Gear Break-in: Front vs. Rear

[lBasket]

Doing some reading on the gear break-in. I have Yukon gears, here is their page explaining break-in:

https://www.yukongear.com/blogs/the...ide-ensuring-peak-performance-and-longevity_1

According to them, proper gear break-in is extremely important to keep your gears in good condition, and maintain the warranty. I'm not doubting this. But, why does it seem like this isn't necessary for the front axle? I am not finding anyone suggesting, for example, to pull the rear driveshaft and run in 4-Hi and run the same break-in procedure a second time for your front axle. I also don't see any mention of running the break-in procedure in 4wd, and you'd think Yukon is assuming you're doing both axles.

For someone paying a shop I suppose it's different, they aren't going to do one axle at a time. I am, however. I am only one guy after all. Surely that isn't that uncommon for DIYers, I could throw the front axle in and pull the rear driveshaft and do 500mi before pulling the rear axle but that doesn't seem necessary?

Why is this the case? If proper break-in makes your gears stronger, why wouldn't you need/want to do this to the front gearset too? Sure you don't use it on the highway, but strength is important off-road too.

 

[macleanflood]

I think you're right...I think that Yukon doesn't want to deal with the complexities of explaining every scenario of having to accomplish that task with vehicles with and without locking hubs.

-Mac

 

[OldBuzzard]

I wondered the same thing when I was breaking mine in, but never got an answer. I hope you do.

I saw the weather report on the temperatures in your neighborhood. How low did it drop where you are?

 

[lBasket]

I think you're right...I think that Yukon doesn't want to deal with the complexities of explaining every scenario of having to accomplish that task with vehicles with and without locking hubs.

-Mac

True, it feels strange they don't at all mention 4wd in any way. And the way they explain not to do any hard acceleration to me makes it sound like the way the front axle more so "coasts" in 2hi wouldn't really effect the gears in the way way... but what do I know.

I wondered the same thing when I was breaking mine in, but never got an answer. I hope you do.

I saw the weather report on the temperatures in your neighborhood. How low did it drop where you are?

Fingers crossed! Or at least a "don't worry about it" from someone that knows better, haha.

The coldest I saw was -7º (house thermometer not weather app) on Monday morning. So maybe a little chillier overnight, I didn't do much outside that day but take the dog out LOL.

 

[OldBuzzard]

News said -34° near Lake George. I thought you might have got in on some of that. We had -3° in Englewood.

 

[lBasket]

News said -34° near Lake George. I thought you might have got in on some of that. We had -3° in Englewood.

That's crazy... Nowhere near that by me. I think I saw it was supposed to go to like -15 overnight, my temps are honestly closer to what happens in the metro area vs. areas like Fairplay (and maybe Lake George) It's relatively warm here for the altitude I think. Even though lake George is only like 20-30mins away lol

 

[Rickyd]

The front axle sees half the torque of the rear most of the time since it is split between both axles. It also doesn't see high speed,high temp situations that the rear does. If you set it up right it will eventually get broke in gently. You could go find some snow or sand and do some long 4hi easy trail runs if you wanted to expedite the process

 

[lBasket]

The front axle sees half the torque of the rear most of the time since it is split between both axles. It also doesn't see high speed,high temp situations that the rear does. If you set it up right it will eventually get broke in gently. You could go find some snow or sand and do some long 4hi easy trail runs if you wanted to expedite the process

I suppose that makes sense, especially with the load being split.

Technically I do intend to do the first 100mi breakin period in my neighborhood on dirt roads. Think I might as well do that in 4wd?

 

[gasiorv]

As said the front doesn't seem the loads and the heat the rear does. I just installed a new front Currie axle from Carbon and in the paperwork it said that the break in oil and the break in process does not apply to front axles. See pic of paperwork that came with axle. Funny thing is that they still shipped break in oil with the axle .

