front differential side bearing replacement.. done!

What is the cause. Is it just a maintenance item to be expected after so many miles because you can't grease them like in the old days or is it from off roading in deep water a lot ?

 

Nobody seems to know for sure. It seems like the consensus is that it's under-designed for the loads that it is subjected to and there may be an incompatibility/inconsistency between the hardness of the materials used in the manufacture of the bearing and the axle causing accelerated wear. Most people seem to experience the problem immediately after doing a lift. Whether or not the lift causes the problem or simply reveals a problem that was pre-existing is unknown and so far open to speculation.

One thing I wonder about is how many people who experience this problem attempted to drive around cornerns in 4wd on dry pavement at one time or another. I know I did it a long time ago when my truck was new before I knew better...


EDIT: go back and read Crom's post -- post #90 in this thread

 

So you are replacing your axle with a used part? Hmm, seems kinda like a crapshoot to me. Do you know how much a new axle costs?

 

I am not sure if this bearing is the problem with mine, or if it's just the wheel bearing / axle. After I change the bearing / axle, if it still makes the noise, I guess then I'll know for sure. I have been lifted for over 60,000 miles now. I have 90,000 miles on it. I remember when I first lifted it, people telling me the axles would wear out in no time at all. I do not think that is the case. Yes, it may cause them to wear sooner than they should have, but I have wheeled it for the last 3-4 years and I have never had anything break. I do know the boot on the drivers side axle has been leaking grease for a few months now. That is the only reason I am replacing the axle. The wheel bearing I know needs replaced, but the axle does not click or anything. I just figured since I'll have it all apart, I'd replace it and see about rebuilding it for a spare. It would make a great spare since it fits both sides. It may not be bad, and just need a new boot. Guess I'll find out soon.

 

Thanks for the reply BenWa. Maybe the lift puts extra pressure because of a different angle then OEM. How R U doing with the beads or is that a private matter ? Thanks again for the information.

 

New in some cases was the same price or less than remanufactured axles. Yeah, I was concerned about going reman, but the TW guys in my area say they're just as good (boots are certainly better than stock). And since I couldn't find a new one without waiting forever, I'll give it a try. Shoot, even the parts guys at the dealership told me to go this route when I asked them what a factory one cost (around $400). And it is just preventative in case the bearing has scored the axle (which may be my problem from the last diff).

 

Think I found this site which has some cheap prices for parts:
www.toyotapartseast.com

 

Okay, so much for a pictured writeup (I know, epic fail on that part). We were just too busy working on it (took about 4 1/2 hours using hand tools, working out of a box of loose tools on mod day). You cannot do this without two people! But I also learned a lot from the worn parts.

What's the hardest part? For us (I say us because 06RadiantRed helped me out all the way), it was getting the CV Axle out. What will be the hardest part for most people? Getting the CV Axle out AND getting the bearing out. 06RadiantRed's adapter worked perfectly. I attempted to make an adapter out of thick washers (pics below too) but I only used one washer. Since the bearing was in there really good, the washer eventually bent over (sending me flying on my butt). I had played around with stacking washers and I think we're in a consensus that it would have worked because it would have prevented the large washer from bending.

What to take apart? Everything you would do to remove the shock (and remove it too). Completely remove the sway bar from the whole truck to allow yourself enough room. We left it attached only on the passenger suspension and it was still in the way. So it should be completely removed! Once you've undone the LCA bolts (actually loosen the axle nut before removing these), sway bar, and removed the shock, you're ready for the axle nut to be completely removed. Swing the whole unit off and forward then pop the axle from the front diff.

The washer above the tape is the one I made to pull out the bearing. The washer must be thick and larger than 1.5 inches. Then I took a dremel and ground it down to the outer size of the bearing (eyeballed it). I also cut off two sides. Because the bearing is up against the teeth behind it in the diff, we had to do a little more dremel work to round off the corners on one side to help stand it up in the groove behind the bearing. I had rented a slide hammer and a pilot bearing removal tool which I then expanded inside the washer. That part worked fine (until the washer bent) and no needles ever came out. I considered stuffing a piece of a sponge in there just in case, but didn't really see the need.


