How Much Grease in Steering Knuckle (1 Viewer)

[94 Newbie]

Pardon my ignorance, but ...

Why is Moly grease so important for the knuckles as opposed to disc brake wheel bearing grease, which is what both my knuckles are now filled with as of last night.

I always find the info I need after the fact ! :whoops:


At any rate, I have owned several older ( 70's ) Dodge Ram Chargers w/ full time 4 wheel drive, and the practice for grease gun lubrication of the wheel bearings , which were tapered roller Timkens, was w/ disc brake grease.

I figured it must be good stuff to hold up to those temps & conditions - what am I missing ?

Thanks !

Britt

P.S. This time, the search found some cool info !

 

[scottm]

Moly is very slippery against moly, and it attaches itself to metal. This is great for heavy friction between sliding metal parts, like gears and bushings. Roller bearings eliminate heavy sliding loads by putting rollers between the metal parts. This results in much less surface taking a much higher load, but it's rolling. Grease cushions the contact surfaces, fills in small voids, and dissapates heat. If the rollers slide, the sliding surfaces are very heavily loaded and wear quickly, wearing through their hardened outer surface, and creating flat spots that continue to slide.

Moly is bad for roller bearings for two reasons: moly is too slick, and moly builds up on metal surfaces. Imperfections and debris can cause the rollers to stall and slide without enough friction, and friction isn't that significant in roller bearings. Moly builds up unevenly, in patches, so the rollers can get uneven and slide. Tight tolerances in roller bearings can get even tighter under load and heat, and moly buildup on the surfaces can further tighten things, to overload and overheat bearings.

So, sliding surfaces are great with moly, rolling surfaces, not so great. CV/Birf joints have balls, but they're sliding surfaces. HTH.

 

[tarbe]

Good explanation Scott.

This is why I use moly grease in my slip yokes.

 

[Cruiserdrew]

Moly is very slippery against moly, and it attaches itself to metal. This is great for heavy friction between sliding metal parts, like gears and bushings. Roller bearings eliminate heavy sliding loads by putting rollers between the metal parts. This results in much less surface taking a much higher load, but it's rolling. Grease cushions the contact surfaces, fills in small voids, and dissapates heat. If the rollers slide, the sliding surfaces are very heavily loaded and wear quickly, wearing through their hardened outer surface, and creating flat spots that continue to slide.

Moly is bad for roller bearings for two reasons: moly is too slick, and moly builds up on metal surfaces. Imperfections and debris can cause the rollers to stall and slide without enough friction, and friction isn't that significant in roller bearings. Moly builds up unevenly, in patches, so the rollers can get uneven and slide. Tight tolerances in roller bearings can get even tighter under load and heat, and moly buildup on the surfaces can further tighten things, to overload and overheat bearings.

So, sliding surfaces are great with moly, rolling surfaces, not so great. CV/Birf joints have balls, but they're sliding surfaces. HTH.

That is the conventional wisdom but why does the valvoline, and Amsoil Moly grease say that's it's good for wheel bearings? I've used it previously in a front repack with no issues at all. Ford even specs moly grease for thier front wheel bearings. I suspect there is more too it, and it may have to do with the form or concentration of moly that is used.

 

[96bruzer]

Just wanted to share the dark green gear oil coming out of my diff.

After reading all this now I think I understand what happened to my front diff.

I filled my knuckles through the square hole all the way till the grease oozed out while my grease gun was in there, drained and refilled my diffs and now checked my front diff because I was hearing a whinning noise and viola dark green diff oil coming out.

Now I think I will try to flush with cheap 80/90W a couple of times and re check.

Any other suggestions?

By the way, I also have a new thread asking about (nobody has replied yet, still waiting) this till I saw this one, thanks!

https://forum.ih8mud.com/80-series-tech/473541-front-diff-noise-contamination.html

 

[fuzzywuzzy]

I've read through this thread and this: Front Axle Rebuild - For FAQ thread and this video from Jonsey's regarding the axle rebuild and I still have a question. I'm seeing most people in this discussion are recommending that you should fill the birf itself full before putting the axle in place and in the video Jonesy's put's a 4 oz tube of moly lube in the birf before adding the axle. No issues there.

Jonesy's puts two additional 4 oz tubes in the knuckle after reassembling the axle out to the rotors. Now here is where my question comes in... each of those tubes is about $4-5 so I'll be $30 in for the full axle. I can get a single 14oz tube of the Valvoline with moly for about $5, much greater value. So Jonesy's put's 8 oz in, if I chose to use the Valvoline should I just shoot for 8oz? I only ask because he had everything closed up before adding the grease so there's no way to tell how much of the knuckle's volume was filled. I'm guessing that the grease doesn't ooze out if I keep the knuckle open when adding the grease to the 2/3-3/4 volume?!

Can anyone shed some light on this?

 

[Shoredreamer]

I've read through this thread and this: Front Axle Rebuild - For FAQ thread and this video from Jonsey's regarding the axle rebuild and I still have a question. I'm seeing most people in this discussion are recommending that you should fill the birf itself full before putting the axle in place and in the video Jonesy's put's a 4 oz tube of moly lube in the birf before adding the axle. No issues there.

