Has anyone had a weird differential noise when below 20 degrees or so?

It increases as my speed increases much like you would hear when a PS pump is low. I can switch to 4HI and it goes away sometimes till you switch it back and sometimes it will come back before I switch it back. I have read about the whistle sound under the hood when below 20 degrees, I have that too but this is different.

Anyone?

 

Are you sure it is the diff. When in 2wd, the 04+ front axles are not moving, therefore there would be no movement at all in the front diff. Are you sure it is not a stuck or bad IWE or solenoid. Those will cause a noise that goes away when it is shifted to 4wd, but if yours is coming back while in 4wd, it is unlikely that problem.

 

It almost sounds like rubbing cold rubber together...I'm not familiar with the acronym IWE but assume you are talking about the solenoid that shift the TC on the fly. I said DIF but it sounds more like it's coming from the TC because the sound is close to the cab. Normally when I hear it, shift to 4HI makes it go away but today at lunch it came back just before I switched it back to 2HI.

It kinda sounds like a dry pump or something rubber rubbing...

 

I'm only 2WD but I also have a strange noise when it's cold coming from the front.
I'm baffled as to what it could be, but it's only when I'm just starting to move, basically at an idle speed. It sounds like gears clanking kind of.
Any ideas?

 

The IWEs are the front hubs at the wheels. They have a default position of locked. When the switch or shifter is in the 2wd position and the engine is on, vacuum is sent to them to unlock them. In some case, through problems with the IWEs, vacuum lines, or the solenoid that sends the vacuum, they do not unlock in 2wd. This causes a grinding noise from the hubs, except when you put the truck in 4wd.
As you state it comes back sometimes when in 4wd, then that would not be the problem. Also as the front diff is not rotating when you are in 2wd, would make me think it is something else, Transfer case, engine, torque converter, or transmission.

 

Ah ok...this doesn't sound like it's coming from the wheels, more under the truck. Coming home this evening I made a point to listen and opened my door as I drove and it sounds like the transfer case to me. I tried again switching it back and forth with several minutes between and it never did it in 4HI only when I switch it back to 2HI. It's due for an oil change so I will have the tech check fluid levels etc and ask if they have an idea what it might be.

Thanks for the replies...

 

Would that be the same on a 2WD? I wouldn't think so since there's no locking/unlocking going on...

 

If I remember correctly your hubs unlock with vacuum, so therefore when you truck is turned off the hubs lock, even in 2wd. When you start the truck and if you are in 2wd the hubs should unlock when you start the truck. If there is an issue with the solenoid then it won't and that would cause a grinding noise.

Edited to add, sorry, I misread your question, Kingfish answered the question correctly below my post.

 

As you do not have a front diff etc, then yes it would probably be in the same area, although you do not have a transfer case.

 

An interesting development to the noise. We got some snow and windy conditions here last night and this morning I go out to run some errands. I put it in 4HI since the roads are pretty slick and drifting and I feel like in 2HI. The tail end comes around and I feel no front pull. I have the factory locking rear dif that engages in 4W so while in 4HI it's actually worse than 2HI. I pull into a parking lot not yet plowed to see if I can get front wheel spin...nothing. Now all my previous 4WDs I could do this and it just doesn't feel like the front is doing anything. I can hear it clunk into each range but nothing feels any different. I tried 4LO and again, the rear comes around and I can barely move. Something ain't right here. The dealer is closed today so I will have to let it stew in my head all weekend!

 

Well, I didn't get it to the dealer today but I did crawl under while my wife switched to 4HI and 4LO then back. I checked the TC solenoid and it appears to be working. The front shaft and half shafts are turning when in 4 HI/LO and stop when in 2HI so I think it's leaning more toward something in the hubs as kingfish suggested. Any more info on how these works? This morning the noise in 2HI was crazy! Switching to 4HI made it go away. The more I hear it, it sounds like a gear with fine teeth. Kinda like the older FORDs with the fine spline hubs and gears on auto and locking hubs. Very strange why it does this so bad when really cold.

 

If I might, let me correct one thing in your statement above. A true "locking" rear diff is not available from Ford. What you probably have the "limited slip" diff - which does not engage or disengage with the transfer case. It engages anytime it detects slip between the rear wheels - regardless of 2WD or 4WD.

 

First off, thanks for pointing that out. I should choose my words better because I know it isn't a true locker. I was under the impression that it didn't engage until in 4HI or 4LO.

 

Nope, it's always active. That's why I had so much fun doing donuts in the parking lot at work at 5:30 this morning with the fresh snowfall we had.

I don't understand why your fronts aren't engaging though. The back will fishtail a bit if you really get on it in deeper snow though, in 4x4 mode.

 

Come to think of it I did a burn out one day at work and left TWO big BFG marks.

Well, as far as I can tell from reading around here and the net, it's the IWE actuator under the hood that controls vacuum to the hubs. It is a known problem and it all points that way.

Mine will fish tail as if it were 2WD in any mode and on 1" of snow. I knew as soon as I took off on the light snow we just had, that something just was not right. Usually you can feel the fronts pulling and they did nothing. I was pulling out of a side street on a slight incline and I could barely get moving, LIKE a 2wd.

From what I've read and now understand how it all works, it all makes sense. The noise, the non-functional front wheels in 4WD. It has to be the actuator or the IWE's themselves. The noise I get is really BAD when it's cold (below freezing) and one of the things mentioned in the TSB is vacuum lines from the actuator getting contaminated with water. So...the vaccum has to be applied to the hubs when the truck is running to unlock the hubs and hold them unlocked. When the dash switch is set on 4HI/LO it cuts the vacuum off and the hubs lock. When mine is cold, it must have water in the lines that freezes and won't allow the hubs to fully unlock when I start the truck in the morning and THAT is my weird noise. So once the temp is back up, it thaws and allows the hubs to work in 2wd but since the actuator is bad, when switched to 4HI/LO the TC case solenoid engages the front diff and axles but the hubs won't lock.

Now, having said all that, I'm not sure why my noise, when cold, goes away when switched to 4HI if the actuator is bad....