Wheel Bearing Question

2010 Tacoma, 111K miles - bought new in 2010. Did my first real repair today, left front wheel bearing.
Put in a hub/bearing assembly from 05Taco4x4.

When I took off the original axle nut, I just put my electric impact wrench on it and it zipped right off. Wasn't expecting it to do anything. There was a few small areas of light surface rust inside the spindle where the bearing fits. Sure seems like the axle nut was not properly torqued at the factory. After I torqued down the new one, I put the impact wrench on it just to see, and it did not budge.

So, anybody seen this? Would it be a good idea to check the other side? Probably yes, huh. Just wondering. I've been driving near 60 years. Never had a wheel bearing go bad before.

 

I wouldn’t worry about it. There’s a cotter pin that keeps the nut from backing off.

 

When I did mine, both axle nuts seemed loose. I borrowed a 3/4 in breaker bar expecting a fight and it seemed like the weight of the breaker bar was enough to loosen the nut.

 

It would be prudent to at least check the torque on the opposite side... with a torque wrench, in the tightening direction. If it turns before the wrench clicks, this might signal that this bearing is also worn. Perhaps still serviceable, but if the nut moves significantly, I would definitely replace the hub. It is generally recommended to replace both wheel bearings at the same time anyway. But at a minimum, the axle nuts should be properly torqued.

My understanding of the hub design is that it sandwiches two opposing bearings by axial tension of the outer CV shaft, set by the axle nut torque. As the bearings wear out, the shaft tension (i.e., the apparent axle nut torque) will decrease. So it is not surprising that a worn-out bearing's axle nut would seem inadequately torqued -- not because of improper installation, but due to the wear. This is likely why your axle nut seemed loose. And also one of the reasons there is a pinned clamp over the nut.

Also, since you mentioned that you checked the tightness of the freshly installed nut by "[putting] the impact wrench on just to see," I would recommend re-torqueing it to spec, if you haven't already. Ensuring proper torque should be the final thing you do to the axle nut, before pinning it. And I use blue loctite on mine, for what that's worth -- the cotter pin thing doesn't keep the nut from coming loose, it just keeps the wheel from coming off.

 

how does a 1/8” cotter pin keep the wheel from coming off?

 

It keeps the nut from backing off. No nut falling off, no wheel falling off.

 

Thats a stretch. @6 gearT444E previously said it kept the nut from coming off. And if the nut doesn't come off, the wheel doesn't come off

 

If it was me, I'd do the other side anyway. Bearings are good to do symmetrically in pairs. If one side failed, the other isn't likely too far behind it.

 

yeah, appreciate the replies. But, I would be surprised if the bearing wore out in 111k miles. Not properly torqued, as I understand, would not put the right load on it, also maybe seals wouldn't be as effective, leading to premature wear. 300k, I would get it. I do see how a worn bearing would result in a 'loose' axle nut, but I also see how a loose nut could lead to premature bearing wear. Was just curious of others' experiences with this. Anyway, all good now.

 

Our 2006 went through a set of front wheel bearings at 92k. Not uncommon if you search around the forum here. Granted...the 2006 led a hard life before us by the looks of it at time of purchase in 2012 but my wife wanted a Speedway Blue DCSB and we got a great deal on it. Didn't take much more than a little TLC to make it all right again. The 2nd set of front bearings still spins smoothly and without play at 232k but most of those have been highway miles.

And yup, I did both bearings at the same time.

 

As @Knudsen and @fatfurious2 indicated, the cotter pin only keeps the nut from backing off the axle spindle entirely. It secures a stamped-steel retainer that engages the nut with a 12-point socket geometry, which with eight pin-engagement notches thus offers indexing options within 7.5 degrees of the nut alignment, which is within the tolerance of the part's engagement of the nut and pin. Thus unlike the typical castle-nut cotter-pin retention scheme such as on tie rod ends, there is no need to ever tighten the nut beyond its torque spec to allow installation of the pin, as the retainer can be installed and secured to accommodate any orientation of the nut. However, the retainer doesn't ensure that the nut applies proper axial loading of the bearings, which is why it is crucial to properly torque the nut before installing the retainer.

As you questioned, the cotter pin doesn't directly provide the axial retention forces necessary to keep the wheel affixed to the truck. It simply keeps the nut from spinning off the axle. The nut provides the positive retention of the wheel.

I happen to be disassembling my truck at the moment, so I can provide a picture:



Actually, I had already removed the nut and its retainer, before I decided to go back and take the picture. I have honestly been confused why you asked this question, but I figured I'd give it my best shot. In this picture, the nut is only finger-tight. But if I re-bent the cotter pin, then the nut couldn't spin off the axle, and I could probably drive the truck like this for a while before the wheel came off, even though that would be a very bad idea because the axle nut is only finger-tight.

This is why I was recommending that OP torque the axle nuts to spec, instead of relying on the cotter pin retainer to keep the wheel on. Both on OP's new hub, in case OP might have inadvertently loosened it by testing its 'snugness' with an impact. And also on the opposite hub, which might be considerably worn, and thus lack proper axial loading of the bearings. (I.e., of that nut tightens prior to torque spec, this would likely indicate need for bearing replacement in the future.) Even though the cotter pins would keep the nuts from backing off entirely, and thus keep the wheels from literally falling off.

I feel stupid writing this all out, but I happened to be in a position to support it with a nice picture. @6 gearT444E your contributions to this forum have been prolific, and overwhelmingly helpful to me in countless instances. I'm not sure why you called me out here -- if I was offering bad advice, please correct me for everyone's benefit.

