I've read where you have break in gears for 500 to 1000 miles. What's the consensus? Do you have to, and if so, for how many miles? I'm installing a set of 4.10 Ford Racing gears which are already lapped in.

 

I was told to run mine about a 1000 miles pretty easy to break them in. Thats was hard to do but I did it. Haven't had a problem.I changed the rearend oil after about 5000 miles.Didn't have to,that was just something I wanted to do.Everything still looked good.I now have about 15,000 on them.