 

[Apparition]

As said the front doesn't seem the loads and the heat the rear does. I just installed a new front Currie axle from Carbon and in the paperwork it said that the break in oil and the break in process does not apply to front axles. See pic of paperwork that came with axle. Funny thing is that they still shipped break in oil with the axle .

View attachment 587370

I'd still want to change the oil at some point just to check and make sure there isn't anything abnormal going on.

That Currie/Torco stuff isn't all that cheap either.

 

[gasiorv]

Yeah, since my jeep is primarily a trail rig it will get oil changed and inspected after the first few wheeling trips. Then at least annually after that, especially since it is under water a good bit.

 

[macleanflood]

I'd be installing a snorkel if you insist on parking there...and maybe run the axle vents up with it. =)

-Mac

 

[NskLJ]

That's crazy... Nowhere near that by me. I think I saw it was supposed to go to like -15 overnight, my temps are honestly closer to what happens in the metro area vs. areas like Fairplay (and maybe Lake George) It's relatively warm here for the altitude I think. Even though lake George is only like 20-30mins away lol

We had -14 here in Woodland

 

[lBasket]

As said the front doesn't seem the loads and the heat the rear does. I just installed a new front Currie axle from Carbon and in the paperwork it said that the break in oil and the break in process does not apply to front axles. See pic of paperwork that came with axle. Funny thing is that they still shipped break in oil with the axle .

View attachment 587370

Nice! Thanks Victor, good to see it explicitly written by a vendor somewhere. Feeling better about that now.

I'll probably still do conventional in the front and change it after 500mi with the rear, definitely can't hurt and gear oil is pretty cheap.

 

[lBasket]

We had -14 here in Woodland

Overnight or during the day?

 

[hear]

I'd be installing a snorkel if you insist on parking there...and maybe run the axle vents up with it. =)

-Mac

I'd install a pump with a gear oil reservoir and a filter setup if I was going to park there on the regs.

 

[macleanflood]

I'd install a pump with a gear oil reservoir and a filter setup if I was going to park there on the regs.

Heck you do that you might as well run it through a cooler and fan. =) And throw in a couple of temperature sensors.

I'd love to know the temperature of my rear differential.

-Mac

 

[gasiorv]

Both my axles vent up at the top of the radiator and my transfer and transmission vent above the battery. It is a good easy mod to do if you do any wheeling in mud or run trails that have creek crossings. I hate mud and water, but if you want to wheel in the South East, even on the driest seasons, you got to deal with it. I am sure that is probably the same in the PNW.

 

[macleanflood]

I ran mine up next to the brake booster. Rear is tucked above the fill neck.

-Mac

 

[hosejockey61]

The front axle sees half the torque of the rear most of the time since it is split between both axles.

Only when in 4wd. Most people never use it the high majority of the time.

When it comes to great break in, they need to cycle on the pattern where the become work hardened. Remember, there is a phosphate coating that wears off during break in. The temperatures get very high during this process. If you don't believe me, try holding your hand on the pumpkin immediately following your first break in cycle. You might be able to hold it the for one or two seconds. It's slightly cooler the second time. After the break in process is complete, do it again and you'll find that you can hold your hand there no problem I'm most cases.

Breaking in the front gears has differing opinions. In general, the will passively break in and most people would never know the difference since they rarely get used. If you wanted to do it and apply the same concept to the rear, then drop the rear dive shaft and go on a drive in 4 high. I've done that and it made me feel better but I can't say that it mattered because I've also installed a front R&P and the break in period was on a tough trail. Thinking about it now, I did have a front R&P failure on a different trail but I can't attribute it to the break in process. Who knows.

I had an extensive talk with Matt at Revolution Gear and Axle about the break in process as I was getting ready to make a video on it. A lot of good conversation.

With all that being said, my advice is to follow the manufacturers recommendation for break in. You CAN tell a gear set that hasn't been broken in properly. The heat generated is the issue. That's why everything is a gentle drive the first two cycles with no towing.

Here's the video I made for the gear break in process.