CAD/Disconnect Debate: Why Not..lets have em.

John Fuller

John Fuller

XJ Fanatic!!
Banned
Joined
Jan 3, 2015
Location
Boone NC
because of so many many negative comments on these axles, thought i would start a debate to really find some facts/truth/personal experiences with these axles from all different types of wheelers!!!

ok so i know i'm fixing to start a huge ordeal/debate on the CAD topic BUT WHY NOT: why does everyone hate them so much?? the splines on the axles are HUGE and will never brake, the u joint is the same size as the rest of them, technically speaking 2 smaller shafts same diameter as one long shaft is stronger and harder to break, and the supposed to be "weak" link Collar is only weak when the CAD fails and does not engage/disengage all the way (ask me how i know lol) I've ran the D30 Disco on 9 jeeps and only one ever broke collar cause i didn't fix the engagement system and "thought" it was good but all the others including my current 88 xj with it are replaced and hooked up to strong vacuum that i know and control and never had a problem. i've broken many ujoints on these axles from turning all the way while spinning too much but the collar that everyone says is the weak link has only failed on me and customers (including the ford truck customers) when the CAD doesn't engage/disengage properly so i really think people should highly reconcider their "tests" on these axles. Last but not least point to make about the Disco axles is the housing: the housing is lot more durable than regular D30s or whatever uses the CAD because of the extra big collar they put there so not as high a chance to bend the axle tubes and not so much need for Gussets. I realize this post is going to start some major bashing but i just never could understand the hate on these but also feel if they are properly maintained and properly used (properly being emphasized here), they are no weaker but rather very possibly bit stronger than regular. Every customer with jeep or mostly fords that come to me with broken collars is cause they tell me they "always" engage on the fly or while rolling and they hear a pop and 4wd quits working...go figure.
another point as explained to me long ago: take 4ft 2x4 wood brake it in half. ok good. take those 2ft pieces and exert the same force on them to brake in half again....won't happen with same force applied because of the shorter length of the same rigidness mathematically requires more force applied to brake the 2ft pieces. The CAD axles themselves are very similar in this same application...2 smaller axles which have bigger splines and ends are a lot harder to break than one double the length shaft same diameter. i probably didn't explain this as good as a friend did to me long ago but i think i've made the case good enough.
 
Your 2x4 reference is incorrect. Usually a shorter axle breaks first because it lacks the ability to twist and absorb the shock that it trying to break it.

I think most people do away with it simply to have fewer parts that could possibly fail.
 
Dana 30 CAD axles use the 260x Spicer joint (except for the 95 YJ which used the 297x joint) and those are known to be very weak. Most do away with the CAD in order to use the bigger/stronger 297x/760x joint equipped TJ and XJ shafts. In addition, the use of CAD introduces more moving parts and additional items to fail.

More splines is better than bigger splines. The more splines you have, the amount of torque carried by each one is less.

Want a "good" budget Dana 30? Use a non CAD XJ HP30, take the stock 297x joint shafts and grind them to accept full circle clips. Install new Spicer 760x joints and you have a solid axle for cheap.
 
strange1 said:
Your 2x4 reference is incorrect. Usually a shorter axle breaks first because it lacks the ability to twist and absorb the shock that it trying to break it.

I think most people do away with it simply to have fewer parts that could possibly fail.
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well that's new info to me..so the longer shafts can actually "twist" to absorb the shocks of torque applied to them?
 
Jody Treadway said:
More splines is better than bigger splines. The more splines you have, the amount of torque carried by each one is less.
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now this is something i've never understood or had explained to me. i guess i always thought the huge splines would handle more torque than little ones but this explanation you put suppose makes sense.
i guess in the end, i've always liked the CAD and Still Do LOL, just cause for guys like me it's a easy cheap free locker that is street friendly. i've been told that there are ways to put the bigger joints on these cad axles but still haven't figured it out yet from research...suppose too that since i'm much easier on my CADs that they serve me better than others and just keep it away from full steer when getting on it.
 
Jody Treadway said:
take the stock 297x joint shafts and grind them to accept full circle clips. Install new Spicer 760x joints and you have a solid axle for cheap.
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this? but thats using the non cad axle isn't it. i'd like to stay using the CAD i have until someday upgrading to someting worth upgrading to but wouldn't hurt putting stronger joints in it i guess. i already bought the HD joints for this one which held up good last weekend
 
Jody pretty much summed up why I swapped a nondisco shaft in my 90xj...bigger joint and less moving parts means more reliability. I never snapped a front shaft, but have broken front ujoints, so the bigger ujoints was the selling feature. It helped that I already had the shafts, just needed to get an extra seal.
 
I broke my d30 several times, first with 33's, then again with 36's.

With 33's the axle shaft on the pass side between the side gear and the CAD broke right at the end of the side gear.

With 36's the ears on inner driverside side shaft ujoint quit. The ujoint didn't break, the ears removed from the shaft.

This was a small ujoint 1990 yj axle that was open, with 4.56s.

Had a posilock cable on the CAD, and broke several shift forks. The vacuum actuator would never last longer than 6 months.
 
Mac5005 said:
I broke my d30 several times, first with 33's, then again with 36's.

With 33's the axle shaft on the pass side between the side gear and the CAD broke right at the end of the side gear.

With 36's the ears on inner driverside side shaft ujoint quit. The ujoint didn't break, the ears removed from the shaft.

