I have a 1998 f150 and I try to put it into 4x4, i flip the switch, the lights come on, however im still in 2wd. If i leave the swith on 4x4 high or low and begin to drive my engine boggs down. Once I put the switch back in 2wd the truck runs fine. Any suggestions on what the problem might be?

 

I believe these are run by vaccum. Check for vaccum leaks. There is another part on your accuator that looks like a fork (thats the best I can describe it) but I have seen those go bad and do similar things you are describing. Maybe somebody will know what that part is I am trying to describe and chime in for better details.

 

Just about all of the time these issues are vacuum related.

 

i went through this check and re check ur vaccums, also how does you heat work?

 

The part that is of real concern is the engine bogg.
4X4 should never bogg the motor.
Either the front engages or it dosn't.
If this is what is happening, I would suspect something going on in the transfer case like has it ran out of lube etc and binding up.
The dash light comes on from the firewall solenoids no matter what the transfer case does internally after the case motor turns to either the first 4H or second 4L position.
Good luck.

 

My heat works just fine, im thinking that it would just be a vacum leak somewhere.

 

My 01 Ford would not engage when it was only 1-2 years old.
It was the arm on the top of the front axle housing. It can be removed if you bend it a little without removing the entire axle. Clean the spline and grease it ALOT before reinstall. Never had a problem since.
Unknown why engine would bog. Remove two vacuum hoses at the actuator on top of the axle. Have another person engage and disengage the 4 wheel drive and feel the vacuum switch from hose to hose if working properly.
Could also be the electric motor on top of the transfer case.