Jonesy's puts two additional 4 oz tubes in the knuckle after reassembling the axle out to the rotors. Now here is where my question comes in... each of those tubes is about $4-5 so I'll be $30 in for the full axle. I can get a single 14oz tube of the Valvoline with moly for about $5, much greater value. So Jonesy's put's 8 oz in, if I chose to use the Valvoline should I just shoot for 8oz? I only ask because he had everything closed up before adding the grease so there's no way to tell how much of the knuckle's volume was filled. I'm guessing that the grease doesn't ooze out if I keep the knuckle open when adding the grease to the 2/3-3/4 volume?!

Can anyone shed some light on this?

That's a great video, but one problem IMO is he way underfills the knuckles with grease. 12 oz. per side is nothing. Plus when you fill thru the fill plug on the outside of the knuckle, that grease mainly runs down onto the outer birf. You want grease on all surfaces. - Inside the inner knuckle, on the exterior of the inner knuckle (smooth visible part connected to the axle body), inside the outer knuckle, inside the birf, outside the birf and inside the spindle. I followed this video and used the CV joint grease he used and had rust show up at the top trunion bearing area. The grease never made it up there. I did another rebuild last week with 5 14oz. tubes of Valvoline Palladium (2.5 tubes for each knuckle). Packed it with grease as I put everything together. Much better.

 

[Hornd]

I do the zip tie test thru square fill hole on top of knuckle body(2/3-3/4) then pump till my arm hurts (I know, I know) with Grease Gun Loaded with Valvoline Palladium. It's a 10 min and $10 Job.

*Chk the bottom 2 bolts that are pointing to the ground to ensure tightness (turn clockwise). These are the Trunion Bolts.
**Also ensure the 2 bolts holding on Caliper are tight.



***The bottom two items will keep you from making a post telling everyone to do the same.

 

[DirtScaresMe]

Hop under your wagon and have a look , If you are not sure what you are looking at I suggest you get an en expert to rebuild your front end while you watch and learn.

Over 10 years old, but I really have to disagree. If you research the tools, technique, and parts this is a job anyone of moderate skill can do. Even low skilled, like me.

 

[midfat]

I just pull the ABS sensor to physically LOOK inside the birf. A 1" hole beats a 3/8" hole almost every time.

 

[DirtScaresMe]

I just pull the ABS sensor to physically LOOK inside the birf. A 1" hole beats a 3/8" hole almost every time.

So many jokes, so many jokes.

 

[fuzzywuzzy]

So what I'm reading from @Shoredreamer is that I need to have the knuckle open when adding the grease then complete the installation of spindle et al. The feedback from everyone has been very appreciated!

 

[DirtScaresMe]

So what I'm reading from @Shoredreamer is that I need to have the knuckle open when adding the grease then complete the installation of spindle et al. The feedback from everyone has been very appreciated!

Are you talking routine maintenance? Opening the entire knuckle up to add grease every few thousand miles seems a bit extreme.

 

[fuzzywuzzy]

Not routine. Just bought it and it needs it.

 

[DirtScaresMe]

Ah, yeah. That's what my driver's side looked like last fall. I limped through the winter, my driveway stinking like gear oil. It's a really cool job provided you have the tools/time/prep. I'm sickly looking forward to doing the other side this summer.

 

[fuzzywuzzy]

I'm geeked out looking forward to it. I've collected the extra tools I needed, got the kit from Spectre, and gotten the chemicals I'll need (need to get some more grease now and a grease gun). All that's left is finding time.

 

[DirtScaresMe]

I'm geeked out looking forward to it. I've collected the extra tools I needed, got the kit from Spectre, and gotten the chemicals I'll need (need to get some more grease now and a grease gun). All that's left is finding time.

Four items I didn't see referenced that really helped me:

• brass hammer
• 1.5" ID pvc pipe, about 4' long
• several (~6" thick) cardboard
• bunch of newspaper / packing paper.

The pipe is to separate the birfield from the inner axle. The cardboard and packing paper is to make sure the axle doesn't javelin itself into the ground and get marred. The brass hammer is for you to give to someone else to smack the axle as you press the clip together with screwdrivers, sitting indian style, with the axle over your shoulder.

That whole affair was easily the most time consuming. Once you've gotten the technique down (I didn't have a pipe and tried the ziptie/hose clamp trick to no avail), it's cake.

 

[Shoredreamer]

So what I'm reading from @Shoredreamer is that I need to have the knuckle open when adding the grease then complete the installation of spindle et al. The feedback from everyone has been very appreciated!

Yes when you're doing a rebuild it's easiest to apply the grease in the knuckle as you rebuild. But for routine maintenance, yeah just use the fill hole on top. Have fun with your rebuild.

 

[greentruck]

Not routine. Just bought it and it needs it.

You can add grease if it needs it now, but you're not ready to do the axle service. Just need to remove the plug, then pump it in. As someone noted earlier, the tip of most grease guns fits the opening.

If you clean up the outside of the birf where it's thickly caked on and overflowing, that will give you an idea of how quickly it's leaking. It may turn out the thing was never cleaned up and the leakage isn't as bad as it looks.

 

[fuzzywuzzy]

@greentruck - I've already bought everything and if it's leaking at all I should get it fixed, besides. I'd rather repair the issue than just adding diff oil and grease to the knuckle.

@DirtScaresMe - the guys who's going to be my second set of hands has the pipe and I was going to do the paper trick and a 2x4 for extra safety for the floor and axle. I don't have a brass hammer (I've got ball peen, framing, rubber mallet) but got hose clamps, hoping I can make it work for now.