So as I was leaving work today, a snowplow decided to come down the road and shovel a big mountain of snow right in front of my truck. I tried going over the mound in 2wheel, but shortly lost grip.
So I clicked it in to 4 wheel, feel the light thud of engagement, and I start to drive. Except nothing happened. Except for my back right wheel being the only wheel spinning. I stopped the motion of the tire, switched into reverse, and again, got one wheel moving... the back right. After I switched back into drive, I finally got the back left wheel going but still no 4x4. I tried 4lo...nothing. So I got out, and started using my ice scraper to shovel whatever I could away from the tires. I got back in after about 5 minutes, selected 1st gear, and hit the gas.
This time, all 4 wheels were moving and I was free.

Why was there about a 10 minute delay in the 4wheel engaging?

 

as you were moving from 2wd to 4wd, did the truck move at all? if not, then that is probably why..... when you shift into 4wd, the hub solenoid dumps the vacuum to the hubs, and that allows them to engage (if the actuator ring is lined up with the hub gear to engage). if not, then the front tires must move to allow the parts to line up, and engage. the light "thud" you heard was the transfer case engaging, so that is just fine. try it a few more times.... im guessing that everything is just fine.

 

thats very interesting. yesterday my 4x4 was acting up too. when i shifted "on the fly", there was just a nasty grinding sound for a few seconds. i quickly turned the **** back to 2wd. i was only doing 40km/h. i slowed to 20km/h and tried again with the same result. i finally stopped and shifted to 4x4, it did it with no hassel and there was no clunk from the front end like there is sometimes when shifting while parked. it worked fine the rest of the day.

any ideas?? is it something i should get checked out or possibly just snow/ice under there on the moving parts??

 

it sounds like the same thing as the OP....... a lot of people think you can just "shift on the fly".... i know, thats what ford calls the system, but honestly...... how easy do you really think it is for gears to mesh when some are turning, and some are stationary. i try not to engage 4x4 unless i am stopped....afterall, if your already moving in 2wd, then is there really a need for 4wd? thats just my opinion.

 

I have the same experience with my '05. It really shifts best at rest, and rocking it slightly sometimes helps. It's like the old manual hub days-by the time you realize you need 4x4 it's too late. Brian

 

The manual states that you must be stopped in order to engage 4wd. It also states the tranny should be in nuetral

 

For 4 Lo, yes. Not 4 Hi.
"Move the 4WD control between 2H and 4H at any forward speed up to
55 mph (88 km/h)."

 

and make sure all 4 tires are at the same speed

the rears going faster than the fronts can break things

 

I was able to rock back and forth while shifting from drive to reverse and back.
So the front wheels were moving enough. And when it finally engaged the front, the truck wasn't moving anywhere.

Everything works fine....for now.