This was a small ujoint 1990 yj axle that was open, with 4.56s.

Had a posilock cable on the CAD, and broke several shift forks. The vacuum actuator would never last longer than 6 months.
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point taken and the usual common carnage posts lol. i still like them for their cheap locker street friendly uses for now. when i get the money to upgrade my front diff...it will be straight to 60 so till then, i will manage.
 
John Fuller said:
lol if i knew what a birfield was!!! what is it though...
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Look up RCV Performance. It is a strong joint made to replace the u joint. The origin of the birfield can be commonly found in toyota & samurai.
 
John Fuller said:
well that's new info to me..so the longer shafts can actually "twist" to absorb the shocks of torque applied to them?
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Even chromo shafts are only surface hardened. This twist is why you commonly see shafts broken in multiple locations. Also why you see twisted splines on the shafts, just outside the carrier contact patch.
John Fuller said:
now this is something i've never understood or had explained to me. i guess i always thought the huge splines would handle more torque than little ones but this explanation you put suppose makes sense.
i guess in the end, i've always liked the CAD and Still Do LOL, just cause for guys like me it's a easy cheap free locker that is street friendly. i've been told that there are ways to put the bigger joints on these cad axles but still haven't figured it out yet from research...suppose too that since i'm much easier on my CADs that they serve me better than others and just keep it away from full steer when getting on it.
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While the larger diameter does give alot of strength to a shaft, there are other things at play here. The coarser splines create more force/pressure on each tooth. Also how the shafts are machined, there are several locations that create stress risers & weakness.


I would say that unless you're planning to go bigger in tire size, you can beef up the hp30 to handle it under mild wheeling.
 
paradisePWoffrd said:
I would say that unless you're planning to go bigger in tire size, you can beef up the hp30 to handle it under mild wheeling.
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lots of real good info here..thanks guys. my dream XJ if i would call it that or my current setup will eventually be 60s front and rear with 38s/39s max which with my wheeling style and desires...should be able to handle more than enough abuse from anything i would ever throw at it. i'll never be the rock crawlin type guy(for most part) so my jeep on 60s and 38s would suit me very well for what i like to do. i would however still put in a doubler just because for those times i would want to play on some rocks.
 
I'm not sure if this ever happens but swapping the CAD for one piece shafts causes the front driveshaft to spin and might cause vibrations from unbalanced front driveshafts that came from the factory on some years.
 
Tradarcher said:
I'm not sure if this ever happens but swapping the CAD for one piece shafts causes the front driveshaft to spin and might cause vibrations from unbalanced front driveshafts that came from the factory on some years.
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yes it does but half the XJ front DS are balanced and the others aren't..i got lucky and mine was but i also have 3 spares that are all balanced too. funny how i've had soooo many front and rear DS spares and never had to use one..but front axles is what i don't have any spares for so i always invest in HD joints for those and just leave the DS alone lol
 
strange1 said:
Your 2x4 reference is incorrect. Usually a shorter axle breaks first because it lacks the ability to twist and absorb the shock that it trying to break it.

I think most people do away with it simply to have fewer parts that could possibly fail.
Click to expand...

I have had the opposite experience with my Samurai. I have broken three shafts, and all of them were the long side. One front chromo shaft, and two stock rear shafts(samurai rearend is offset).
 
drkelly said:
I have had the opposite experience with my Samurai. I have broken three shafts, and all of them were the long side. One front chromo shaft, and two stock rear shafts(samurai rearend is offset).
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i agree and know people who have broken longer shafts but not the disco ones but i guess like anything else in this world, there's a story to everything from one side to the other. reminds me of all the people who have broken D35 shafts/rears on 31s doing hardly nothing but others (like me) have abused em with 40s or current 35s and hold up just fine...i think in the end it's just a human made error since humans cannot build anything perfect consistently. some get the good stuff others get the great stuff. Ford Explorers got their name for a reason but i've again, met people with original 300K+ miles on ALL original stuff never an issue that they expected to have. ohh well, that's life!!
 
When an axle breaks, it's always the one with the most traction regardless of length. All things being equal, a longer shaft will twist a degree or two more than an equally built shaft of a shorter length before snapping.

I doubt if that's really ever an issue for a CAD dana30, as most will break at the 260x u-joint first.
 
yep...i've only ever broken the Pass side joint for some reason..beats me but it does when one goes, but i've never put in heavy duty joints and properly installed so that plays a big roll too. now ive gotten the trick down pretty good for getting them in smooth as silk and turn nice and freely.
 
Been wheelin my '95yj with 33s and a lock right for 17 years: CAD still works like a charm. Just finished a weekend trip to Big Dogs at the Cove, the old YJ continues to impress.
 
^^^i agree. they work awesome when kept up with and maintained. i also have notice with the last 3 of mine, when the carrier is welded/locked it engages a LOT smoother too...i guess with it being locked the splines are always lined up where the collar is cause with open diff i almost always could hear it slightly (on quiet surroundings) engage but with last 3 welded, i never hear it and instantly engages...maybe it's just me but seems that way.
 
http://4x4posi-lok.com/adv.html
Has anyone considered using this cable control instead of relying on vacuum? Is the fork in the diff the problem or is it merely the victim of a not so healthy vacuum system? But to be honest, if the vacuum actuator system was so great to begin with, then why was it so short lived on some platforms?
 
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