FSM says use wheel bearing grease for trunnion bearings

[Kernal]

Reading the FSM it says to use wheel bearing grease for the trunnion bearings, doesn't mention Moly. But Moly grease is going into the knuckle housing. Over time I would think the two will mix. Any thoughts, just use wheel bearing (Mobil 1 Red synthetic) for the trunnion bearings, just personal preference, no matter either way??

I'll piggy back this question: do new out of the box trunnion bearings need to stay with the race they were boxed with, or no matter??

 

[96r50]

Use moly grease for the trunnions. I don't think the bearings/race will matter as they are unused and have not seated/mated/worn together yet.

 

[Pin_Head]

It is hard to go wrong with the FSM specs, but I doubt that it will matter much. It isn't like the trunion bearings are spinning fast and the little bit of wheel bearing grease on them is a spit in the bucket compared to what is in the knuckle. There is help for OCD.

 

[Kernal]

pin_head, yeah, I got it bad, mostly cause I've never done anything near as complicated as this and as soon as I have it done I leave on a long trip to the north. Don't want to hear any clicks, bangs or grrrrss while in a snowdrift in Virginia. Good news, got my birfs and axles back together, only took an hour of trying first the screwdriver method (no chance), then the hose clamp method which worked after a a few tries and some help from BFH for the short shaft and dropping the long shaft end onto a block of wood.

 

[Tools R Us]

I use moly on them, use whatever makes you happy, but being in the knuckle housing they will have moly in them soon.

 

[Kernal]

Tools R Us: Moly seems to make sense as the trunnions are ??apparently under a lot of stress, but as pin_head says, can't wrong with the FSM specs, assuming it's not a typo.

 

[Cruiserdrew]

Use the Moly grease. If it makes you feel better, use the Amsoil Moly grease which is also spec'ed for wheelbearings.

It's a low speed, heavily loaded bearing, it would make sense that Moly would be specified, unclear why it wasn't, especially given that the birf is right there and packed with moly grease.

I just use the Amsoil moly grease for everthing but the wheelbearings, where I use Mobil1. I also use the Amsoil on the driveshafts and steering linkage.

 

[Chaldaean]

My thinking is:

For a ball that rotates (like the balls in a trunnion bearing) = Non-moly grease

For a ball that slides to provide swivel action (like the balls in a birf) = Moly grease

From recollection of past 'Mud posts concerning moly grease, the solid molybdenum disulfide additive in the grease forms a film on the metal parts that prevents contact of the lubricated parts. If you introduce moly grease to a ball that rotates, the ball will want to slide rather than rotate, which will lead to premature wear.

However, as compared to a wheel bearing, for example, a trunnion bearing doesn't see "that much" rotation, so the choice of moly vs. wheel bearing grease would be less critical.

I think the advice of Mr. T in the FSM is good to heed, though; it's not much additional work.

 

[Kernal]

Thanks all, that step is done. Anyone know if new bearing packs are matched to the races at the factory, or no matter?

 

[-Spike-]

Thanks all, that step is done. Anyone know if new bearing packs are matched to the races at the factory, or no matter?

Probably not, but why chance it?

 

[Kernal]

Yeah, just one more thing to keep track of.

 

[Tools R Us]

My thinking is:

For a ball that rotates (like the balls in a trunnion bearing) = Non-moly grease

Trunnion bearings have rollers, not balls.

For a ball that slides to provide swivel action (like the balls in a birf) = Moly grease

The balls in birfs roll.

From recollection of past 'Mud posts concerning moly grease, the solid molybdenum disulfide additive in the grease forms a film on the metal parts that prevents contact of the lubricated parts.

True of all lubricants.

If you introduce moly grease to a ball that rotates, the ball will want to slide rather than rotate, which will lead to premature wear.

If the lubricant reduced the friction to the point were the roller didn't turn, what would cause the wear? I know of two rigs running moly in the wheel bearings with zero issues. Have cleaned it out of bunches of bearings that showed zero wear issues.

Moly is a great high temp/high pressure/low friction additive that is unnecessary in normal bearings, but it wont hurt them. The main reason that I don't use it where not needed, is it's messy nasty stuff to cleanup.

...I think the advice of Mr. T in the FSM is good to heed, though; it's not much additional work.

Use whatever makes you feel good. But the knuckle is one compartment, there are no seals separating the birf and bearings. The lower bearing lives in a pool of moly, the upper is exposed to moly spray from the spinning birf. So about the fifth time you turn the steering wheel, whatever you put in the bearings is going to be mixed into the birf grease and moly is going to be in the bearings. I prefer to use the same lube in one compartment, rather than having a mix.

 

[Nay]

I always am amused by these threads. On the one hand, we hear about how the 80 can thrive in 3rd world countries on cow s*** grease, and on the other hand we have debates about the properties of synthetic grease as applicable to the parts working within the same cavity.

Perhaps somebody can provide some guidance on how gear oil affects the additive properties of moly grease for the 12-18 months where you know you should rebuild the front end but can't carve out the time to do it.

If you want to care for your trunnion bearings, check your nutz.

 

[Kernal]

The Molys have it, 80:20.

 

[Chaldaean]

Trunnion bearings have rollers, not balls.

You're right. My bad.

The balls in birfs roll.

You're right again. I should have written "don't roll at high speeds" or something.

Rather than rolling vs. sliding, perhaps the choice of moly for birfs is just based more upon performance under high load.

From recollection of past 'Mud posts concerning moly grease, the solid molybdenum disulfide additive in the grease forms a film on the metal parts that prevents contact of the lubricated parts. If you introduce moly grease to a ball that rotates, the ball will want to slide rather than rotate, which will lead to premature wear.

I suppose I'm just parroting what I've read on 'Mud and believe to be true; stuff that seems to make sense. There are just as many posts that say "moly is fine everywhere" as there are that say "moly isn't for...". Some parroted posts, for example: Post 1, Post 2, Post 3, Post 4, Post 5, and Post 6.

Thanks for the corrections, Tools-R-Us (I'm honestly not being sarcastic). I visit 'Mud to [STRIKE]convince myself that vehicle mods are necessary and I that I can spend more money on stuff because I have access to the knowledge to carry out the work myself[/STRIKE], read different perspectives, to generally learn about my rig, become familiar with vehicle systems and read funny stuff.