I need to lock my diffs or close to it. I don't exactly want to go with diff spools but I want my diffs to be "tighter" I tried 500k diff fluid which isn't really much more than 100k. I've tried the Ofna diff lock and its just a little more than the 500k. I can still hold one wheel and turn it rather easily. If I get the truck with one wheel off the ground it doesn't have much pull at all.