2008 4.7 5-speed auto 33K miles....

Just started a couple of days ago...I hear a weird hissing (best described) noise when accelerating. It seems to happen in the lower rpm range. When I give it about half throttle or more, the noise goes away. You can hear the noise rise and fall with the throttle, but again, it only seems to be happening below 2000 rpms....When I am stopped and give it gas, I do not seem to hear it.

Not sure if it is exhaust related, rear end related, transmission related??
Any ideas or thoughts??

 

What kind of intake you got? Sounds like an intake dealio...One of them there noisey ones???

 

Thats what I would guess. Does it sometimes almost sound like a blow off valve?

 

Stock airbox.....K&N drop-in.....and it just started. I have had the truck for a year and a half....seems to be coming from the rear of the truck...

 

bump - anyone??

 

It could be the rear end although it will typically make a whining/whirring noise. Has your truck recently been regeared or had any work done to the rear?

 

I had 4.10s installed about 9K miles ago.

 

I would think that an issue w/ it would have come up before now then. Who did the install, maybe call them and describe what you're hearing. Also check your differential fluid level, hopefully it's nothing.

 

I have the same truck as you only auto with close to 20,000 miles and have also noticed this hissing while accelerating at lower rpms. On mine it sounds like it's coming for the passenger side under the hood maybe. It just started one day and has kinda bugged me. I was gone for 2 weeks and just got back and haven't noticed it in the past couple of days so I'll have to see if I notice it. If this is the same problem maybe someone will come up with an idea. I'll look mine over tomorrow.

 

Mine is automatic as well - the 5-speed auto......kind of weird....