Okay, I had 5.13s installed yesterday and I read a bunch of posts about breaking in gears. Basically, drive easy for 15-20 miles at a time without going over 60 mph and let the gears fully cool before taking another 15-20 mile drive. Do this 5 times and then change the fluid after 500 miles and I should be good to go. Anyone have any input or comments on that?

What about the gears in the front axle? I assume they are spinning as well (NO LAUGHING PLEASE!!!!) when I'm in 2wd, but are they being broken in during this process, too? Do I even need to worry about the fronts?

 

Your fronts are spinning, yes, they'll get broken in.

 

When I got mine regeard they told me i do not need a break in just drive it normally. This place specializes in regears. 5000 miles later still no problems

 

I was wondering about break in also. I found a shop to install the gears and when I asked about "break in" he looked at me funny. I told him about the 15 miles then cooldown I read about here. He replied " how many miles did your Jeep have when you bought it?" I said "4" and he then asked" so who broke in the stock gears?"

Unless they do a gear break in with the axle removed, why are stock ok with no break in and aftermarket needs it? My gear guy doesn't do Jeeps he does classic cars and hot rods. Would there be a difference?

 

There is no difference. People have their own theories on everything.


I question why NOT 'break-in' your $1000+ investment for a few miles?

 

In the absence first-hand knowledge, always go with the opinion you know will not do any harm.

As for OEM and replacement gears, I've read that the surface treatment is different. No first-hand knowledge of that, though.

 

I run mine inconsistent speeds with no long drives (20 minutes and shorter) with regular gear oil during break in... then I drain clean insides and replace with synthetic oil (royal purple). Might be wrong but knock on wood I havent had a failure yet.

 

Yes, it is a good idea to break in the new gears as you have described. You'll notice that for the first 500 miles, your new gears and differential will get very hot with the added friction on the ring and pinion contact areas. If you heat up the ring and pinion too much, you could weaken the metal and cause damage. After the new gears have had time to properly mesh, it will be fine to drive as normal. You will also notice some fine metal shavings and very dirty gear oil at your 500 mile oil change. This is normal and you should be good to go until the next oil change.