I've broken a few 742 8 3/4's over the decades. It's always been the ring & pinion teeth. 1.47 best 60' in a 3,540+ lb 360 footbrake car. I've been using the aluminum cases, which may help overall. I believe that weight is a big factor. But it's difficult to pin down why other things, like an OEM cap, breaks before the teeth. Lots of variables. I put a Dana 60 in my 12 second 3,930 lb Aspen and haven't changed the rear in the Dart yet. Peace of mind.