newb here and hello to all,have an issue

i have a 97 s-10 blazer,4.3 vortec,4x4,right around 100,000 miles.

i have 2 issues i cant figure out for the life of me.
1st,i was driving up to the mountains,and i went to put my highbeams on(daytime driving lights never worked)and all of a sudden,my headlights start to freak.they are flashing on and off and i heard a clicking in the glove box.so i pulled out 1 of the 3 relays that are in the panel in there,my lights came back on,but 1 was bright and 1 was dim.
so i replaced all three relays the next day,and my daytime lights started working and everything seemed fine.
after about 15 minutes right back to the same problem..flashing on and off constantly,so i pulled out the relay to the far right like i did the first time and back to one bright and one dim headlight?
i cant afford to take it to a dealer so i have been driving like this all month.

second problem is even stranger,i am on the parkway doing 65,and as i slow down for an exit,this godawful grinding whirring noise comes from either the front end or tranny?
as i sped up it would get quieter,and as i slowed it would get reallly loud.
i had no idea why i did this,but the next day,i put it in 4 wheel high,drove a few feet,put it back in 2wheel high(the push button thing) and it stopped doing it?
but ever since whenever i go over a certain speed it will do it,i cycle the transfer case and it returns to normal.
now the other day i noticed a whirring sound,not nearly as loud and obnoxious as before,but it starts at about 25mph and does not stop.i took it up on the parkway and it no longer does the loud whirring grinding thing were i have to cycle the transfer case,but it just does this low whirring noise all the time now.
i have a 5 hour trip coming up and i dont want a blown tranny on the road.

thanks for any advice or help in advance,i am new here and was a mechanic for a few years..mostly a glorified parts changer,but i cant figure this out,i know little to nothing about electrical things,and very little about 4 wheel drive systems,i just did engine swaps and tranny swaps mostly,brakes that kinda stuff,no real diagnosis stuff.

thanks again for any help as i am broke and dont want anymore problems.

Sounds like you need to replace the relay and the other problem sounds like the 4 wheel drive did not disengage all the way. Going in a straight line try to shift into 4 wheel drive then back out, you may have a vacuum leak. Good luck

Sounds like you need to replace the relay and the other problem sounds like the 4 wheel drive did not disengage all the way. Going in a straight line try to shift into 4 wheel drive then back out, you may have a vacuum leak. Good luck

thanks for your advice and quick responce.i replaced all 3 relays in the glove box,and it worked correcctly for 15 minutes then back to it's old self,i even tried a different relay and it still does the same thing.
i thought you should not change the transfer case while moving,i always come to a stop to change between 2 and 4 wheeel drive.
thats how i make the noise stop when it goes gooofy on me.
short of buying a manual,cause i did not know the transfer case was vacuum operated,that may be the issue,i thought it was all electric?were can i fing out where he vacumm hoses are,hell i'll replace them all if thats the issue.,thanks again.

You can switch from 2 wheel to 4 hi and vice versa at any legal speed. To switch into 4 wheel low and out of 4 wheel low you need to be doing less then 5 mph