So I think if I'd stacked these other washers behind it, it would have been thick enough to keep from bending. With 06RadiantRed's adapter, we just didn't fuss with it anymore and used his adapter.


On installation, you will need some things in advance. You'll need a large washer (again, one just larger than 1.5 inches works), a decent size socket, and some extensions (at least a foot combined). One person holds the bearing in place with the washer on the outside of it while laying under the truck. The other person takes the extensions with socket on the end, places the socket against the washer and then hits the end of the extensions with a hammer to drive the bearing in. It's a little tough to get it started, but it will go. After a few taps, keep checking it to make sure it's straight. And keep that washer on there flat so the edge of the bearing doesn't bend. We tapped it in until the washer sat flush with the opening where the bearing resides. You'll see those edges are tapered and the original location was in another 1/8 inch. I don't think the difference will matter any because there is a ton of room on the axle where the bearing rests.

To install the new seal, we purchased a 2-foot piece of 2 inch PVC pipe and a fitting. The fitting fits absolutely perfectly on the seal to pound it back in!


It will be very helpful if you have a 3rd person to hold the disc/brake unit forward away from where you need to work while also making sure the brake lines are not stretched.

And now for the carnage pics and my thoughts on the damage/wear.

So this is where the bearing rests on the axle.


And this is where it now rests leaving it out a hair:


So not much difference. But take a closer look at the axle:


How about a closer look?


First, I want to say that the area where the bearing sits is worn down (thus, a loose fitting when it's in the truck). That would be over 100K miles of the bearing wearing down the axle. I can feel the rise from the worn area to the non worn area (and I think I can see it visually too).

What are those other marks there? Those are deep scratches in the axle from the individual needle rollers. They do not extend all the way around, but only cover about an inch of the circumference. So at some point, the needles were gouging back and forth on the axle!

Here's my guess on that. I spend a lot of time on forest roads (bumpy). And whenever I'm on those roads I put it in 4wd for 3 reasons: 1. We're supposed to do so for about 10 miles per month. What better time than this? 2. Better traction in the loose gravel/dirt especially on the hills. 3. This is the most important to this result, I think. I always figured it was easier on the bearing if it were turning with the axle (needles not being used) rather than having the axle turning inside the bearing when offroad. I thought it would put less stress on it that way. The evidence says otherwise. The only way those gouges can happen is if the needle is sitting in one spot on the axle while the suspension is traveling up and down.

So it seems there's a design problem. Driving it in 4wd offroad is evidently the cause of the front diff bearing problems (in my case anyway). My lesson learned is to keep it in 2wd offroad if at all possible. Seems kind of backasswards to have a 4wd truck that should be kept in 2wd offroad, but the evidence speaks for itself.

And now I can drive around all I want and enjoy the smooth feeling of the road without any vibes/rumble!

 

+ rep, Moose. Bummer that you weren't able to get more pics of the process but I think your write up is pretty clear and descriptive anyway.

Did you measure the difference in axle diameter with a micrometer or anything to see exactly how much wear there was?

I somehow am having such a difficult time buying that. But maybe it's just because I don't want to buy it. If you are right about this, I guess it proves the theory about the incompatible brinell hardness between the needles and the axle. Just have such a hard time swallowing the idea of routine offroad driving in 4wd having such an adverse consequence.

Awesome! Well done guys!

 

Same here. Considering the amount of time my truck spends in 4wd I would think I should have problem with needle bearings long time ago. So far knock on the wood my CV is still tight and almost no play in it. I also dont think there is posibility to make notches like that with out extra factors.
1. Not enough diff oil
2. CV needs to run being out of alignment (wheel bearing destroyed or installed incorrectly)


Moose how you fill front diff? Do you add oil until drips out of fill hole?

 

Just finished repacking the new bearings. Noticed that I got one Koyo and one NSK from napa. We'll see if there is a different failer point for each brand. Teardown starts tomorrow early morning.

