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Thread: Cv vs u joint for axle shafts

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    Cv vs u joint for axle shafts

    Ok first off before you reply I'm ONLY looking for replies from people who have real world experience. Not people who read something online or their sisters, cousins, uncles, friends, brothers dad broke one. I've done lots of research online and cannot for an answer. Which is stronger a u joint or cv for an axle shaft? Now with a u joint there is binding when turning the wheel and a cv joint there isn't . I've now broken 2 driver side stub shafts while turning the wheel while trying to climb a rock. both times the ears failed and took the joint with it. Would I have broken if I had a cv? There wouldn't have been any binding. A u joint has 4 points of contact where a cv has 6 balls that are in contact. The only problem I see with the cv is the outer shell cracking. I know the cv boots are a concern as they rip easily which can cause premature failure. Now when jeep put v8's in the grands they used cv's which some say is because some are awd and this way it was a smoother drive but being that is is awd there is ALWAYS power going to the front shafts so if a u joint is stronger then why not use it? My jeep commander is awd and has a hemi. It is ifs and obviously has cv shafts in the front. I'm running a 3" lift in the front which is putting my cv's at a much greater angle when stock. I'm very hard on the commander and never had a failure. Now rcv are arguably the best axle shaft out there and they choose to use a cv joint. Mind you its much stronger then a typical cv but it's still a cv. So like I said if you have real world experience please chime in and educate me.
    Last edited by jthurstonjr; 10-20-2014 at 04:09 PM.
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    Quote Originally Posted by jthurstonjr View Post
    Ok first off before you reply I'm ONLY looking for replies from people who have real world experience. Not people who read something online or their sisters, cousins, uncles, friends, brothers dad broke one. I've done lots of research online and cannot for an answer. Which is stronger a u joint or cv for an axle shaft?
    Good luck...opinions are opinions regardless of if, when, or how the opinion relates to actual experience. That said, the answer to your question is not as simple as you would make it out to be. Those with CV's say they are stronger....those with U-joints say they are stronger. What we really need is destructive testing data for comparable components that gives us some type of quantifiable date to consider. I'm sure it is out there but I have not seen it.

    I see lots of people that switch to RCV's and praise their decision because they are so much stronger....than the stock u-joint stuff they replaced. Well, no shit. I would hope they would be stronger than OEM after dumping all that coin on them. If those aftermarket CV's were compared to the best aftermarket joints and shafts...then what? Then the answer becomes less than obvious.


    Quote Originally Posted by jthurstonjr View Post
    Now with a u joint there is binding when turning the wheel and a cv joint there isn't . I've now broken 2 driver side stub shafts while turning the wheel while trying to climb a rock. both times the ears failed and took the joint with it. Would I have broken if I had a cv? There wouldn't have been any binding.
    The claim is that the strength of the CV is constant throughout its range of motion where as a u-joint is not. On paper, that appears to play out but....in the real world, not so much. I can't speak for the D30/44 sized stuff but pretty much all of the RCV failures seem to have occurred when turning under large loads. So, take that for what it is worth.


    Quote Originally Posted by jthurstonjr View Post
    A u joint has 4 points of contact where a cv has 6 balls that are in contact.
    That sounds nice but you are comparing two completely different joint designs and not taking into account the total area of contact - only the number of contact points.


    Quote Originally Posted by jthurstonjr View Post
    The only problem I see with the cv is the outer shell cracking.
    I've seen pics of shattered RCV bells and inner races. I've watched Longfield Toyota bells and inner races explode. It can all fail just the same.


    Quote Originally Posted by jthurstonjr View Post
    Now when jeep put v8's in the grands they used cv's which some say is because some are awd and this way it was a smoother drive but being that is is awd there is ALWAYS power going to the front shafts so if a u joint is stronger then why not use it?
    You answered you question before you asked it. There is no question that a CV joint is the most appropriate joint to use in an AWD application. But that has nothing to do with the ultimate strength of the joint assembly.


    Quote Originally Posted by jthurstonjr View Post
    My jeep commander is awd and has a hemi. It is ifs and obviously has cv shafts in the front. I'm running a 3" lift in the front which is putting my cv's at a much greater angle when stock. I'm very hard on the commander and never had a failure.
    Put big rubber on it and lower gears and watch the parts fly. And if you really want to add insult to injury, lock the front. OEM CV's and axle shafts all have their limits...and the limits are...limited. lol


    Quote Originally Posted by jthurstonjr View Post
    Now rcv are arguably the best axle shaft out there and they choose to use a cv joint.
    Very arguably. There have been several high profile U4 teams and crazy bouncers that have switched to CTM joints and shafts from RCV. These are people that dealt with multiple RCV failures. CTM seems to have the market for the strongest of the strongest shafts and joints combined. The main problem with CTM is cost and lead time. They cost a fuk ton because they are made from billet 300M with rolled splines and proprietary after treatment and are all custom made to order. The cost is almost double for a complete front axle set from CTM as it is from RCV.

