when it is REALLY cold (my car has been doing this) the transmission will not shift as it normally does until it is totally warmed up, and this can cause this feeling, and it will also not shift normally.

If the idle is off because of a vacuum leak (if the whistling is loud, I would look at this) it may cause an issues (again... personal experience)

I don't know if it is possible to be in low even though the lever is still in high, but does the car feel like it is in low (shifting quick, lots of power)?

I am not positive about anything else, so hopefully disco mike / spike / someone who knows more will inject their opinions

 

How many miles on your truck, when was it's last major service, when were the brakes completely flush, how about the tranny? Have you pulled the front wheels and inspected the brakes, do you have a caliper hanging up?
What brand of pads and rotors are you going to be installing?

 

It sounds to me like a caliper is not fully releasing the brakes. You may have to rebuild the calipers when you replace the pads and rotors.

 

These trucks are full time four wheel drive, not all wheel drive.
The whistling is because you are driving a brick at high speed and not a slippery to the wind car.
How long have you owned the truck?
Squares are harder to push through the air than a circle so it will not coast for very long.
You may have a stuck brake caliper.

 

I bought the Pro Line front brakes package. I think you're probably right about the caliper being stuck. I'll let you know what i find.

 

if it is a stuck caliper wouldn't he be able to get out and look to see if his brakes were red hot, after driving for a while?