My basement has multiple cracks in the walls. But theres one that i'm worried about. it extends from the floor joints above down to the slab, its about a have inch wide and light is shining through. Any tips anyone has would be helpful.
You've got a winner here! What's in the other side? How far below grade is your basement floor? You know that this problem will need to be treated from both sides. (I assume that the crack goes all the way through based on your comments) Did this happen suddenly (month) or has it been years?
Someone will need to dig out the dirt outside the crack and repair the exterior potion first. Otherwise you would be defeating yourself as water would continue to work on the crack from the outside. Put a good sealant over the concrete repair and install some sort of tarpaper or tyvek type paper over all the exposed wall.
Then you attack the inside. Knock out any debris you have and scrap wire brush the area. Use a good concrete patch and getit as deep as you can into the hole.
By the way, before you start, mark the floor and wait a month or two and make sure the walls are not moving.