I was told by another source that the reason i can't get out of 4x4 is because the vacuum switch is stuck open. The front axle won't disengage so will replacing the switch fix the problem. Any other comments you may have will be helpful.

 

Depends if the vacuum switch is really at fault...
Need to know what model and year you have to diagnose properly, but in general:

To check, find the vacuum hose that goes to the vacuum actuator for the front axle. Pull the vacuum hose off the actuator and plug it.
1. If the front axle is still engaged, check the cable for binding.
2. If not engaged, then the problem could be the switch or the power to the switch... you'll need to check this with a voltmeter or test light. The switch should be powered when you have it in 4x4 mode, not powered when in 2wd mode.

 

I was mistaken. I thought the front axle was still engaged. I jacked up the front end and can spin the tire, also while up in the air i engaged 4x4 and then couldn't spin the tire.However, the light on my diagram in the truck 4x4 panel says the front axle is engaged. As for the model i have an 87 s-10 blazer tahoe. I also noticed that even though i can turn the wheel when i drive i seems to have a whinning noise. Any suggestions.

Also my brake pedal drops to the floor. I don't see any leaks so i am thinking master cylinder is bad. Do you concur.

 

With regards to your brake pedal going to the floor, if there are no leaks and the master cylinder is still full of fluid, replace the master cylinder.

Sorry, I have no answers for your 4X4 problems.