If you only have 4 miles on the new gears you should absolutely not be doing 100 mph, or hard acceleration.

Initial beak in should be run 10 soft miles, about 45 mph, stop and let diff completely cool down. Then similar run 25 miles more miles. Then run remainder of 500 miles with light to moderate acceleration, no faster then 80mph. Change diff lube at 500 miles then let her rip.

You have to let the new bearings and gears moving/contact surfaces wear to each other. Because things are new they get very hot very fast and will break down the lubrication of the oil if it gets too hot.

Your new gears can easily eat themselves if your ripping on the gears. After my first 10 mile break in my pumpkin was 180 degrees ( infared thermometer gun) with the nismo finned cover. Temps went down after the next 25 miles to 150, then i stopped measuring.

Just dont want your hurting the best mod you can do to your car

 

Thanks for the heads up, I didn't know that. I only did it very briefly. There are stop signs every mile, so I definitely couldn't keep it up for long. Plus it was 35 degrees yesterday, so I hope it wasn't able to get very warm in 5 minutes. I will definitely take it easy for a while.

 

Keep in mind some drag racing folks (namely mustang drag racers) will say they just installed the gears and beat on them. Big difference is these guys dont usually drive the cars for long periods, short drag runs don't build much heat in the diff.

Sucks your up north in winter, I racked up those 500 miles in a week bc I couldnt wait to rip it up. Wife was surprised when I said "hey, let's go to dinner on the other coast of florida tonight"

 

It has been fairly warm here lately. I had been driving it quite a bit up until I dropped the diff, and soon after it snowed. Driving a lot is no problem. I drive a lot between school and work (both 30 minutes away from my house in different directions). Luckily I have a maxima with almost 220k miles to keep the miles off of my z.

 

this was actually pretty informative.
subscribing. Makes me nervous, I'm in the process of swapping in a cusco rs lsd for my vlsd

 

I don't think I ever mentioned it yet: the install cost me $332 including $80 worth of shims from Nissan. I guess they did have to machine one to get it perfect. Overall it went fairly smoothly. If you plan to take it to a shop I would suggest giving them a copy of the fsm. After reading through it a few times I am fairly confident I could have done it myself. The cost of tools and my time probably weren't worth it though.

 

nissan's shim situation is asinine, and this is not limited to 350z drivetrain parts. shims for many different transmissions have been backordered and hard to get a hold of for years. luckily when i was doing nissan transmissions a lot i had access to thousands of shims for other transmissions. all i had to do was find a shim that was similar diameter and then select the proper thickness. the trans in my car for instance probably doesn't have a single shim in it that came from nissan. they are all from mitsubishi applications.