Premature trunion bearing wear (1 Viewer)

[NielsC]

What would cause the trunion bearings from the knuckles to wear so they have a flat spot when the knuckles are in straight position?
It’s been a year and half since I’ve rebuilt my knuckles, and now I have to rebuild them again because the bearings are worn.
There’s no play on them , but with the steering linkages disconnected it feels like there’s a flat spot in them.
Preload too tight? Too loose?
I’ve always done them on feel and reused the shim that was on the trunion cap. Preload always felt good.
Now I’ve ordered a fish scale to check preload.
Also, is there any other grease to use on the trunion bearings? I’ve used wheel bearing grease as specified, but it would mix up with the moly anyways? Is it better to pack them with moly, or use another heavy duty non-moly grease in them?

 

[BILT4ME]

What would cause the trunion bearings from the knuckles to wear so they have a flat spot when the knuckles are in straight position?
It’s been a year and half since I’ve rebuilt my knuckles, and now I have to rebuild them again because the bearings are worn.
There’s no play on them , but with the steering linkages disconnected it feels like there’s a flat spot in them.
Preload too tight? Too loose?
I’ve always done them on feel and reused the shim that was on the trunion cap. Preload always felt good.
Now I’ve ordered a fish scale to check preload.
Also, is there any other grease to use on the trunion bearings? I’ve used wheel bearing grease as specified, but it would mix up with the moly anyways? Is it better to pack them with moly, or use another heavy duty non-moly grease in them?

View attachment 3219743

What brand of bearings did you install?

Did you check preload?

 

[NielsC]

What brand of bearings did you install?

Did you check preload?

I’ve used Koyo’s before and had the same problem, this time I used SKF bearings, and again the same problem after a year.

Like I said I didn’t check the preload because I did’t have a fishscale, but reused the shim that was on the top trunion pin, and it “felt” OK, no play, not too loose, not to tight.
Mind you I run 35s, and do the occasional offroad trips, so I asume those bearings sure take a beating, but I would think they would last longer.

 

[OSS]

Tight preload won’t grind a flat spot in the race. The vehicle weight is 1000X times more forceful than any preload.
My guess: QC of the metal used for the bearings and race. It simply wasn’t as strong as it’s supposed to be.

 

[BILT4ME]

I’ve used Koyo’s before and had the same problem, this time I used SKF bearings, and again the same problem after a year.

Like I said I didn’t check the preload because I did’t have a fishscale, but reused the shim that was on the top trunion pin, and it “felt” OK, no play, not too loose, not to tight.
Mind you I run 35s, and do the occasional offroad trips, so I asume those bearings sure take a beating, but I would think they would last longer.

What does the bearing rollers look like?

Mind you, these bearings only ever rotate about 15°.

Your are showing wear, but don't appear grooved. Are the rollers flat-spotted?

When I rebuilt my front axle at 196K miles, the races had serious grooved worn in them and the rollers were heavily pitted. The PO 's had never had the trunnions done in that time, soi could move the wheel just like loose wheel bearings except it was the entire knuckle.

Are the races showing even wear from the inboard side to the outboard side? If so, the the bearings are carrying the load evenly. If the inboard side of the top bearing shows much more wear, then your tolerance is too loose.

 

[jellis]

I fully redid mine with OEM equivalents including swapping shims because preload was off. Then I had to get back in there right afterwards for some reason or another. You know what? They were just like yours right away, flat sticky spots right after rebuild! If you are doing everything right, I wouldn't worry about it. I think the lack of rotation and high forces makes this inevitable, but I also think what you feel in your hands on an unweighted front end is irrelevant to weighted, on the road performance.
(Note I am taking about minor catches while rotating here, not seriously damaged bearings that are hard to turn once caught)

 

[NielsC]

Hard to tell, but the top race might have more visible wear on the inside then on the outside.
The rollers look like they have flat spots indeed.
The lower race and bearing look more or less the same.

 

[NielsC]

I fully redid mine with OEM equivalents including swapping shims because preload was off. Then I had to get back in there right afterwards for some reason or another. You know what? They were just like yours right away, flat sticky spots right after rebuild! If you are doing everything right, I wouldn't worry about it. I think the lack of rotation and high forces makes this inevitable, but I also think what you feel in your hands on an unweighted front end is irrelevant to weighted, on the road performance.
(Note I am taking about minor catches while rotating here, not seriously damaged bearings that are hard to turn once caught)

My knuckle really catched a tight spot in the straight trough position. It would really jump in to it when I rotated the knuckle past this point like it was spring loaded.
When I put the bearing back, but 90 degrees rotated, this tight spot was gone, but it would also catch minor in multiple spots.

 

[aztoyman]

Look up false brinelling or fretting of bearings.

 

[NielsC]

Look up false brinelling or fretting of bearings.

Sounds plausible… so they might have been too loose so that the rollers can rattle in the race and push the grease away?

 

[aztoyman]

We used to look at failures of parts with a microscope and had test equipment where I once worked. I was just providing food for thought based on the pics posted.

Also, you have to be careful with the pull scale measurement. It can show it's set correctly and actually be too tight. The rollers should roll smoothly. If they feel notchy they are too tight even though the scale says you are within spec. On large machinery we could actually see the rollers kind of skip or slide. We really can't see it happening on our trunnion bearings but you can feel it.

 

[-Spike-]

What would cause the trunion bearings from the knuckles to wear so they have a flat spot when the knuckles are in straight position?
It’s been a year and half since I’ve rebuilt my knuckles, and now I have to rebuild them again because the bearings are worn.
There’s no play on them , but with the steering linkages disconnected it feels like there’s a flat spot in them.
Preload too tight? Too loose?
I’ve always done them on feel and reused the shim that was on the trunion cap. Preload always felt good.
Now I’ve ordered a fish scale to check preload.
Also, is there any other grease to use on the trunion bearings? I’ve used wheel bearing grease as specified, but it would mix up with the moly anyways? Is it better to pack them with moly, or use another heavy duty non-moly grease in them?

