I've had occasional issues the last year getting my 04 into 4WD, but at 270K on the original IWE actuators, that's probably to be expected.
I had new actuators ready to install, but took the truck out for a drive before doing the job. On a gravel road the back tires spun easily in 2WD, I switched over to 4wd and it was much harder to spin the tires- you could tell it was in 4WD- or at least seemed that way. I left it in 4WD and tried turning on a tar road and it didn't seem like it was binding at all. (I have an open diff in the rear, assume the front is the same?)
Anyway, I installed new actuators last night and took it out for another drive afterwords. I put it in 4WD and could IMMEDIATELY feel the binding when turning.
What I cant figure out is why I could NOT feel binding while in 4WD prior to the install. Could I have been in 3WD somehow? (04 Super Crew, Automatic, 4.6L, XLT- pretty basic pickup...)
Well, 2WD actually without limited slip - one wheel can drive at a time on each axle, but it can be either wheel on each axle, so that means any of the four wheels can drive, hence the term '4WD'. There are two causes of 'binding'. One is the CV joints in the front axles on tight turns, and the other is tension induced in the transfer case from making turns on pavement, as one axle completes slightly more rotations than the other, while they are locked together. On a loose/slippery surface the tension is relieved by wheel slip.