Spindle Bearing Lifespan?

I just purchased a new Gravely ZT HD 44 mower. The dealer told me the mower deck spindle bearings are sealed and cannot be greased.

My previous mower had zerk fittings for greasing the bearings, so I'm a little concerned about this. I will only be using this mower on my 1/2-acre yard, so it will have an easy life with no commercial applications.

Are permanently-sealed bearings really permanent, or will I have bearing replacement issues in a few years?

(When I was a teenager, my dad purchased an Ariens Fairway Four riding mower. It resembled a Snapper mower and had a 4 hp Briggs and Stratton engine. We used that little mower for at least ten years. Tough little machine!)

The maintenance free spindles usually last about 2-3 years in commercial use. It has been reported that the bearings are replaceable but I have no experience with them.

Richard-TX said:

The maintenance free spindles usually last about 2-3 years in commercial use. It has been reported that the bearings are replaceable but I have no experience with them.

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I am sure( I think) that Bearings Inc has the replacement. But then there is the labor - $60 to $120 per hour.
IMO, zerks are better, but they must be used, of course....Particularly after a deck wash down.
And the rubber boots to protect the bearing is important, no "sealed" bearing is sealed 100%.

Greasing ball bearings is tricky business. Too much grease is as bad as too little.

For those that don't get alot of exposure to the inside of spindles I will tell you that most of the newer ones I see are sealed bearings even if it has a zerk fitting on it, Trouble is for those that actually use a grease gun they over do it, if the spindle does not have a pop off relief then what happens is they blow the bearing seals right out of the bearing due to over pressureization, at that point the bearing is basically dead as everything in the world can get into it, The one or 2 commercial brands that tried actual greased bearings found they had more problems and complaints with them , By using sealed bearing with a pressure relief on the spindle everybody is happy, for those that don't grease they still get "normal" wear on thiers and the guy with a compulsive grease gun addiction he can pump grease in them all he wants and thinks he is doing good. The only good that any grease does on these is make it a little easier to get things apart should they need to be repaired.

Double sealed ball bearings are not meant to be greased....ever. The problem is that the grease pack is not supposed to be no greater than about 30% by volume, less if the bearing is operating near it's maximum rated RPM, slightly more if low speed. Since this is a mower spindle, the operating RPMs fall into a medium speed so a 30% pack is called for.

By virtue that there is no way to determine what the bearing grease pack is, it will get over greased. Overgreasing causes the bearing to overheat which results in all manner of bad things occurring. The reason for the overheating is that the balls have to plow through the grease instead of rolling in the race.

A one side sealed bearing would be a reasonable choice for a mower spindle but the necessary relief port is required but that also leads to problems in keeping the upper bearing lubricated properly. Grease will run down to the lowest point over time.

For those contemplating replacing the bearings in a spindle, there is more to it than just replacing bearings. The necessary axial free play/preload can be a challenge to set correctly and it does change from bearing manufacturer to manufacturer. Without several hundred dollars of precision measuring tools, the best advice I can give is to use the same manufacturer of bearing that the spindle was originally equipped with. At least there is a reasonable chance that the axial freeplay/preload will be set correctly. Using a different makers bearings will be very risky at best.

Richard - Who makes and repairs High Speed Spindles

One of the most common cause of bearing failures ------- Hitting objects with the blades. After hitting things and ever so slightly bending the jackshaft, it will cause it to ruin the bearings as well as the rest of the spindle assembly. Solution ----- DO NOT HIT OBJECTS WITH YOUR BLADES.

Sounds simple, I know sometimes you don't see stuff int he grass but you should make an attempt when you do see stuff, or walk the yard and make sure there is nothing. We have sold Gravelys for 10 years and has been the least replaced spindle out of any of them. The spindles will last if you do not abuse them.

What I have found regarding bearing and striking stationary objects isn't so much bending of the shaft, but actual damage to the bearing. In extreme cases brinelling is very obvious as in the picture below. In less severe cases a magnifying glass may be required.

Brinelling is a fairly common type of damage. I have pulled brand new bearings out of the box to find them brinelled due to rough handling by UPS or improper packaging.

I see a fair amount of bearings in a year. My bearing bill last year alone totaled over $2500.00 There were no special bearings in that. Most were common 6200 series ball bearings. I would say that about 10% of the bearings I replace failed due to brinelling. The #1 cause that I see for premature bearing failure in mowing equipment is corrosion due to the ingress of water.

I have a 1982 Whel Horse C175--Original (greasable bearings)
I have worked on MANY lawnmowers and will give my personal opinion.
Quality machines of yesterday, had greasable bearings with the right engineering in mind.
W H Gravely and others had bearings that were sealed on ONE SIDE. Bearings were installed with Seal up on the top bearing and installed DOWN on the lower bearing. The seal --on bottom-- was installed (backwards) to allow escape of grease below the deck. Had the lower bearing been installed to prevent grease escape, over greasing would blow either the top or bottom seal. If the seals are not installed in this fashon there should be a way for the grease to escape:thumbsup: I have seen some machines that had an open bearing on the bottom with a rubber washer, or felt, with a thin metal plate covering them.
My old WH and Gravely evidently have this seal configuration because grease escapes below the deck, not on top that would contaminate belt:thumbdown:
Some machines that I worked on Years Ago were designed this way but I have not seen this in modern machines.
I think it would be wise to use a hand grease gun with only Two or Three pumps unless you are sure of grease escape.
To not discredit some of you that have "permanently sealed" ????? they are cheaper to manufacture and most people would never grease them anyway
I am a retired Tool&Die Maker and I would much rather have greasable spindles:thumbsup:

Since you are a tool and die sort of fellow, I think you will appreciate the following.

The later 40" and 50" Gravely mower decks used no-contact, labyrinth seals with tapered roller bearing in their spindles. This eliminated all of the issues regarding seals and greasing.

Excess grease contaminating the belt is not an issue as the pulleys sling any grease away from the belt.

The only problem with the labyrinth seal is that most shade tree mechanics has never seen or even heard of it let alone know what it is and how it works.