proper operation of four wheel drive

[peterperr]

heres my query, and i must say, after reading the owners manual and call GM customer assistance, i am still unclear on this one. but, here goes. my 04 chevy blazer 4wd two door ZR2 has a push button transfer case. buttons are for 2wd, 4wd hi and 4wd lo.

 

i dont have the auto four wheel drive option. anyway, when should i be using the four wheel drive hi mode. i am clear about 2wd and 4wd lo. but 4wd hi perplexes me a bit. like if its raining can i put it in. do i have to be going a certain speed like over 40 to be in 4wd hi and should i transfer out of it at low speeds. just dont know, any help anyone.

[chevroletmb]

4hi can be used in any slippery situation at any speed