I haven't tried it yet, though. The whole thing weighs between 2-3 pounds depending on how many washers I can cram onto it once it's on the pipe. I bought enough to make two, so I'm gonna try putting 'em on when I can get a buddy of mine to help me find the best location to install them.

 

Installed one of my DIY exhaust dampers last night, and I think it works. I don't have a way to quantify the results since I don't have a dB meter or a scan tool that monitors vibrations, but it sounded and felt quieter in the cab. Before I installed the damper, my rear view mirror would vibrate so much that you couldn't really see out of it. Everything was just a blur. After installing it, there's nowhere near as much vibration in the mirror. So that tells me it's probably not just a placebo effect I'm experiencing.

I've gotten a few suggestions on how to figure out where the damper will be most effective so I'll probably experiment some with that this weekend and maybe I'll get better results. Plus, I have another damper to put on.

 

My 2.4 didn't make that noise, but I will admit that they are noisy. Mine was VERY VERY rattley.

 

I'm not a physicist or an engineer, nor a genius, but I would think metal on metal on metal would create a rattle.

 

I don't claim to know everything about it as I'm not a physicist or an engineer either, but i understand it somewhat because of a Mythbusters episode. The increased mass strategically placed where the pipes vibrate the most decreases the their resonant frequency. That resonating is what translated to the exhaust droning I was hearing in the cab.

Also, everything's tightened real solid, so it's not creating any new rattles.

 

Edit: Ken beat me to it

 

Gotta be quicker on'da draw, pard'ner!

My dad was a mechanic for Toyota back in the late 80s and 90s and he said he'd see only see 1 or 2 trucks a year that did this. It's not a common problem and when it is a problem it may be worse on some trucks than others so not everyone who has one with this problem would even recognize it because it just sounds like exhaust noise. But when the exhaust noise is louder inside the cab than it is outside, it's probably due to this problem. That's not to say these little trucks aren't rattley little tin cans, because they are!! Mine just happened to rattle the rear view mirror like crazy during acceleration and at steady highway speeds and it would produce a low droning sound loud enough to be irritating to me. It may not even bother some people.

Now, it's all but gone except for an extremely brief period while I'm accelerating between 10-15 MPH. It has more to do with the RPMs than the vehicle's speed, but my truck don't have a tach, so I dunno what the RPMs are for sure. Probably 1800-2000. I'm gonna see if a second damper can resolve it this weekend.

I know this doesn't accurately quantify the problem, but it's evidence to me that I've made a difference. Before installing this, doing 70MPH on the highway, I had to have my radio volume up to at least 18-20 (out of 50) to be able to hear anything. Last night driving at 70, I had the radio at 10 and I could hear it just fine.

 

Not to , but I've decided this thing could still use some sound deadening insulation. I think I'll save up and do that in the spring. Rather than just doing a few panels, I think I'll insulate the whole stinkin' cab.

 

I'm thinking the same thing.

Normal commute to and from work is not bad, but on vacation a couple of weeks ago, extended runs at 70+, it was hard to carry on a conversation (I'm deaf in my right ear so ANY noise in the cab masks the passenger.... that can be both good and bad)... and after a while there is a noticeable "dulling" of my high frequency hearing, indicating that I've been exposing myself to excessive noise levels for an extended period.

Too many years of gunfire, rock & roll, and motorcycles takes it's toll on your hearing.



I'm thinking a layer of Dynamat (or similar) on the exterior panels, coupled with a layer of a more dense padding not unlike carpet padding, with an extra layer of padding on the interior plastics.

 

Some cars have similar dampers from the factory so I'm not surprised to hear it worked. BMW used them on some of the 97-03 5 series cars and on some 7 series models. For sound deadening you would be amazed how well it works. Do the roof, rear wall, and especially the doors. Makes a huge difference. Check out fatmat brand. I used their rattle trap product in my last 5.0 mustang and it worked wonders for about half the price of original dynamat. Even just carpeting the rear wall for a finished look makes a big difference.