Should I grease it?

[PitbullMidwest]

I have a John Deere ST46 lawn tractor (mower) and while doing the routine greasing last night I was once again confronted with a question. The mower blade spindles have grease fittings on them but my owners manual clearly states:

"These fittings are for factory use only! Addition of grease may cause the premature failure of the sealed bearings."

I've never greased them before but my inclination is if it has a grease fitting, grease it! So what do you think, grease them or leave them alone?

 

[MJB]

I'd leave them alone. If they went to the trouble of specifically saying that you should not grease them, then there is probably a pretty good reason not to. Just my opinion.

 

[RoyJackson]

Leave them alone!
If you did grease 'em, you invalidate any warranty. And, since they're "sealed", you probably wouldn't get any grease into them anyway.

 

[chrisjbell]

Hmmm. That's really interesting - I have a JD LX277 (think that is the model), and it also has fittings on the spindles. My dealer told me to lube them often - but come to think of it I don't think I've read the actual owner's manual (I bought the big shop manual and use that). I'll have to check, if I can remember....Chris

 

[knucklehead]

Temptation! It's everywhere! You could replace the Zerks with plugs. That might ease the night sweats a bit.

Not helpful, but I couldn't resist. I was tempted.

 

[BigDave]

Telling you not to grease zerks is like someone not to look, people will always try to look, no matter what you told them not to look at.

Anyway, I suspect JD found cheaper/better bearings that were sealed, but didn't go through the expense of changing spindle housing design. If that is the case, replacing the zerks with plastic plugs would have been a good idea. Engineers like to design/improve things, but sometimes they don't always see the big picture.

 

[rancar]

<font color=blue>"...The mower blade spindles have grease fittings on them but my owners manual clearly states:...These fittings are for factory use only! Addition of grease may cause the premature failure of the sealed bearings..."</font color=blue>

This seems to be inconsistent. Why put grease fittings on spindles and then be told not to grease them? I know what moving parts do to friction surfaces that aren't greased. Logically, I can't think this through....how greasing a spindle would cause the premature failure of the sealed bearing. Is this the opposite of if you don't grease it, you will still have failure of the sealed bearing, but it just won't be premature?

If it was me, I would grease it and not worry about it. I have a JD 425 and I grease my spindles liberally as advised by my owner/operator's manual. In my case though I often have to guess how much grease to insert in the fitting as I can't see any joints where the grease emerges as is the case in most other fully packed grease fittings.

Bob

 

[John_Mc]

<font color=blue>Logically, I can't think this through....how greasing a spindle would cause the premature failure of the sealed bearing.</font color=blue>

Not sure how you'd get grease into a true sealed bearing, but if that zerk does feed it into the bearing, I can think of one way it could hurt: In some bearings, too much grease can be as bad as too little. If you fill the cavity completely, the grease you add will most likely be cold. Once you fire up the mower, it heats up. Heat = expansion. Sealed bearing = no where to go. Eventually, you build up enough pressure to blow the seals. Now you're not holding the grease in, and have destroyed your main means of keeping dirt out.

Another problem that can happen: grease expands out of the bearing when hot. After things cool off, the grease contracts. Some is pulled back in to the bearing, pulling along dirt, grit, grass clippings, or whatever happened to stick to it when it was out in the open. Now you've got crud in your bearings which will shorten their life.

Saw both of these things happen on some expensive precision bearings in a couple of wire plants where I used to work.

John Mc

 

[bgott]

You're right. You would be amazed at how little grease is in a sealed bearing. I have screwed up and tore the seals out of a few new ones and there is hardly any grease at all in them.

 

[rancar]

Okay...I can see this. But still, why do they put fittings on the spindles? What's the rationale? For one who doesn't have an operator's manual, this sure is misleading. When one sees a grease fitting, it suggests that it should be greased.