    I'm not saying RCV sucks. Far from it. They have clearly earned a well deserved reputation for stout shafts and joints. I'm just saying that U-joints are very far from obsolete and CV joints are still arguably NOT the absolute very strongest joint out there.
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    If knew you'd be the first to reply and was also hoping so. As for the commander I did put larger tires not that much but stock are 29" and I went to 32". It also has a elocker in the front and back from the factory.

    I can't help but look at all these factory truck (raptor and such) that all have cv shafts up front and wonder why they don't have failures consistantly. I think I might pick myself up a set of stock type cv shafts and run them for the first wheeling trip next year (while carrying spares as I usually do) and see what happens.

    I just can't figure out why no one has tested the difference between d30/44 shafts or at least shown their results if they have.

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    Quote Originally Posted by jthurstonjr View Post
    If knew you'd be the first to reply and was also hoping so. As for the commander I did put larger tires not that much but stock are 29" and I went to 32". It also has a elocker in the front and back from the factory.
    I would fully expect different results if your commander had something like 35's. I would not expect front axle components to survive - especially if it is locked up. It's not a whole different than a TJ or YJ in that regard - there are plenty of people out there that have great success wheeling with a stock D30 in the front with 32" tires. Start playing with bigger rubber and watch the components unravel.


    Quote Originally Posted by jthurstonjr View Post
    I can't help but look at all these factory truck (raptor and such) that all have cv shafts up front and wonder why they don't have failures consistantly.
    Your Raptor example is probably not a good one. There are tons of well documented CV and front shaft failures out there on Raptors - even running on stock tires. There is enough of demand for something better than the OEM CV assemblies that RCV even offers direct replacements.

    Beyond the Raptor, CV and front axle shaft failure is common among IFS vehicles that are actually wheeled. It is not as wide spread because so many IFS vehicles simply do not leave the pavement...regardless of how they are built or appear. My guess is that you don't see a lot of CV failures off roading because you probably don't wheel with very many vehicles that have them.


    Quote Originally Posted by jthurstonjr View Post
    I think I might pick myself up a set of stock type cv shafts and run them for the first wheeling trip next year (while carrying spares as I usually do) and see what happens.
    I'd be willing to bet that the OEM D30 CV's in Jeeps are probably at least as strong as their u-joint counterparts. I see no reason why they wouldn't be. The primary concern would be to make sure that the CV boots are perfect and water tight. Otherwise, they will not hold up well.


    Quote Originally Posted by jthurstonjr View Post
    I just can't figure out why no one has tested the difference between d30/44 shafts or at least shown their results if they have.
    Me neither. I would be interested in seeing the results. Though, as I suggested earlier, it might be difficult to quantify the differences with fair comparisons.

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    Well before I go and buy aftermarket shafts I'm going to get a passenger side cv (already have a driver side I've been keeping as a spare) and run them and see how they do. The shafts are the only thing that I haven't upgraded on my HP30. It's been tube sleeved, trussed, and locked. I'm running 4.10 gears and 35" tires.

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    You can take this for what it is worth but I would not suggest you spend another dime on your D30 if you plan on continuing to run 35's or larger. The last problem the D30 has is that the carrier is too small and correspondingly weak and this weakness cannot be addressed any other way other than to go to a larger axle. Axle shafts are a convenient fuse for a carrier that is too small.

    If you ever decide to go to something like larger chromoly shafts in the future, the shafts then become notably stronger than the carrier and you end up breaking the part that cannot be made any stronger than it already is.

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    I've blowen up a fair share of stock Toyota birfs which I consider CV axle shafts.

    The ifs cv is a different animal, and cannot be compared to solid axle cv shafts.

    The advantage CV has over U joint is even stated in the names. As both types of joint turn at an angle, CV's velocity stays constant, and u joints speed up and slow down. I would like to think this helps maintain traction in the rocks at slow speed.

    In an awd application this makes for smooth steering feedback on high traction Surfaces.

    I crack the outer bells on mine, and balls go boom making a huge mess. On an open knuckle app. this type of failure wouldn't wipe out trunion bearings, seal seats, etc.

    I have some TG dirty 30's cv's to try. Smaller balls, more material where it counts, better metal, bigger inner splines, etc. I will see if it solves my CV issues, but guaranteed it will move to my next weakest link which is R&P.

    Are CVs stronger? In the most extreme ends of aftermarket solutions for stock axle configurations for the extreme use, No. Are they better? Sometimes. IMO I would run them in a KOH type competition, but not in a rock bouncer type competition. Smooth, and efficient vs. brute strength.
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    I was breaking u-joints all the time in my Cj. I was running 35" BAJA Claws with a Lockrite locker. I tried stock ZJ cv joints. Broke them right away. Then I put in RCV joints, no more breaks. Even when I went to 37" tires I had no breakage. I was running a 5.2L V8 with an automatic. Now I must warn you, RCV joints are about $600 a side, but you will never break them.