 

Ben and Blue, yeah it just doesn't seem to make sense. I did not measure the wear area but you can definitely feel it (and I had to turn in the axle today to get my core refund). Again though, I wish I knew if the first diff caused those gouges. I don't think the wear on the axle means anything in relation to the vibes because that wear was probably there last year when I got the new differential and the vibes went away completely. They didn't reappear until I removed the diff drop (and then got worse when I raised it back up from .85 to 1.75 on the 5100s). So at stock angles, the wear made no difference. So it couldn't have caused the vibe (in my case anyway).

But the vibe has been slowly getting worse. When did the scratches/gouges occur? Years ago? In the last 6 months? That's really what I need to know to narrow it down. I'd like to see many others take theirs out and inspect the bearing and axle. Because the bearing looks fine in looking at it and feeling it, but then that's been the same situation for others that have replaced it. Now several did have pitting/scratches in their axles too. Maybe that's what causes us to feel a vibe? Now did the scratches/pitting (on others) get caused by a "bad" bearing or really a bad axle that isn't holding up to the bearing? Is it not getting enough oil inside that bearing? The oil has to seep in around the edge between the bearing and axle. There's not much room there. What's circulating the oil in/out of the bearing? Does the oil constantly sit in there spinning and get overheated? Is that why so many say the vibe is worse when it's cold but goes away when it's warm? Just too many variables to figure it out.

FYI, my dad was a mechanic (retired now) and I learned a long time ago to fill until it's coming out the fill hole (and I'm on a level surface in my garage when I change it). Now that's on the first diff. I hadn't changed it on the new one until yesterday because I hadn't hit 30K miles yet. Remember, this was a new front diff I got 14 months ago and the dealership installed/filled it. Based on the quantity that came out, it was not low on oil. So maybe a freak thing is happening offroad? Maybe that's why it's so random on various trucks (2 in less than 50K miles in one case when the 3rd finally worked)? You would think that if it were happening regularly, the scratches would be all the way around. But they're limited to just one section. That makes me think it happened on one trip while I was in 4wd the whole time. It seems the axle must have been rubbing really hard on them when the wheel was dropping down off of rocks. That's the only time the angle is going to be severe. I just don't know. Maybe it was a bad needle or bearing in the first diff and these were here before?

Sorry, I'm rambling on. I go down one train of thought, but then think of one of your other questions and then go down another train of thought. That's why I think there's just no easy answer due to too many variables.

 

After doing lots of research looking through the manual, forums, and physically inspecting the truck I've had my theory as to why we are having problems. It wasn't until i saw the images of the most recent post showing the score marks on the axle shaft was I fairly certain.

My truck is completely stock with the exception of the TSB leaf springs. I have never had a lift of any kind on the truck and it currently has 23k miles. The reason I feel like there was a problem in the first place was strictly by way of inspection. I have no sort of vibration or anything like that however during my normal oil changes at around 15k miles I inspected all of the drivetrain for any tears in the boots, etc. What I found was an extremely loose drivers side axle. The play in the input shaft into the diff on the drivers side was extremely excessive. I took it into the dealer and they were clueless so I have an appointment to see the toyota rep. My plan is to discuss with him everything I've found so far.

My theory is that the problem isn't with the needle bearing itself but rather with the tapered roller bearing on either side of the differential and how the diff is shimmed.

According to:
The method to assemble the front differential goes through setting the backlash of the differential and adjusting the torque value of the bolt holding the input flange and by swapping out the pinion shaft shim. The method used in the manual calls for an initial preload value for the pinion shaft and after assembling the diff with the backlash set and the differential installed that the preload should be increased by a certain amount (calculated engineering value). The problem with this method is that it isn't a really accurate way of quantifying the preload on the differential itself. I think the problem is that the differential does not have the proper preload and the two tapered roller bearings are not holding the diff in place. What is likely happening is that the differential is moving up and down as our suspension goes through its motion which explains the score marks shown here

It is amplified when you lift the truck and in fact if you lift the drivers side of the vehicle and spin the wheel, you should be able to hear the tapered roller bearing and if you push and hold the axle straight while you spin the wheel, you should notice the noise goes away.

