Just geared to 5.29, dumb question

To my fellow Tundra owners who have upgraded gears…

I’ve searched and can’t really find a definitive answer, the Yukon site really doesn’t say, and the shop that did my gears didn’t cover this when explaining the break-in procedure.

Am I assuming correctly that when in 2WD, the front ring and pinion do not spin, and therefore, I must engage 4WD and follow the standard 500-mile break-in procedure as well for the front gears?

If so, I’ll of course do it to protect my investment, but damn, that’ll take a long since ostensibly I can’t drive it on the pavement!

Thoughts are appreciated!! Thanks!!

 

The front diff isn’t the power diff. It’s not as critical on the heat cycles like the rear. The rear is used for everything and needs to be heat cycled properly. The front just needs to be used when needed.

 

You’ll be fine, next time you do gears get them polished and then no need to worry about break in

 

Yes, break them in easy on the dirt.

 

This makes sense, I’m hoping that’s what my shop will tell me too. Thank you!!

Yeah I wanted to order the Nitro gears from SDHQ as polished, but the shop I’m using exclusively uses Yukons, and they didn’t offer polishing. Not a lot of really reputable, technically proficient 4x4 shops in my neck of the woods. The one I use is probably amateurish compared to the ones out West.

 

It’s definitely hit or miss across the board of who will install customer supplied parts and who will do full install or only diffs. I wanted mine polished and I didn’t want to pay to have someone else install them after being built. I shipped mine out for polish and found spare/donor diffs to keep the truck on the road.

 

Yukon is quality stuff. Run them in my rock crawler. I’ve got unpolished nitros in my tundra and no issues after 7-8k miles and I towed my sxs after about 350-400 miles of break in.

 

The front diff still spins, even when in RWD.

 

THANK YOU! Once I read this, I did even more searching, and read that indeed, when in 2WD, the CV’s (of course!), ring, pinion, and front drive shaft still spin, just not under torque, and possibly not at the exact same speed as the rear drive staff and components (though close). Because it’s all spinning, that allows you to engage 4WD “on the fly”; the transfer case locks the front and rear drive shafts together with torque split 50/50, and the shafts now run at the exact same speed, unless there’s a center differential in the transfer case, in which case they can sometimes spin at different speeds, which now makes sense as to why I can drive my Sequoia on pavement in 4WD! DUH!

So in a nutshell, the front ring and pinion are heat cycling even in 2WD, just possibly not to the extent of the rear since there is no torque. But, since 4WD is used a lot less, probably not as critical.

Thanks to everyone for contributing!

 

Actually the front diff doesn't spin in 2wd. This video explains why. While parked in 2wd, you can freely rotate the front DS as it's disengaged at the TC as well. Definitely makes greasing the U-joints a breeze.


Edit: I too have 5.29s. For piece of mind about breaking in the front R&P, I hit some dirt roads in 4hi. Probably unnecessary since it's not an axle that sees a lot of load, but I felt better about it

 

Now you can see why I asked the question, lots of differing views out there on how our systems work, some say they spin in 2WD, some say they don’t…THANK YOU for sharing the video!!

 

In that video you posted, the guy spins the left CV axle, and it turns the gears in the diff. The diff may be disconnected from the driveshaft, but the gears in the diff spin as the wheel on the side that stays connected (the left side) spins.

 

Just some food for thought. The break in period is not needed, theres not a single new car bought that has ever had the gear oil change done @ 500 miles, or any other amount of miles.

 

You know I don’t disagree but aftermarket gears I just don’t trust to have the same build quality as oem. And for the $5500 I spent, I’ll drive nice for a few hundred miles.

 

Yes but it’s not under any real load as there’s no power being sent to it. Reminds me that I need to change my front diff fluid. Only got 7-8k on it since the fluid change.

 

My gear builder explained to me that manufactures use a very simple polishing process, and that’s why there is no break in period. Aftermarket gears are untouched when they get shipped out

 

I can tell you I’ve regeared hundreds of 7.5” clams, 8” clams, and 9” clams, and they don’t spin in 2wd. Don’t believe me, go zip tie your driveshaft to the frame. If it breaks in 2wd, then you’re special.

 

Think that thought all the way through. If that were the case then for the first 500 miles you're polishing/smoothing the gear surface. If thats true then you've just changed the backlash and would need to redo it. If it were important.

This comes from a guy who's done hundreds of R/P's on everything from ATV's to earth moving equipment.

 

Yes but those are the SIDE gears that are spinning, not the main ring and pinion, so in 2WD, with the front ring and pinion not spinning, they aren’t getting the break-in workout like the rear ring and pinion. When 4WD is engaged, the transfer case starts the front prop shaft moving, thus moving the ring and pinion, and at the same time, the ADD engages which essentially is an automatic locking hub. Ergo, if you want to be OCD like me , you must engage 4WD if you want to do a proper 500-mile break-in like the rear. HOWEVER, general consensus seems to be the front gears really don’t need as extensive of a break-in as the rear.

Thanks again to everyone, this has been an AWESOME learning experience!! That video @PolishedTRD linked is fantastic; HIGHLY recommend anyone watch it who wants to geek out on the inner workings of our 4WD system!!

Here is another one I found interesting, shows the guts of a diff, and interestingly to this thread, shows how, in 2WD, the disengaged front ring doesn’t move but the side gears still move the CV’s and thus the wheels (passively) at the 3:25 mark.

https://youtu.be/e-VvLw7pjk0?feature=shared

 

That’s why I had mine polished professionally prior to install

Have you heard of Zuk? That’s who I got my info from.

 

That’s basically what a break in period is, no? Polishing and smoothing. You can’t put two pieces of metal together in that situation and not have some kind of wear occur. I’ve never installed but I’ve seen new r/p’s and r/p’s after a few hundred miles and there is a very noticeable difference in the faces of the gears and also a big change in heat in the diff.

 

First, congrats on choosing to regear. That’s a big financial commitment, but so worth it. You’re gonna love it.

Second, I agree with the others that have suggested finding a dirt back road and putting in a little rally session. It’ll at least knock the coating off the gears and you can flush that out and put in clean oil. Otherwise, nothing to worry about.

Third, Yukon is fine stuff. We’ve ran it for years in our wheelers and race trucks.

But, when did Yukon start making gears for our 2.5 gen Tundras? Thought we were limited to Sierra or Nitro. I’ve got Nitro gears in mine with about 70K miles on them. Lots of towing, and they’re still great.

 

Thanks for the feedback Chad! Not sure when Yukon started making them for the 2.5 gen.

 

It does shine them up, its metal on metal, thats what it does.
What it doesn't do is remove so much metal that you'd need to change the gear oil

 

No, I haven't but that doesn't mean anything, theres thousands of guys that do gears.

 

Check him out, he’s got some nice builds
http://www.gearinstalls.com/

 

So what’s all those small metal flakes and sludge that’s on the magnet when I do an oil change after a few hundred miles on new gears? Added friction modifier?

 

Zuk is the man, he did my LSD and elocker. You just have to be local to Prescott and have cash $.