It actually makes them about twice as strong. They approach the strength of an open 8 1/4 when they have a clutch type sure grip unit in them. their weakness moves from the internal spider gears to the axle shafts themselves. They're pretty small. As long as you keep in mind what's under the car and drive it accordingly, you'll be ok. I did several burnouts in mine with the 3.90 gears before I pulled it back out and I don't believe it would have ever broken behind the slant 6. Now if I did stupid things like put slicks on it and tried to get it to stick, I'm sure that would have been different.