When people talk about 7.5"/8.8"/9" rear ends being able to handle a given amount of hp/tq, what are theyactually refering to? When the rear end goes, what is the weakest link that gives and actually causes failure?

 

Sometimes it's the axles twisting. Other times, the housing will flex, destroying internal parts. Most times, the gears themselves will chunk.

 

and when they are talking about torque limits. That is only a rough guide line.

You can usually cheat those limits with a lighter car and/or poor traction tires.

Manual transmissions are also harder on rears than automatics.