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    [QUOTE=CJ5Steve;Now I must warn you, RCV joints are about $600 a side, but you will never break them.[/QUOTE]

    I like your brand confidence, but they can be broken. Well proven fact. If you treat them rite, and keep within there engineering limits your statement is true. Put some 40"+ tires on that theory, and bind them up in rocks with idiot style driving, and I'm not sure you would be as happy.

    Your stock replacement cv trial answers the OP's question perfectly. Jeep( or who ever did it) didn't make em stronger then stock unjointed shafts.

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    Quote Originally Posted by stickyken View Post
    I like your brand confidence, but they can be broken. Well proven fact.
    Yup. They make great parts...but they are time proven to be far from unbreakable...just like everything else.

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    Re: Cv vs u joint for axle shafts

    Quote Originally Posted by CJ5Steve View Post
    I was breaking u-joints all the time in my Cj. I was running 35" BAJA Claws with a Lockrite locker. I tried stock ZJ cv joints. Broke them right away. Then I put in RCV joints, no more breaks. Even when I went to 37" tires I had no breakage. I was running a 5.2L V8 with an automatic. Now I must warn you, RCV joints are about $600 a side, but you will never break them.
    Is this in a HP30?

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    Quote Originally Posted by CTD NUT View Post
    Yup. They make great parts...but they are time proven to be far from unbreakable...just like everything else.
    Local wheeler twisted the outer splines (30spl IIRC) on the D44 RCV's all to hell with a tired 4.0 and 36" Iroks. Very far from unbreakable.

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    Nothing wrong with either design as long as it's good parts. My Suzuki quad blew 2 aftermarket greasable u joints before getting the factory non - great able one. Because the u joint was drilled all the way through it was a lot weaker than a solid piece

    actually there is cv joint, u joint and the double u - joint cv shaft. My unimog had the double u joint front shafts
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    Here's my real world experience on my TJ.

    Running a D30LP and a lock-rite, never broke a stock u-joint. Just made sure they where always new and in good shape.

    Running a D30LP and a lock-rite, with stock Grand Cherokee V8 CV shafts - blew up on a regular basics.

    Running a D30HP with RCV\s - last year with 35s, this year with heavy beadlocks and heavy 35". Now blowing up R&P's. - Cracked a ring gear and then broke a cross pin. And I have a 2low kit in the t-case so most of the time offroad the front end doesn't even have power to it.

    So my lesson learned - somethings always gotta give - maybe it would be better for the $30 U-joint to fail then the ring and pinon.

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    Ever bust the carrier or just the r&p? With the HP30 I'm more worried about the carrier.

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    It very much depends on the carrier, though, your options will be limited if you step up to 30 spline shafts. Either way, expect the threshold for failure to be similar among the carrier and ring and pinion on an HP30.

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    I carried spare front shafts in my WJ because I could grenade the d30 CV shafts on que. Stock CV shafts are very weak IMHO. I never tossed a U-joint in my ZJ. both D30's with 33's.

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    Quote Originally Posted by CTD NUT View Post
    What we really need is destructive testing data for comparable components that gives us some type of quantifiable date to consider. I'm sure it is out there but I have not seen it.
    Let me add to this. Destructive testing would not just have to show yield and tensile strength, you would have to test numerous types of loading (shock, cycling, fatigue, high steering angle, low steering angle). And how does this testing change over the life of the product?

    There are a lot of variables to consider. If you magically find a way to run all this testing, I'm positive that the conclusion that you'll come to is that no one product excels at everything.
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    Quote Originally Posted by The_Hipster_Mario View Post
    Let me add to this. Destructive testing would not just have to show yield and tensile strength, you would have to test numerous types of loading (shock, cycling, fatigue, high steering angle, low steering angle). And how does this testing change over the life of the product?

    There are a lot of variables to consider. If you magically find a way to run all this testing, I'm positive that the conclusion that you'll come to is that no one product excels at everything.
    I'd settle for an ultimate and yield failure point of new parts in the straight and 45 degree angle. The upper echelon application of the very strongest parts are frequently in a position to fail with little to no wear. They are more likely to break from abuse before wear is likely to be considered a factor.

    Edit: Here is an Pirate older thread where there was some destructive testing of various shafts. There are a couple of companies that have the test equipment. A jig would need to be set up for the angular tests unless someone has already made one. I'm surprised we haven't seen more destructive test data emerge over the years.

    http://www.pirate4x4.com/forum/gener...axle-gear.html
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    I recall bobby long owning an axle breaking machine, and testing all competing cv products for Toyota cv's, including the d44 outer conversion shafts. That would answer some stuff. I don't have time to dig at the moment.

    Another advantage of u joints over cv is the fact the can steer sharper. Although, there is some hitech ifs stuff recently developed that can match, or beat u joints. But that's one-off, short-run, $$$$$ stuff.

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