Kytann

So I've owned 4x4's all of my life, but most of them have been old. This is my first modern one. My last truck was a Tacoma. The front hubs always turned the axle, and the front driveshaft was always turning. So I got in the habit of just shifting into 4x4 on the fly. Clutch in, shift the Transfer case, clutch out.
In doing this in the winter I would usually floor it immediately to break the tires loose and go into a nice 4-wheel drift. (usually up to about 10mph, then slow down. Hey, it's fun to throw snow from a stoplight)

When I do this on the Ford, let off the gas, turn the **** to 4x4, wait until the information center says it's shifted, then get back on the gas. I hear a loud cluck from the front. Sometimes more than one clunk.

Now at first I thought it was the vacuum disconnect hubs, and that I just had to build some vacuum for them to engage, so I tried shifting at a stoplight, and waiting. Yet still I get the clunk.

If however I change into 4x4 when I am coming up to an intersection, then it seems to engage without the clunk.

So this got me thinking the front hubs must have to engage over a distance travelled? Does that sound right? But I can't think of a mechanism that'd require distance.

So any idea what the clunk is? I thought the F150 was a shift on the fly system, but if I gotta not gas it after shifting than it's not really. I mean it'll do it even when pulling away from a traffic light at the speed of traffic. Just not as loud. When I floor it it shakes the whole truck, and can't be good for it.

TheWhiteBeast

Just part of the engagement. It even says so in the manual. All the shift on the fly fords I have had have clunked but worked every time. Just be glad its a **** now and not the old push button that sometimes took a few well determined presses to work. Realistically you should let off the gas in any vehicle when shifting to 4wd as the gears in the transfer case need to mesh up and accelerating one half of the transfer case while trying to engage isn't good for any vehicle. Just let off the gas for a second, turn the ****, then get back on it.

Kytann

Yeah I do let off of the gas. Most times I do it at a stoplight, so I am stopped and no gas is applied. That's no problem. What I don't like is having to stay off of the gas for like a block after engagement.

TheWhiteBeast

Haven't had that issue but I drive my truck pretty gingerly.

BarryT82

iTrader: (1)

I've noticed that it takes a while to disengage sometimes. I have to drive a little before it drives like it's in 2wd.

2011 Limited #2431

I have the same issue with my truck. It feels as though I am going to grenade a hub when I shift to awd or 4wd if I am on slippery stuff and the rear wheels slip and the fronts take a little bit to engage from a standstill.

Kytann

That is what I am talking about, it feels like it's gonna grenade

5ohxlt

My 12 does the same thing, I found if i give it a short roll out before stopming on the gas it doesn't do it.

2011 Limited #2431

It reminds me of a 92 gmc Sierra I used to drive to plow with. You had to be driving 5+mph for the front hubs to engage. If you didn't engage the 4wd prior to getting stuck you would wipe out the transfer case. So if you even thought about getting stuck you had better lock it in.

Robob

What your hearing is the splines on the vacuum hubs lock onto the splines of the cv axle, its completely normal. Sometimes when disengaging the system one will take a 1/4mi or so to unlock completely if they are stuck a bit.
Personally i try only to engage only if under 35MPH and rpm under 2.5k, it is gear on gear basically so i feel that's the safest way, Def don't floor it while engaging the system, and also engage and disengage it a few times if your not using it for a few months, it helps keep everything free from binding.