I’m on my long drive home with new gears.

I’ve never understood the need for breaking properly set gears in. Do stock Jeeps come pre-broken in off the factory assembly line?
 
Sharkey said:
I’ve never understood the need for breaking properly set gears in. Do stock Jeeps come pre-broken in off the factory assembly line?
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Yeah, they have Ferris Buehler drive them all in reverse before they drop them off.
 
Sharkey said:
I’ve never understood the need for breaking properly set gears in. Do stock Jeeps come pre-broken in off the factory assembly line?
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This thread reminds me of how they talked about breaking in a motorcycle engine or a rifle barrel. It feels good doing it but really there is no proof it makes any difference. I really have not seen a side by side test of the long term results of "break in" procedures.

When I changed my fluids again at 3,000 miles and then again at 10,000 miles I saw absolutely no sign of any damage to my gears. So not sure if my gears will explode unexpectedly sometime down the road since I did not conduct any break in? :thinking:
 
What I was taught and it does make sense to me(not saying I'm right): When new gears are set up, the ring and pinion have to 'learn' each other. Every single gear setup is different from another. There are manufacturing high/low spots, the backlash specification is a range, it is not a single #, pinion depth is rarely the same depending on the tech, so when gears mesh, they develop a pattern. This is why if you remove gears later to make repairs, it is near impossible to get them back in the same position and can result in noise after repairs if the gears are re-used. We're talking thousands of an inch here.

So, if your gears are overheated or overloaded (usually due to high speed or heat/towing) they can be damaged during the initial time that the gears are 'learning' each other and will likely stay that way forever. I really do feel/think that some of the break-in procedures are excessive and overkill, but so are a lot of procedures in life because people are stupid and manufacturers want to avoid liability.

As far as new gears from factory, I do not think they are broken in, but I am not for sure. However, most factory vehicles are driven off the lot moderately. Whereas with aftermarket gears, the 2 typical reasons people re-gear are bigger tires (vehicle is being used recreationally), and performance/racing (mustangs/camaros/mopar). Aftermarket gears are almost always going to be used more aggressively.

My :twocents: : If you value your vehicle and have just spent money on a re-gear, take it easy and don't be a jackass.
 
WJCO said:
So, if your gears are overheated or overloaded (usually due to high speed or heat/towing) they can be damaged during the initial time that the gears are 'learning' each other and will likely stay that way forever. I really do feel/think that some of the break-in procedures are excessive and overkill, but so are a lot of procedures in life because people are stupid and manufacturers want to avoid liability.
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This, I know my fair share of idiots who re-gear their jeeps and while still at the shop,the first words that come out of their mouths is I'm heading wheeling tomorrow to bang on these. Keep in mind that back in Puerto Rico we were basically mudding so this means lots of spin on mud and all of a sudden you find traction, add this to Dana 30's with 37's and 5.13's and you do see a lot of broken gears.
 
Sharkey said:
I’ve never understood the need for breaking properly set gears in. Do stock Jeeps come pre-broken in off the factory assembly line?
Click to expand...

I ran that same question by the shop, with the same new-car analogy. After some back and forth, I figured that it wasn’t horribly inconvenient to do as they asked, and THEY are the ones guaranteeing their work, so I could at least do my part. Those half hour breaks gave me time to catch up on some overdue phone calls.
 
^^ Don't get me wrong...I'd do the same thing. I've just always wondered if that made me smart, or a lemming. To date, I've never had anyone provide a sufficient argument as to why you don't have to break in factory vehicles. I do know that Jeep does not recommend towing during the first 500 miles (or at least that is what the manual said on my '09). Perhaps that is because of some break in period on the gears.
 
Sharkey said:
^^ Don't get me wrong...I'd do the same thing. I've just always wondered if that made me smart, or a lemming. To date, I've never had anyone provide a sufficient argument as to why you don't have to break in factory vehicles. I do know that Jeep does not recommend towing during the first 500 miles (or at least that is what the manual said on my '09). Perhaps that is because of some break in period on the gears.
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Gears from the factory are lapped in order to get rid of some of those high and low spots as mentioned by WJ however that's still without driving load so they still need a little bit of break in period but mostly just before towing. Typically when you buy a new car you should take it easy on the engine and transmission for the first 500 miles anyway so the gears are broken in at that point. So yes they still need a little bit of break in but not as much as a brand new set and most of it is done during the time you "should" be taking it easy on the engine and trans anyways.

This info is all according to my Yukon manual that was with my new 4.88s I just got installed

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