4wd won't engage.
 

Hey all: just found this forum...some great info here but search didn't come up with anything. Anyway, 91 4runner, 22re, 4wd, standard.
all of a sudden won't engage 4wd. On a Tuesday it was fine then Wednesday no go. No wierd sounds just won't come on. I can hear a relay or something click when I shift the lever and it will go into 4 low but only rear wheels are engaged. Gotta be something simple due to lack of anything wierd ...just decided to stop going into 4wd. I am in Canada, can cold have any effect??? never did any other year.
Thanks for any help