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Thread: Wheel bearing life extended by periodically repacking?

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    Walmart greeter Mikes Z car's Avatar
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    Default Wheel bearing life extended by periodically repacking?

    Since the front wheel bearings are easier to repack with grease they tend to be greased much more frequently than rear wheel bearings, right? Do front wheel bearings tend to last a lot longer because of this indicating there might be wisdom in periodically re-greasing rear wheel bearings assuming there is a procedure for this? I have heard of a pin injector like used for putting air in basketballs that can be used for wheel bearings, don't know if that might work with an early Z.
    Last edited by Mikes Z car; 07-07-2014 at 05:29 PM.

    70 240Z HLS30-00907, 1/70, wiper motor 97 Accord, Dave's harness mods, turn signal relay mod, quartz movement in clock, map light fixed, connectors cleaned/greased, 60A alt w/ NOS voltage regulator, weatherstrip replaced, defroster grid replaced, undergoing rust prevention. Previous owner of 71 240Z, 8/71, HLS30-41545, last seen in Sacramento painted blue (originally orange) has anyone seen it?

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    Nova Scotia,Canada,Earth Blue's Avatar
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    It's difficult to get at the rears to re-pack.

    Bicycles have passages in the hubs for forcing in new grease that pushes out the old.

    I bet this could be done with the rear hubs but the volume of grease in the central cavity is very large. This would have to be filled first in order to use the bike hub method.
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    Walmart greeter Mikes Z car's Avatar
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    Is there room to put a zerk fitting in the hub or would it bump into something else? I am not sure from what you said if it would be a good idea to even try it.

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    The front bearings are tapered roller bearings, the rears are ball bearings. May not matter.

    Seems like the automakers would have installed a Zerk fitting if it needed it. I don't think that re-packing the front bearings is even a maintenance item either. I remember re-packing the front bearings on my 78 B210 a few times but in retrospect I don't think it was necessary.
    1976 280Z, with some minor modifications

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    Rust Free'ish zKars's Avatar
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    Here is a pretty good description of how and why wheel bearings fail and the contributing factors.

    toyotaoffroad.com/Articles/Projects/Bearing_Failure/Bearing_Failure.htm

    There are several points that are relavent to our discussion. Breakdown due to age and heat, contamination, and too much grease are listed issues.

    It would be nice to be able to re-grease the rears occasionally and that would no doubt extend their life, but the design and labor required makes it unlikely that anyone would actually take the time to do it.

    Note that the advice in the above link refers to front type conical bearings with a separate race and bearing, not sealed rear ball bearings when they talk about periodic maintenance.

    Edit: the 71 FSM lubrication Chart has a "change wheel bearing grease" every 30,000 mi..." I'm pretty sure they just mean front... Still, a very short interval. And "Change", not, Clean, Check adjust or supply.
    Last edited by zKars; 07-08-2014 at 08:54 AM.
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    Jim
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    I looked for maintenance information on the wheel bearings but couldn't find it. But now I see that it's also in the Owner's Manual. Since becoming an FSM advocate I almost never look in there anymore. Thanks for the tip.

    By 1976, maybe earlier, they were down to 25,000 mile intervals. As your link points out though, one cause of failure is contamination during repacking. It's a dilemma. Probably worthwhile to get one of those grease packing device to reduce handling if you're going to do it.
    1976 280Z, with some minor modifications

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    Crumudgeon
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    The rear wheel bearings on the S30 last a couple hundred thousand miles with normal road use. How many more miles do you guys want?

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    Walmart greeter Mikes Z car's Avatar
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    I like to shoot for forever when doing maintenance realizing there might be some unobtanium in that idea. The Toyota Tercel that is my DD went 179,000 on the rear bearings before they needed replacing. I actually had two of those cars back in the old days and the other one went to a similar mileage before the rear bearings started getting noisy.

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    The rear wheel bearings on my 1970 had 150,000 miles on them when I pulled them off during the resto. They were working perfectly but I was replacing everything wearable.
    As I remember, the inside bearing behind the seal was open and was packed with some pretty hard grease, the outer bearing was sealed on both sides.
    Both or I should say all four bearings where replaced with sealed bearings.
    Anyone else find the same thing?
    Chris

    Quote Originally Posted by John Coffey View Post
    The rear wheel bearings on the S30 last a couple hundred thousand miles with normal road use. How many more miles do you guys want?
    1970 240Z HLS30 01955 March/70

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    Walmart greeter Mikes Z car's Avatar
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    Thanks zKars for the link to bearing failures and to everyone for the great information.

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    Rust Free'ish zKars's Avatar
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    Quote Originally Posted by grannyknot View Post
    The rear wheel bearings on my 1970 had 150,000 miles on them when I pulled them off during the resto. They were working perfectly but I was replacing everything wearable.
    As I remember, the inside bearing behind the seal was open and was packed with some pretty hard grease, the outer bearing was sealed on both sides.
    Both or I should say all four bearings where replaced with sealed bearings.
    Anyone else find the same thing?
    Chris
    Granny, you bring up a couple of interesting areas for a further discussion!

