I have a dilemma that has been twisiting around in my brain for some time and I can't seem to work it out. Here is the scenario, and problem:

1. I have a brand spanking new PuddyMod Stage 2 differential with OEM diff unit and Richmond 4.56 gears.
2. I have a (soon to be) freshly re-built F20 with pretty much stock everything

Problem:
The recommended break-in for the diff is to drive fairly for the first 300 miles with the instructed oil changes. Here is where it gets interesting; in terms of breaking in a new motor in order to acheieve proper ring seal I have heard first hand (and read) two schools of thought. The first is that the motor should be babied for the first few hundred miles, then stomped on pretty hard. The second theory is that the motor should experience 4-5 hard 4th gear pulls (with a significant load) from 3k-9k after only a minimal amount of new miles in order to acheive proper break-in.

If the former is true, then all is fine and both the motor and diff will be broken in utilizing the same theory and level of abuse in the initial few hundred miles. However, if the latter is true, then how am I supposed to baby the diff for the first few hundred miles while simultaneously giving her several good hard runs under a significant load.

Any thoughts or advice? Real world experience with this issue would be super helpful.

Thanks.

 

It's the hone on the cylinders(and rings) that need to break-in on today's engine. To do this I have always done a hard break-in, this is WOT to about 70% to 80% of red line in the higher gears(3rd, 4th or 5th) and then let it back down with 0% throttle. If you have hills where you live, that is the best place to do this. Don't try this in the city.
Here is a guy that has done this a lot of times
http://www.mototuneusa.com/break_in_secrets.htm

ROD

 

Thanks Rod, I've been told the same thing by several other people too; what about the issues regarding the diff though? I'm not sure how to do a hard break in while simultaneoulsy taking it easy on the diff.

What about driving easy for 100 miles to break in the diff, then doing a hard break-in on the motor? Would this degrade the overall break in?

 

with regards to breaking in a new diff, i'm not too familiar with that. as far as the motor goes, rrounds is right. break it in hard. me personally what i would do is turn on the car with any off the shelf oil and let it idle. dump that oil, pour in new oil and break it in on the dyno.

 

Hit vtec on my test drive with 5 miles on odometer and haven't stopped since. My motor seems to be very healthy.

 

Just don't bang the gears, you want to put the "engine" under load and vacuum. You don't put out enough power to hurt the gears on some WOT pulls. Just because you vary your speed doesn't mean your being hard on your diff. Hell in my old drag car(with 5.13 gears) they went in and on the first pass went 11.47@124 mph. You wont put your rear end gears under that type of load doing some WOT runs.

ROD

 

Agreed. Break it in hard.