View attachment 3219743

These bearings move back and forth constantly, over less than a degree of rotation, as you drive straight, which you do 99% of the time. The grease doesn't get redistributed unless you turn the wheel, and even then not much. Not an ideal situation for roller bearings, which are designed to be rotating, primarily in one direction, all the time. What you are seeing is normal, exacerbated by large tires and offroad use.

I personally use moly grease on everything just because non-moly doesn't offer any advantages, and with that in mind why bother with two types? But for trunnion bearings in particular, moly seems to be a better fit. That being said, it doesn't solve this problem either. They are a wear item. Most people don't notice how quickly they wear because the wear isn't obvious unless you disconnect the steering linkages and rotate the knuckle. As long as they are still tight and no play is felt when rocking the wheel at 6 and 12 while off the ground, I don't mess with them.

 

[aztoyman]

At a year and a half, I think it's too soon to be looking like that. If it were me, I'd just be more mindful of the preload setup. I'm not saying you weren't when you last set them up. But setting them up over again assuming the shim packs are good and getting the same result is getting you nowhere.

It seems they "might" be too tight. You obviously don't want them with any freeplay. There is a range of tight so to speak. It can be set with zero play and still go tighter but there will be a point where the rollers stop rolling and slide. You CAN feel it. Try it some time. And often it will read good on your pull scale.

 

[BILT4ME]

At a year and a half, I think it's too soon to be looking like that. If it were me, I'd just be more mindful of the preload setup. I'm not saying you weren't when you last set them up. But setting them up over again assuming the shim packs are good and getting the same result is getting you nowhere.

It seems they "might" be too tight. You obviously don't want them with any freeplay. There is a range of tight so to speak. It can be set with zero play and still go tighter but there will be a point where the rollers stop rolling and slide. You CAN feel it. Try it some time. And often it will read good on your pull scale.

Based on what I see, I would deem them too loose.
Looking at the shallow wear pattern on the outboard side, I would say the bearings are not evenly distributing the load.

It is also interesting when you look at different brands of bearings, the number of rollers can vary as well as the diameter of the rollers. More rollers would distribute the load between them.

I noticed this when comparing wheel bearings between Koyo, Timken, and O'Reilly's house brand Chyna ones.

 

[aztoyman]

I see the pattern you mentioned. I'd also think that loose would be felt. Good observation.

I also found Chyna bearings with not only fewer rollers but shorter. Didn't even span the entire race.

Either way I think close attention to shimming is warranted. There's a lot of other people running loaded 80's with large tires out there without short trunnion bearing life. Or is there? I don't own one.

 

[-Spike-]

I see the pattern you mentioned. I'd also think that loose would be felt. Good observation.

I also found Chyna bearings with not only fewer rollers but shorter. Didn't even span the entire race.

Either way I think close attention to shimming is warranted. There's a lot of other people running loaded 80's with large tires out there without short trunnion bearing life. Or is there? I don't own one.

As I mentioned previously, I don't think people know how worn their trunnion bearings are, until they are completely trashed. I have had like 5 80's and I work on other people's on occasion, and I have never pulled a knuckle apart that had more than a few thousand miles on it and found perfect trunnion bearings. I have pulled knuckles apart where the races were cracked, and/or the rollers were turning to dust, and there was no indication that there was anything wrong when driving them. @richardlillard1 can probably offer his insight, as he does a lot of axle rebuilds at his shop.

I have seen that some Koyo bearings in various axle rebuild kits have 12 rollers, and some have 13. Notably, I have a bunch of Toyota-boxed Koyos with 13 rollers. I would think that more rollers would equal more capacity, but I've also seen 13-roller bearings show wear with relatively low mileage.

 

[sunrk]

Remember the top kingpin bearings are impossible to get grease to once assembled. The square plug thingy doesn't feed grease to them and is only to top up the grease load inside the swivel hub space on each side. If the swivel hubs are kept very full of grease (remembering they are not a sealed system) some might flow to the top bearings. If during maintenance the top kingpins are taken out it could be possible to inject some grease to feed into the bearings.

It's probable they have lost enough grease that the rollers have worn ever so slightly resulting in 'cogging' as they turn. Replacing the bearings isn't difficult but it's messy and fairly involved.

 

[sunrk]

I see the pattern you mentioned. I'd also think that loose would be felt. Good observation.

I also found Chyna bearings with not only fewer rollers but shorter. Didn't even span the entire race.

Either way I think close attention to shimming is warranted. There's a lot of other people running loaded 80's with large tires out there without short trunnion bearing life. Or is there? I don't own one.

Never ever use anything except genuine Koyo or Timken or SKF for kingpin bearings (or wheel hub bearings). Chyna booster bearings should be used for trailers/caravans only.

Shims under the top kingpins (if needed) set the pre-load and it's important that setting it correct.

 

[NielsC]

I have a fishscale on order, and will check if the rollers slide or roll when setting the preload.
What grease is best for the trunion bearings?
Regular wheel bearing grease, the moly grease, or maybe any other heavy duty bearing grease for heavy equipment?

 

[BILT4ME]

I have a fishscale on order, and will check if the rollers slide or roll when setting the preload.
What grease is best for the trunion bearings?
Regular wheel bearing grease, the moly grease, or maybe any other heavy duty bearing grease for heavy equipment?

The FSM calls out NLGI 2.

I used Lucas Red-N-Tacky 2.
I used Valvoline Palladium with moly in the knuckles/birfs.

Many here have used the moly in both because they will mix.

Both of these lubes are available at most FLAPS.