Knivx - I thought the same - we have the "modified". However, I have the 4.77's and the 3rd members that came with them. The splines match from axle shaft to carrier as well as the axle diameter so it HAS TO BE of the same type. That tells me we have the non-modified wide-track version of the 12-bolt. Which means we are similar in strength to a Dana 44 and not the Dana 60 that has been mentioned before. As you mentioned though, that doesn't correlate with gains in power... soooo... weird.