So a month or so ago I started to experience and intermittent humming sound that I thought to be coming from the RF. I’ve replaced the RF IWE, solenoid, and the valve from the solenoid. The sound doesn’t seem to be there in 4wd but seems to be there in 2wd. I just ordered new vacuum lines from the solenoid to the IWEs. Can this be the issue? I would assume it has to be Vacuum related because I don’t have a sound in 4wd.

also when the truck is running I jacked it up in 2H and the cv was not spinning, my thought is weak vacuum?

any help? Or knowledge.

2015 f150 lariat 3.5 38k miles

 

Do you have the 4A option available? If yes, run it there for a period, ok to run at hwy speeds as well. If sound goes away (because IWE is engaged), then you know you have a IWE issue.

 

Was the truck warm and drivin for several miles before you got under there? If memory serves all these trucks will start off with the IWEs engaged for the first few miles to warm up the diff fluid and the will disengage. Im sure someone here will confirm.

 

Yea it was warmed that’s why they weren’t engaged when I jacked it up.

 

yea it has to be vacuum or iwe related but already replaced iwe so I’m guessing vacuum

 

2018 + are the years that had the vacuum delay feature to disengage the IWEs, a 2015 to 2017 "MAY" have had that TSB, or may not. My 2017 was one that had it before I bought it.
Humming sound would lean more towards a bearing than an IWE grinding.
Let's start again. Does the "humming" sound like this?

 

sorta sounds like thay but it’s intermittent, so doesn’t happen all the time and only happens when driving down the road not through a parking lot

 

Does it do this when the engine is under any sort of load, going up hill, accelerating?
Fords fix, if everything I've writing is fact, is to pull the vacuum hoses, and cap them off, on trucks with 4A. IWEs will be engaged all the time then.
Or, you can do that yourself and save a trip.
Or, you can pull the power to the solenoid, that will accomplish the same thing
Or, you can drive in 4A regardless of road surface at any speed.
Or, you/we, can go fix this, if indeed it is an IWE.
Who replaced the original? Care has to be taken when installing, if teeth aren't correctly lined up and torqued, chances are new IWE can be damaged.
Would a video be possible?

 

we’ll your gona like this, so I noticed my air box wasn’t on in the back so I put it back correctly, took it for a drive and the sound never happened….

 

LOL!! You mean the vacuum reservoir on the firewall?
I almost was gonna say, bring the thing over if you live around me, and we could tear into it!!