Im a bit confused. Im rerolling GC. If i get just +40 life. I didn`t hit the prefix just suffix?
I thought prefix was there 100% percent and suffix if the luck is on my side is also there.
Or they are both equal chances?
Are they divided so you can`t hit both like on gloves/helms?
http://classic.battle.net/diablo2exp/items/magic.shtml
When Magic Items are created the chances are:
Both Prefix and Suffix: 25%
Only a Prefix: 25%
Only a Suffix: 50%
Thanks , that answers my question.
This does not go together with English teacher 
edit: does the character level has any impact on rerolls? Or just the ilvl? Cause i have mules and its easier to make the rerolling with them.
The original ilvl only matters with the pgem reroll cube recipe.
http://classic.battle.net/diablo2exp/items/cube.shtml
3 Perfect Gems (of any type) + 1 Magic Item = 1 New Random Magic Item of the Same Type
You can use this formula to get another chance at a Magic Item of the same type. The ilvl = ilvl. This means to use 100% of the ilvl of the input item. It’s important to note the difference between “the ilvl is set to a fixed number” like what happens in some recipes and “the ilvl of the output is exactly the same as the ilvl of the input” as is the case here. So if you’re cubing for +skills Grand Charms, for example, you want to use Charms starting from late Nightmare, not ones that dropped in the Normal Blood Moor. You can use this formula (with an Amulet) to create a +2 Skills Amulet. And you cannot Gamble one before Character Level 84. Be warned however, that the chances of getting that on an Amulet might be very low (considering everything is available) and it might take a lot of tries. Rare Items cannot be used with this formula to create new Rare Items. You can also use this on Charms and Jewels.