greasable u-joints vs. non greasable


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Old 08-05-2012, 04:13 PM   #1
TheGreenMachine
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Default greasable u-joints vs. non greasable

me and a buddie were having a conversation about u-joints today..ive been needing some new ones for my xj and settled on the moog greasable ones, he was telling me though that you want the non greasable ones because they are stronger..his argument was that they are solid and not hollow in the middle like the greasable ones are..not sure what to get now, ive always heard that your u-joints should be your weakest point because they are inexpensive..any ideas? running a 3 inch suspension lift if it matters any


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Old 08-05-2012, 04:28 PM   #2
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anyone can go on and on abou the strength of any u joint, but nomatter if its a 10 or 60 dollar joint, the only thing keeping it operational is the grease. I perfer the greasable only cause i feel like if the grease gets out of it i can re grease before having to replace. plus you can get a nice quality grease compared to a poor quality one that many good u joints come with. i think it mostly comes down just to personal opinions
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Old 08-08-2012, 01:42 AM   #3
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Theoretically, the non-greasable Cardan joints are incrementally stronger, due to the lack of the drilled port for the zerk on the middle of the cross (the trunnions are usually still hollow.)

However, if you maintain them properly, the greaseable ones will last a good deal longer, since you'll be able to flush contaminants out of them when you grease them (every 3, 6, or 12 months - depending on usage patterns, operating environment, &c. The harder you use them, they more you should grease them.) You won't be able to flush the non-greasable units, which allows any accumulated contaminants to work on the bearing rollers and accelerate wear (and decrease longevity.)

If you want a stronger joint, you're going to have to find an exotic part to get it - or have a part custom-made (4140, 4340, 8620 cross & caps, Oilite bushings, heat-treatment and cryo-treatment of steel parts, ...)
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Old 08-08-2012, 08:56 AM   #4
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Quote:
Originally Posted by 5-90
Theoretically, the non-greasable Cardan joints are incrementally stronger, due to the lack of the drilled port for the zerk on the middle of the cross (the trunnions are usually still hollow.)

However, if you maintain them properly, the greaseable ones will last a good deal longer, since you'll be able to flush contaminants out of them when you grease them (every 3, 6, or 12 months - depending on usage patterns, operating environment, &c. The harder you use them, they more you should grease them.) You won't be able to flush the non-greasable units, which allows any accumulated contaminants to work on the bearing rollers and accelerate wear (and decrease longevity.)

If you want a stronger joint, you're going to have to find an exotic part to get it - or have a part custom-made (4140, 4340, 8620 cross & caps, Oilite bushings, heat-treatment and cryo-treatment of steel parts, ...)
Thanks for all the info! Im leaning more and more into the moog greasable ones
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Old 08-08-2012, 01:38 PM   #5
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not even a question, geasable is the way to go, the body may have grease hole but that is not where they break, and most all u-joints have at least a grease "resivoir" if you will, a hole in the trunion as mentioned previously.
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Old 08-08-2012, 09:58 PM   #6
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Some where there has to be data on greasable u-joints vs. non greasable and their strength. I am sure that the non greasable are stronger but the question is, "how much stronger" than the greasable. If that data could be found it would solve this question once and for all. I am sure that the manufactures have data on their particular u-joints.
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Old 08-08-2012, 10:57 PM   #7
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I read on Jeep forum a long while back about this. The discussions went back and forth. Of course I can't find the thread now but the final result was non-greaseable (sealed) was stronger UP TO 20% stronger than greaseable.. The question is 20% of what force/torque?

I see more U-joint straps broken than U-joints failing unless they are old or never serviced.

It kind of depends on what type of usage you're going to get out of them. If you're doing mud, greasable all the way. If you never plan on never touching mud and just doing rocks, you could go with sealed. On my shafts and axle joints, everything now is greasable because we are predominantly mud here and I got tired of changing axle joints every other trail ride.

I personally like the Spicers. They are very strong and very affordable.
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Old 08-11-2012, 08:13 PM   #8
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^ I agree with Lyon! I feel even if your not in mud or sandy environments all the time you should put in greasable joints regardless. One like others said they will last a lot longer when properly maintained and eventhough it can be a pain in the a$$ to get under and grease all the time it worth it in the long run. It like a piece of mind knowing that everything is greased. Also if your breaking the straps that hold them into place they make those little u-bolt upgrades for them as well. But i carry a couple extra u-joints in my jeep at all times just in case though so im not to worried.
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Old 08-12-2012, 05:57 AM   #9
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If the strength of the joint is a concern you can buy high strength u-joints. The difference is instead of a hole in the middle of the joint for the zerk there is a small hole in one of the end caps that you grease with a needle tip on your grease gun. The channels that carry the grease internally are smaller in diameter and the lack of a hole in the cross section for the zerk greatly increase the joints strength yet still allow lubrication for service or after water entry.
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Old 08-15-2012, 11:35 AM   #10
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This was actually argued a long time ago on Pirate (they were comparing for a 60 but it's the same concepts).

http://www.pirate4x4.com/forum/showt...oint%29---just

as mentioned earlier, all off the shelf ones have the grease paths through the middle, the only difference is if the zerk fitting is drilled or not. GED make a great post in there explaining the driving force on the fitting and how you can actually bypass most of that wakness.

Quote:
Another comment regarding those of you who want to run the greaseables. I am in agreement with the comments about the crossed drilled portion not being a big issue for overall strength. The area of concern is the hole between the trunnions for the zerk. What you will find is that the hole is much stronger in compression than expansion and this is in fact relevant. You can orient your joints so that the hole is on the compression side when driving force is applied. ( this of course will not be of benefit while backing up!) Take a close look at the joint and visualize that the inner axle provides the driving force thru the joint and to the outer axle. You will orient the zerk hole so it is in the compression side between the yoke ears. This is an old racing trick to get maximum possible strength. I work in a driveshaft shop and have seen many examples of u-joint failures that are directly thru the zerk hole. This will apply for driveshaft joints as well. It will position your zerks 90 degrees apart on the driveshaft so greasing will generally require you to rotate your shaft to get the grease gun on but it may be worthwhile for those that are experiencing failures.
As well, the SPL series joints are stronger for a couple reasons, one indicated above regarding contact area of the rollers but also because the body of the joint is cold forged which increases strength of the material.
Pretty much that means put the zerk fitting towards the driving side (towards the transfer case in the drive shafts and towards the pumpkin in the axles) and that will be putting the zerk fittings on the compression side, which they're the strongest in. While this won't guarantee that they won't break, it will take a bit more force for them to actually start cracking at the zerk fitting.


As to the question, I always run greasable. I like being able to service everything in my Jeep, but this has a lot to do with personal preference.


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