    In the article I found, he mentioned a few words about how wheel bearing grease works. It has two parts, a carrier, the heavy thick stuff, and the actual oil that is extracted from the thick stuff that fills and lubricates the bearings.The balancing act is having enough volume of "grease" (both parts) to keep the lube action going for it lifetime. Eventually the grease breaks down and goes hard and waxy. I've seen in lots of old bearings. Hopefully this happens at the end of the service life (150000-200000 miles)

    All the stock bearings I've seen only have one integral seal on the outside of the inner bearing, all of the other three bearing faces are open to the housing guts. This implies you need grease everywhere in the housing to keep these supplied. I'm a bit worried about grease life with having bearings that are sealed on all four sides that have a much reduced volume to use. It also makes me think someone before you replaced those bearings.

    This all assumes that the total grease in the bearings and in the axle housing warms up and thins out enough so that there isa net flow of grease throughout the space over time. Otherwise what is the point of having (some) grease in the axle cavity front or rear if only the grease in the bearings themselves is doing anything? It hard to find information on "axle grease flow dynamics"....
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    Crumudgeon
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    Adding a zirc fitting or penetrating any of the seals to add or change the grease will just create an avenue for contamination. And a sealed bearing is not a panacea, look at Porsche's problems with the intermediate shaft bearing on the M60 Boxster and Carrera engines as a perfect example.

    And regarding grease "flow" into the rear hub bearings... I've opened up a few dozen rear hubs and have yet to see evidence of grease flowing into the bearings from a packed housing. I may not be smart enough to see if that occurs but most of the grease packed in the housing has solidified and only "flows" when I scrape it out with a putty knife.

    I know packing the housing is a step in the FSM but its not something I do when I rebuilt them. I just use a grease (Wurth SIG3000) that didn't exist back in the 1970s and is orders of magnitude better then what's spec'd by Nissan.
    Last edited by John Coffey; 07-09-2014 at 08:53 AM.

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    Rust Free'ish zKars's Avatar
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    John, wise and experienced thoughts indeed. No surprise that we are overthinking this. Buy the best grease you can find, pack your bearings properly, throw some in the housing if you feel like it, and forget it about for 10 years.

    Yet I can almost guarantee you that at least three of "us" will now go and mock up an experiment with a rear axle housing and freshly packed bearings, where a propane torch and an electric motor are involved. They will measure 3D grease displacement at varying temperatures and centrifigal force values, and will plot the results in an excel spreadsheet. Only they will find that no matter what they do, the grease just stays in the bearings.... like its designed to do....
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    73 240Z HLS30 149331
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    This is work related and a bit off topic, but I still think its worth mentioning.

    We had Electomotors with grease nipples to gease the bearings in our water treatment plant. The technicians greased them in there rounds with 3 grams of grease as per manufacurers instructions. These motors where installed in 1998 and were all replaced by 2002 mostly due to bearing failure.

    I had them replaced with motors that had sealed bearings filled with Hi-temp grease. Nearly all (14 of the 15) are still in use today, but some are starting to develope signs of bearing wear that shows up in the vibration analysis we do every six months. These motors run all day every day for Purified water, WFI, and Cooling / heating medium systems.

    My conclusion; A sealed bearing lasts longer because it does not get contaminated by dirty grease or when someone pumps in to much grease and pops the dust seals allowing dirt and other contaminates in.
    Common causes for bearing failure is contamination or undersized / underrated where the pressures in the bearing increases above the design limit and causes it to overheat at which point the grease fails to lubricate and it fails.

    I think lubricating them could reduce there life span more than increase it. Like John said in his post, most rear wheel bearings last the life of the car or at least 100,000miles without relubricating.

    Chas
    Last edited by EuroDat; 07-09-2014 at 12:33 PM.
    Chas
    5/77 280Z HLS30 403100 with some modifications
    Original colour: 305 Light Blue. The PO changed it to Red

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    I've thought about what the grease does at high temps and spinning as well, and I've come to the same conclusion as John Coffey. I don't think it goes far and it certainly doesn't liquefy. When I took my old rear wheel bearings out, it was clear that the grease never left the immediate areas of the bearings. There wasn't a lot in there and it was all located by the bearings. I had to use mechanical means to remove it.

    When I put my bearings back together, I packed the entire recess completely full on the first one. Took about half a tub of grease. a strikingly large amount.

    After I got done with the assy, I tested the turning torque required to spin the hub, and it was too much. I didn't measure it, but clearly way more force than it should take to spin. Like the grease was trying to get out of the way of the balls, but just had no place to go.

    When I did the second hub, I packed the balls with grease and a little extra and put the thing together. Felt just like I would have expected it to.

    So based on those results, and because of where I found grease on the original bearings when I did the disassembly, I took the first side apart, scooped out most of the grease and put it back together again. Feels perfect and matched the other side.

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    Administrator bpilati's Avatar
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    Why bother greasing the rear bearings when they last so long? Unless it's a daily driver they'll last over 40 years like mine.
    Bryan Pilati
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