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Hello all. I have a 2018 3.5L F150 with 46,000 miles on it. I've had the cold start rattle for a year or so, but in the last month or two the truck has developed a rattle coming from the engine compartment when I'm driving down the road that sounds like bearings on a pulley going bad (i.e., like rocks being shaken in a can).

The odd thing is, if I ease up on the accelerator, the noise will stop temporarily, then resume a few seconds later, then stop again when I decelerate. If I'm in cruise control, I can make it stop temporarily by slowing down 1 mph.

There seems to be no change in performance and gauges are all good - just the noise. No connection that I can tell to whether the engine is warm, cold, going 30 or going 70. Does it in all types of weather, AC on or off - no difference.

I've heard of F150 noises that begin when decelerating, but mine stops upon deceleration.

Anyone else experiencing this problem?

Thanks to all.

David
 

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2021 Powerboost Platinum FX4 Kodiak Brown.... Oops, I mean 2022 Powergrid KingRanch in Shiney White
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Is it 4WD?
Does the rattle go away in 4A or 4WD?

If so, you aptly described a vacuum leak at the IWE of at least one of the two front hubs.
 

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2021 Powerboost Platinum FX4 Kodiak Brown.... Oops, I mean 2022 Powergrid KingRanch in Shiney White
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12,644 Posts
If the rattle immediately goes away when you switch to 4WD, it's an indicator that your losing vacuum at the hub and its allowing a partial engagement of the hub gears.
Or put another way :
2WD requires vacuum at the hub
4WD does not require vacuum at the hub

So if you have the vacuum leak, the hubs are falling out of 2WD and trying to lock. It's very destructive to the hubs to be partially engaged. You are hearing gears destroying themselves. Sounds kind of like put a playing card in the spokes of a bicycle when you were a kid?
 
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