strange "tone" sound from 3.4 engine

ok the truck is 2wd and runs great and has no issues but I notice a sound or "tone" that I can only describe as the test pattern tone you hear when a tv channel goes off the air.

its not very loud and is only heard at highway speeds when the engine is maintaining speed or accelerating so if I reach the top of a hill so the engine is unloaded, it goes away until the engine has to maintain speed again and it returns.

if I had to guess I would "assume" its an exhaust related sound yet there are no signs of any exhaust leaks anywhere.

any insights out there what this could be?

 

rear end or a bearing somewhere? cant pinpoint where its coming from when driving at all?

 

doesn't sound like a bearing.

it sounds like under the floorboard, exhaust or tranny maybe, definitely not from the front or rear of the truck and its not really a bad sound like something is wrong but more like a harmonic "tone" or "drone"

no excess noise to suggest exhaust leaks and tranny fluid is good but I will be flushing it soon and replacing with synthetic

truck only has 115k miles with auto tranny and 2wd

 

so what is the remedy? check and replace rear fluids?

is it something to worry about?

 

ok, well im smart enough to know my limitations and rear end issues are not something I have the tools or experience to handle.

I guess I will have to go to a rear end shop and have them check it and fix the issue.

im hoping it just needs to be shimmed correctly to reduce the amount of excess play that is causing the noise.

anybody have a guess as to what it costs to have someone do that?

 

so pretty much your saying im looking at $1,000 to have the rear end rebuilt

if its really the R&P then its toast anyway so I could just ignore it until it gets worse

 

run her till she blows and buy a complete third to slap in you can choose gear ratio and have a locker or lsd put in for a little more than rebuilding one you have after labor. http://eastcoastgearsupply.com/i-788575-tacoma-8-4-non-eld-t100-tundra-3rd.html

 

thanks guys, yep im gonna let it go until its shouting at me, im still not 100% sure its whats giving the tone anyway, it could be the tranny whining.

its not that noticeable except for my OCD about things like this and you have to turn off the radio and be completely quiet just to hear it.

 

Mine does it too, I just assumed it was something to do with the intake. Like you, it ain't getting fixed until it is officially broken.

 

I'm in the same boat as you guys. It's been making the same humming/test pattern noise for years, however.