Also, the needle roller bearing everyone seems to be concerned with. To be clear, this bearing is pressed into the differential. There are actually two of these bearings one on each side of the diff. You can see the needle roller bearing in this picture and how it is pressed in (shown to the right of the green circle).


I think that the fix to the problem is to properly shim the diff inside the differential housing. You can see one shim in the picture above. It is the one with the holes in it.

If you look on page 4 of
they call it "Case Washer". Also the needle bearing is called "Differential Side Gear Bearing"

The reason why the needle bearing is the one to go is that it is the weakest link in that interface. If the diff was shimmed properly we wouldn't be having any problems. Also, for those of us that do not have any issues, it is likely that you got lucky (maybe) and that your differential just happens to be shimmed enough to not allow for any up and down movement.

Here are some videos to further illustrate the problem shown on a rear diff:

Not enough preload:
http://youtu.be/g-RyFBZWSYM

Too much preload:
http://youtu.be/C8bLFqSdgYI

Just right:
http://youtu.be/8PgMVP596mw

Also one showing what it looks like spinning. Clearly shows how it could be possible to have those score marks on the axle shaft:
http://youtu.be/Kv13WHFTOuk

I'm willing to bet that if you slide the new bearing onto the old shaft, you'll be able to see that the score marks and or wear marks extend past the bearing width. The side to side/up and down movement of the diff are probably the cause to those score marks, vibration, and loose drive axles.

 

Also for those of you installing new needle bearings in hopes of curing the problem. Be advised that there is a specific press in depth the manual calls out.

Front differential side gear needle roller bearing
Bearing press in depth

1.4 to 2.0 mm (0.055 to 0.079 in.)

 

One problem here, you can not get those score marks on shaft that is lubricated. those score marks look like needles just fused to shaft itself which happens often where lubrication fails. Anybody who did rebuild few solid axles can tell you that there are in prints like that when all grease is out and heat fuses the rollers or the race.
Pass side always have half shaft straight through the rollers so oil can flow from one side to another easier. Driver side have CV always at slight angle so oil can not just flow as easy, and considering how little room there is for oil its amazing that any of it flows. Manual calls for 1.6 US qt of oil for front diff. I always end up putting little over 2 qt and my front diff oil was changed twice already in 40k miles because I use so much 4x4 that I dont want to keep it longer.

 

The shims have holes in them specifically for this reason. They aid in allowing for the gear oil to flow to that bearing. There may be a link to poor lubrication and this damage. What I do know is that needle roller bearings are prone to get flat spots on them if they are exposed to loads they are not designed for for example the excessive loads they see if the diff is not shimmed properly. If the needle bearing is developing flat spots on each of the rollers, it could be possible that they fuse to the shaft.

The reason I don't think this is a problem is because if you look at the fill hole, it is well above the location of the needle bearing which means its probably swimming in gear oil. That being said, if it turns out that Toyota (or whoever assembles the diffs) cannot properly shim these things I wouldn't be surprised if the bearing is indeed lacking the proper lubrication.

 

The biggest question to me here is this: has there been any failure reported due to this? I have this noise for 30K miles now, and I stopped worrying.

So:any failures at all, or not? I have not heard of even one.

 

Do you just feel the vibes at 35-40 or do you feel vibes at different speeds as well? I noticed over time that my vibes have spread to other speeds- 5-10 and 20.

 

Well ... hard to say, the main vibe is between 35-40mph. I sometimes *think* that I feel it at different speeds as well. But: most of the time others don't even feel it between 35-40 and call me nuts (there are a few with me who can feel it).
So my real question is: any failures. Or, in other words: is this really that serious? With no failures, why would you spend 5 hours replacing that gasket / seal if most likely the vibe comes back anyway? I mean, why was it there in the first place for so many? Unless you change something in the design, it ought to come back, no?

 

Instead of using the Toyota bearing made by Koyo, I may try a Timken bearing from Rock Auto and see if that one lasts.