Or were you just trolling me? If so, let me call you out on your obvious bullshit. No way that little cotter pin is actually 1/8"... these trucks are metric, right?



Dammit, you win again!

I'll get you next time, @6 gearT444E !!!!

I have only been driving for ~30 years, much less than your ~60. But in my experience, having a bearing wear out after 100k+ miles is entirely normal. My Tacoma had a bad bearing at 180k miles, but I don't know if that was even the original hub. In fact, of the vehicles I've owned, while in my possession, all have had bearings go out within 120k miles of ownership. That's ... like 8 cars of domestic and Japanese manufacture... and I regret to say the longest-lived bearing was a Ford I bought new, at 120k. Perhaps my Tacoma made it all the way to 180k on its factory bearings, but I bought it at 170k so I don't know. Maybe I'm just a terrible driver?

Perhaps your axle nut was in fact undertorqued from the factory, leading to premature failure. Entirely plausible, and most unfortunate.

But in my opinion, it is totally normal for a bearing to wear out after 100k+ miles, and as a result, for the axle nut to seem loose. Without a time machine, we'll never know, and out of warranty, it doesn't really matter. The important thing is you identified the problem and fixed it.

 

Right I get that, but originally stated "the cotter pin thing doesn't keep the nut from coming loose, it just keeps the wheel from coming off"

That's certainly a very thorough explanation and I appreciate the pictures! I did not think my statement was there to cause any offense, just a little inaccurate IMO. "the cotter pin thing doesn't keep the nut from coming loose, it just keeps the wheel from coming off" In my mind the cotter pin keeps the nut from backing off which in turn keeps the hub from falling apart due to loss of axial load or totally coming off the spindle (not sure if the nut could totally back off the axle threads with the dust cap on?). Sorta like the skeleton dance song I suppose.


No trolling intended, just maybe was thinking your initial statement made a little leap there. And the 1/8" was just a guess but glad my calibrated eye is still on after all these years

And my taco I had the passenger front wheel bearing go out within 40k miles, I did both side fronts at the same time. The back ones lasted until 60k in which I believe the seal leaked causing gear oil to wipe the bearings. Much of my bearing degradation was probably due to larger tires and taking the truck for a swim offroad.

My 2014 accord has the original front bearings at 210k! They are not unit hubs though, so maybe that has something to do with it? The honda rear unit hubs went bad at 120k.

 

My wife's Civic made it to 110k on factory hubs, and only to 170k before the head gasket blew. Bone stock and well maintained, so that was kind of disappointing. But how cruel the irony that our Ford made it slightly further on its stock hubs? We're banking on its engine holding together a bit longer as well, hopefully. Yikes to that reality.

The Tacoma eats bearings and CV axles for lunch, though, what with its oversized tires, and an ongoing problem I've tracked down to somewhere between the seat and the steering wheel.

I will concede as to the inaccuracies of my initial claim, backpedal my speculative accusations of trolling, and reiterate my thanks for your countless helpful posts over the years. And I'll die on that hill!

 

It's a cone style bearing if memory serves so yes, as it wears, it will lose preload (torque). My.drivers side went to 107K and at 112K (last oil change)the passenger side isn't showing any signs of wear (play) but I have the spare on the shelf and it only takes about 30-45 minutes (including beer) to swap out if you have tools gathered and ready.

I honestly figured the passenger side on mine would go first so I may go ahead and swap it out next weekend or two just for peace of mind and at recommendations I have gathered from here.

Glad we have such a large knowledge base developed here over the years to get feedback from! Tacomaworld has helped me immensely over the last 14 years of ownership.

 

I think the quoted member’s intent was to say, “the cotter pin doesn’t just keep the nut from coming loose, it also keeps the wheel from coming off.” As in, retention of the wheel is the ultimate reason for the nut to be pinned.

 

If you've ever exchanged wheel bearings on a 1st gen Tacoma, the 2nd gens almost change themselves!

 

Mine zipped right off as well with my 1/2" Milwaukee stubby impact, replaced both side fronts at 180k as a precaution before a road trip, no noticeable difference before/after but I assume they had to have been worn since the previous owners maintenance records never mentioned them.

FWIW I've always had drivers side bearings wear out first (4 separate vehicles, combination of both fronts and rears). Supposedly this is due to the crown on the road, they're pitched to shed water to the sides so theoretically you have slightly higher forces on the drivers side bearings. Whether I replace both sides depends on how easy they are to do or how motivated I feel lol. These fronts are so easy and came in pairs from 05Taco4x4 so I did both.

I've had a rear bearing go on a subaru at 130k, the fronts lasted another 50k, and the last rear was still going strong at 235k when I sold it, so YMMV but sometimes its worth leaving it until you hear it

 

Bearings in general perform best and last longest when the load is perfectly radial. I can see how a road crown places the bearing slightly away from parallel with gravity, introducing a load vector that’s not perfectly radial and therefore reduces the bearing life…

 

When a wheel bearing starts to go bad, it will start to humm and possibly put off some vibes (both of which I am currently experiencing). Is this something that needs replacing ASAP or can you drive on a bad wheel bearing for a while without much concern? Will it damage anything else if left too long??

 

I wouldn’t drive on it more than say a few hundred more miles. It can cause premature wear or damage to suspension parts connected to that wheel, and can also eventually become a safety concern.