How often should the front center-ball be serviced on rigs with unlocking hubs that don't see mud or river crossings?
My front DS only spins when I hit the trails.
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Questions for Shawn at Tom Woods
- Thread starter AndyG
- Start date
How often should the front center-ball be serviced on rigs with unlocking hubs that don't see mud or river crossings?
My front DS only spins when I hit the trails.
@AndyG has my vote for the replacement Jerry. Change your avatar, man!
OP
OP
Hey man, it’s 2024! You never know
Oh boy.
Maybe I need to rethink being on here so much.
This is gonna hurt.
This is one of those things where eventually I'll make a video breaking down the differences between the different types of joints. I have some joints that I've done a cross-section cut away on to show the inner details of the joints. The plan is to measure out and compare all the dimensions and do some harness testing to different points on the joint. It's important to note that most of the joint failures we see are wear related, not physical breakage due to too much torque. That being said, I do believe the non-greaseable joints are stronger, the question is: how much stronger?. This seems to be a closely guarded secret from the joint manufacturers. I've tried multiple times to get some clear data from both Spicer and Neapco. The only thing either of them has been able to provide was some charts that show how much stronger theirs is compared to the "Leading competitor". It seems quite paradoxical though because Neapco must be Spicer's leading competitor and vice versa, yet they both claim to be multiple times stronger than their leading competitor. Also, Spicer only shows "fatigue cycles to failure" but they don't explain what that means. Neapco shows fatigue cycles to failure but they also have a graph with "Ulitmate strength" in Newton-metres. The problem is, they don't have numerical values on this chart, so we are left guessing how many newton-meters a joint can handle before breaking. It is my believe that they are vague about this for a reason. I suspect that the actual data would not be as impressive as they want you to believe.
Much less often. But I still think once a year or so is a good idea. Simply because there's no harm in doing it more than necessary and it gets hot under your Jeep, the grease will break down, melt, and vacate the centering ball over time, even if the shaft is not spinning.
OP
OP
Have you ever seen the Weird Al celebrity interviews?
They are hysterical
He takes real interviews and makes up his own questions.
OP
I can shed some light on this based on my experience in that world (design engineering in the automotive and power sports industries.) Marketing folks like comparisons, but lawyers don’t. So, they compromise. The vagueness (not naming the competitors and not giving test specifics) satisfies the lawyers, and the marketing folks don’t really care because they don’t understand the tests and assume the general public wouldn’t either. They’ll not release that information because the lawyers want the vagueness to keep from getting sued. The truth in advertising rules only require you to have test data to back up your claims, but that data doesn’t have to be made public, and keeping it private makes it difficult for a competitor to prove you wrong. They’d have to sue, but since they are not specifically named as the competitor, and there are no details regarding the tests or the results, that (suing) doesn’t make sense to them. It’s like trying to nail Jell-O to the wall.
Here’s how I would have tested these if I was the design engineer. For the fatigue cycles to failure I’d run the u-joints in a very stout pair of yolks on a dynamometer at a constant load (torque) and fixed deflection angle and count the revolutions until the joint fails. As the joint makes a revolution, the loads on it change direction as it accelerates and decelerates, so each revolution is a load cycle. There are a lot of details that need to be worked out, and that’s part of the beauty of the vagueness the lawyers like. How do you replicate something that can’t be replicated?
As for the ultimate strength testing, I’d put the joint in another very stout pair of yolks, and then I’d run it in a torque testing machine (Instron makes them), where it would be twisted to failure, while recording torque and angular deflection. By looking at the torque/deflection curve, you can see the point of failure clearly and determine the torque at that point, which is the ultimate strength.
I am not Shawn but I have a week or two of building driveshafts under my belt so here is my $.02
1. What is the biggest mistake owners make installing drive shafts?
Using improper or poor hardware. You need to make sure the strap, bolts and associated hardware are of good quality and working order. Commonly Ujoint straps are reused when ideally they no longer are properly retaining the joint cap and allow it to spin. Also making sure the fasteners are the correct length especially on double cardan shafts.
Also making sure to lubricate greaseable parts after installation. A lot of times folks do not make sure that things a properly lubricated prior to install so make sure to properly lubricate after.
