7 1/4 why weak?

There are only 2 versions of the 7-1/4. The open differential and one with a sure grip unit. The sure grip unit was beefier and will take more abuse than the open unit but in the end it's still a light duty built rearend only suited for small low hp engines.

The next step up is the 8-1/4 which is built beefier than the 7-1/4 and it'll take quite a bit of abuse. And step up again to the even beefier 8-3/4 that'll take a lot of beating on

If you lay all the insides of a 7-1/4 side by side next to a 8-3/4 parts you'd think the 8-3/4 was built for a truck and the 7-1/4 for a Plymouth Cricket