Thumping/rumble/burbling Noise At Low Revs

[schnoutboy]

I've driven Toyota trucks for over 30 years and have been very pleased with them. I recently traded in my 1991 extra cab v6 4x4 after almost 26 years of ownership. I traded it for a 2014 Tacoma access cab v6 4x4 with a 6 speed manual transmission about 2 months ago. The truck had about 47k miles when I bought it. It is in very good shape and service records showed that the previous owner got the required maintenance done. After a while I noticed that it makes a noticeable thumping/burbling noise at low revs (under 2000 rpm). It is more noticeable when the engine is under load, like driving uphill. It sounds rough, but feels smooth. If I accelerate above 2000 rpm, the thumping is diminished, but I don't think it goes away entirely. I can't tell if it's an engine noise, exhaust noise or something else altogether. I wonder if the sound I'm hearing is actually from the exhaust and/or cat. I didn't see any holes in the exhaust and it looks stock, but it does sound almost like an after market exhaust, more of a rumble/burbling sound. Maybe its always there and I can only hear it more clearly at low revs going uphill. I've searched here and all over the web and haven't found any definitive answers. Has anyone else experienced something like this? Is it an indication of a minor problem or am I in for some major repairs? I don't know if it matters but I do live at about 6000 feet and drive at elevations varying from about 4000 feet to 9000 feet. Thanks!

 

[Mjp2]

I've driven Toyota trucks for over 30 years and have been very pleased with them. I recently traded in my 1991 extra cab v6 4x4 after almost 26 years of ownership. I traded it for a 2014 Tacoma access cab v6 4x4 with a 6 speed manual transmission about 2 months ago. The truck had about 47k miles when I bought it. It is in very good shape and service records showed that the previous owner got the required maintenance done. After a while I noticed that it makes a noticeable thumping/burbling noise at low revs (under 2000 rpm). It is more noticeable when the engine is under load, like driving uphill. It sounds rough, but feels smooth. If I accelerate above 2000 rpm, the thumping is diminished, but I don't think it goes away entirely. I can't tell if it's an engine noise, exhaust noise or something else altogether. I wonder if the sound I'm hearing is actually from the exhaust and/or cat. I didn't see any holes in the exhaust and it looks stock, but it does sound almost like an after market exhaust, more of a rumble/burbling sound. Maybe its always there and I can only hear it more clearly at low revs going uphill. I've searched here and all over the web and haven't found any definitive answers. Has anyone else experienced something like this? Is it an indication of a minor problem or am I in for some major repairs? I don't know if it matters but I do live at about 6000 feet and drive at elevations varying from about 4000 feet to 9000 feet. Thanks!

I dunno, this is a wild goose choir in a double tunnel unless you can get the sound on video both inside and outside.

Maybe a pic of the muffler would help.... stock is a large round cylinder.

 

[schnoutboy]

Thanks Mjp2, I'll try to get the sound. I'm not sure it will pick it up or not. I can hear it clearly but its not very loud. And others I've asked to listen for it, don't really hear it. I'll check the muffler. Thanks!