2009 f150 4wd, tinny noise when accelerating.It just started a week ago. When accelerating in two wheel drive mode only. When i switch to 4high while driving under 60 kilometers / hr the noise stops. ANy idea what could cause this?

 

Probably the IWE system, it's losing vacuum somewhere.

https://www.f150online.com/forums/ar...then-some.html

 

thanks for the help, turned out to be a wheel bearing, cost $400.00,

 

must be more wrong than just bearing, noise is back, guess i'm going to ford dealership

 

Read the thread I linked.

 

Does it sound like a rattling noise coming from one or both wheels? Like mentioned above, possibly 4wd hubs trying to engage. Get a vacuum tester, check the lines like the thread says. Or just get you a new check valve, $10, takes 30 seconds to swap out, and it's likely the fault, as they go bad and don't hold a vacuum well under load.

 

replaced the valve ($88 in Ontario Canada), no improvement, guess it's off to Ford, thanks everyone for the help anyway

 

What troubleshooting steps led you to replacing the valve?

 

What valve did you replace that cost $88, Canadian or American? It's a cheap plastic check valve.

​​​​​​​ to properly diagnose read that thread and check the vacuum though.

 

the $88 dollars was canadian funds, purchased from for dealership here in brampton, ontario. part # 6L3Z-9H465-B

 

^^^

 

That's why it was more, you replaced the entire switch. The cheap check valve is motorcraft part# YG429, for my 2010 anyway. It holds the vacuum and only allows air to flow one way.

 

an update on this thread in case it could help others, I gave in and took it local Ford dealership, after 2 days I got the "Actuator assy" (7L1Z3C247A) put in at a cost of $547.32. This whole adventure ended up being a grand, nice. Thanks to all who helped along the way!

 

The hub actuator on one of the sides not holding pressure then, 5 minutes and a pressure/vacuum tester would have told you that. Part is around $120.