captainron19

2005 Ford F150 FX4 8Cyl

Some time ago had an issue with a metal on metal grinding sound coming from front axle area.

The noise seemed to happen mostly when going uphill when the truck was under a load. It would stop as soon as I let off the accelerator. After some trouble shooting found the problem definitely to be something with the 4wd accuators losing a vacuum and the 4wd attempting to engage..... apparently a common issue. I also did some troubleshooting by driving up a hill where the sound would always happen but in 4wd and the sound did not happen at all.

The first step i took was to replace the accuators themselves but it did not fix the problem (figures I took the most expensive route first) Next I replaced the solenoid for the system along with the vacuum hose assembly going to both hubs. After doing that the noise stopped and truck has been quiet for over a month.

Yesterday I towed my boat for the first time since making repairs and the noise returned. It only happened when I was driving on the highway and kept happening when ever going up a steep incline. After i unhooked the boat I drove the truck quite a bit including going up more hills and the noise did not happen at all.

As far as I know I have replaced all parts of the 4wd accuator system and it did seem to work because no more noise but it is still happening when under a heavy load (towing boat).

Anyone have any options I can try now ?

Crazy4x4

You probably have a vacuum leak. Most likely on one of the vacuum hoses to the IWE's.

captainron19

I just replaced them... I guess my next choice may be the hose going from the manifold to solenoid.

rkneeshaw

Is it this sound at about the 0:40 mark:


I have that exact sound, about to begin looking for vacuum leaks.

Based on the 4x4 system diagram (somewhere else on these forums EDIT: here it is https://www.f150forum.com/f4/4x4-tro...g-guide-39789/) it sounds like the only thing you have left to replace is the vacuum line from the manifold to the selenoid, as you suggested.

If you think about it, that selenoid basically only opens and closes off the vacuum line. If you have a vacuum leak anywhere between the manifold and the IWE's, anywhere along that chain of hoses, it would effect vacuum pressure and probably the operation of the actuators.

EDIT: and looks like there are some check valves in the mix too, but I'm not certain what effect those would have on vacuum.

captainron19

Yes that is the exact sound. talked to someone and he said that since it seems to be happening now only when towing the boat up a hill it is probably the vacuum resevoir failing (mounted near the solenoid)

Just got back from the ford parts and ordered a new resevoir and also brand new check valves going to the manifold.

Crazy4x4

You might need new IWE's again, it sounds like they might be trashed already with all that grinding.

captainron19

So I picked up a new vacuum reservoir the other day and put it in .... quick 5 minute job. When looking at the old box I put it on a vacuum tester and it would not hold a vacuum. Found a cut in the rigid vacuum line coming out of the old reservoir box. Once replaced I hooked up the boat and took it on the highway for a few miles and not a peep out of the front hubs.

Only thing I can think of is I must of originally had a bad solenoid or large leak in one of the main vacuum lines cuz when i replaced those two items the noise stopped except for when towing the boat. The break in the vacuum line coming off of the reservoir box was probably small enough to still hold enough of a vacuum under normal driving conditions but when I added the weight of the boat it would not hold.

Thanks to all for the input and help .