2. What is the most common mistake installing u joints?
Being too rough and not maintaining cleanliness. I see a lot of yokes damaged by overzealous hammer use or the use of a ball joint press. Also not making sure to prevent contamination of the bearing and seal.
Lubrication. Not making sure greaseable parts are greased or adding excessive grease to non greaseable things like Spicer Life ujoints.
3. How often do shafts need serviced?
Shawn is absolutely correct on it depends on what parts are used and the conditions they are used in. General rule I recommend is regular greaseable ujoints under normal driving should be greased at 3500 miles or so. Hard off-road use or playing in the wet you grease after each run. And remember that you really cannot overgrease a ujoint. You need to make sure that clean grease is coming out all four caps to ensure that contaminates and the old grease has purged.
4. What kind of grease is best?
Spicer recommends Chevron Ultra Duty EP2 (or their fancy Calcium thickened synthetic) which is a good high temp red lithium grease. Ideally any quality high temp bearing grease used often will net good results. One thing to avoid is any grease with Moly in it as it has a tendency to keep the needles from rotating inside the cap. I am currently trying out Redline CV2 (with their not moly moly) and will post back results when I have more time on it.
5. What is your favorite driveline set up? CV or regular u joint at each end?
I will echo Shawn here. Ideally you want to make things as simple as possible whenever possible. If you can make a simple two joint shaft work without issues then that is the ideal shaft. But it does not always work that way so you have to build what is necessary to make things work.
6. What is the worst mistake you have ever seen made with a driveline?
Too many to list but leave it to Alaskans to hack some crap together think it will work. One of my favorites was this guy was retubing shafts with old drill pipe from the oilfield. The Square tube shafts are a fan favorite as well.
7. What do you look for in a drive shaft build?
8. What else do we need to know about driveshafts and u- joints that we may be overlooking?
Too much to go into here in one thread.
9. Am I sexier than Blaine?
Not even gonna touch this one.
1. What is the biggest mistake owners make installing drive shafts?
Using improper or poor hardware. You need to make sure the strap, bolts and associated hardware are of good quality and working order. Commonly Ujoint straps are reused when ideally they no longer are properly retaining the joint cap and allow it to spin. Also making sure the fasteners are the correct length especially on double cardan shafts.
Also making sure to lubricate greaseable parts after installation. A lot of times folks do not make sure that things a properly lubricated prior to install so make sure to properly lubricate after.
2. What is the most common mistake installing u joints?
Being too rough and not maintaining cleanliness. I see a lot of yokes damaged by overzealous hammer use or the use of a ball joint press. Also not making sure to prevent contamination of the bearing and seal.
Lubrication. Not making sure greaseable parts are greased or adding excessive grease to non greaseable things like Spicer Life ujoints.
3. How often do shafts need serviced?
Shawn is absolutely correct on it depends on what parts are used and the conditions they are used in. General rule I recommend is regular greaseable ujoints under normal driving should be greased at 3500 miles or so. Hard off-road use or playing in the wet you grease after each run. And remember that you really cannot overgrease a ujoint. You need to make sure that clean grease is coming out all four caps to ensure that contaminates and the old grease has purged.
4. What kind of grease is best?
Spicer recommends Chevron Ultra Duty EP2 (or their fancy Calcium thickened synthetic) which is a good high temp red lithium grease. Ideally any quality high temp bearing grease used often will net good results. One thing to avoid is any grease with Moly in it as it has a tendency to keep the needles from rotating inside the cap. I am currently trying out Redline CV2 (with their not moly moly) and will post back results when I have more time on it.
5. What is your favorite driveline set up? CV or regular u joint at each end?
I will echo Shawn here. Ideally you want to make things as simple as possible whenever possible. If you can make a simple two joint shaft work without issues then that is the ideal shaft. But it does not always work that way so you have to build what is necessary to make things work.
6. What is the worst mistake you have ever seen made with a driveline?
Too many to list but leave it to Alaskans to hack some crap together think it will work. One of my favorites was this guy was retubing shafts with old drill pipe from the oilfield. The Square tube shafts are a fan favorite as well.
7. What do you look for in a drive shaft build?
8. What else do we need to know about driveshafts and u- joints that we may be overlooking?
Too much to go into here in one thread.
9. Am I sexier than Blaine?
Not even gonna touch this one.