Originally Posted by loveracing1988
Don't worry about the gears. Five hundred miles is a lot more breakin than they get when they are being tested. That would be less than 10 miles and it then goes straight to the capacity of the axle.
Testing is under no
load when it is done.
Regular driving load for the first 300 miles is not the problem unless excessive speed/RPMs come into play.
Towing puts load and increased heat into the equation.
Your 300 mile initial break in was to let the gears temper/meld, that is heat up and cool down without over heating.
New gears or gears under load will generate more heat. Thus the Tow break in in addition to the initial 300 mile break in.
The other issue is if you overheat those gears, transmission/axle, you can damage/overheat the fluid. That would not be good for the life of those items.
The engineers put those two break in requirements into the manual for a reason.