[07GTconvertible]

I think you will be fine. Its not like an engine were you need to seat the rings. The ring and pinion are in totally fixed positions, so 50 miles should be fine.

[UrbanRedneck]

Originally Posted by Whiskey11 I cant think of a reason why you'd have to wait 300 miles. Most of the mechanical work hardening will happen in the first couple thousands of revolutions or the gear. 300 miles seems a bit excessive. In 4th gear it's 1 revolution of the engine = 1 revolution of the tires amirite? (Isnt that the definition of the drive gear?) So 4th gear for a few minutes at 4000 RPM's is a fairly large number of gear revolutions in the differential... How does that not work harden it sufficiently? Of course, I'm dieing to know the real reason why you'd drive 300 miles before getting hard on it. My new rear diff in my 06 Mustang went about 25 miles before the first time I got on it and didnt have any adverse effects. Having said that though, someone enlighten me as to why 300 miles is the break in period for this stuff?

The idea is taht the gears need to develop a wear pattern with each other before they are strong. But stuff is machined better now than it used to be too, and if they are installed correctly and the pattern is where it should be, there should be minimal wearing after that.

Originally Posted by joeice14 Very interested about this have heard mixed reviews myself... I was wondering though if it was bad to run full synthetic right off the bat... I heard that it could back the gears not break in correctly because they are too lubed... Is that bull???

I would call that BS. Some people believe you shouldn't run synthetic OIL in a new engine (which is still debatable), but gear lube? The factory filled it with synthetic and I bet the first time those gears turned was as it drove onto the car carrier.

Originally Posted by daschaffa17 i turned in the car yesterday and they said to have it go through 3 heat cycles before i mash on the throttle. which isnt too bad so i will do that and going to the track the next day

I would agree with that. See below.

Originally Posted by 07GTconvertible I think you will be fine. Its not like an engine were you need to seat the rings. The ring and pinion are in totally fixed positions, so 50 miles should be fine.

Actually, rings seat like the first 15 minutes of engine operation

My take on breaking in gears, I can see why they would want you too, and if you have the restraint to do so it wouldn't hurt, but I wouldn't call it a requirement. I would at the very least heat cycle it. The instructions for the gears tell you how to do that. Basically just drive it for like an hour, then let it cool off completely, then repeat this another time or two and you should be fine. Like I said, if you wanna drive 300 miles it wouldn't hurt, but I think if you do what I said and put maybe 50 miles on them in the process, you'll be fine. Personally though I would probably wait untill the enxt week to go to the track, but I'd test them out on the street first.

[07Bullitt]

i just picked mine up from getting 4.10's installed about 4 hrs ago. got about 20 miles on it from the dyno pulls. they said to go ahead and rip it........so i left the shop doing a john force burn out, those poor stock perillis are not going to last long.