Center axle disconnect

Dalko43

Explorer
Reading up on the 4th gen ram 2500/3500, I learned that the 4x4 system switched from locking hubs to a system known as CAD (center axle disconnect). I believe the changeover year was 2013. I have a vague understanding of how it works.

Does anyone here know how it compares to the locking hubs in terms of reliability, robustness and ease of repair? I know that ram pickups used a similar system in the late 90's and early 2000's and had some issues with the vacuum lines that operated the system. I haven't heard of too many issues with this newer system (which is either electronically or mechanically controlled by a borg warner unit depending on the trim level you get). Anyways, just wanted to see what thoughts people had on this setup.


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Bennyhana

Adventurer
I haven't heard a whole lot from people having maintenance issues with the current CAD. But, i do think it's a weak spot in the drivetrain. Ram claims it's to aid in fuel mileage but it's just one of those over-engineered add ons that makes things more complicated than need be. I had a 94 chevy that I added a posi-loc kit to make the CAD like manual hubs. It was a cable actuated solenoid so I could choose to leave it open and run in 2lo. Wondering if that would be an option to look into with this current system? Then there's the Dynatrac hub kit....$$$$$$
 

Buliwyf

Viking with a Hammer
It's rubbish. Dodge screwed up big time when they switched to it. More of a response to GM's marketing "You can select 4wd without getting out". Which is something you can do with old Fords and Dodges anyways. We just leave our hubs locked in on snowy weeks.

That being said, it's fairly reliable and easy enough to service. Just a shame. Manual hubs are far superior IMO.

At first I thought it was silly because they could steal more Ford customers if they had manual hubs. But I guess the weirdo GM people too lazy to turn a hub closed out number the Ford people they want to attract.
 

1stDeuce

Explorer
Alternate view...

Reading up on the 4th gen ram 2500/3500, I learned that the 4x4 system switched from locking hubs to a system known as CAD (center axle disconnect). I believe the changeover year was 2013. I have a vague understanding of how it works.
First, Dodge hasn't had locking hubs on ANY pickup since 1993. From 1994 till 2002, ALL dodge trucks used CAD.
From 2003 to 2012, the 2500/3500 trucks didn't use any disconnect at all, meaning the entire front driveline was always spinning, even in 2wd.

It appears that they brought CAD back on the 2500/3500's for 2013+. I'm sure this was to gain a bit of mileage, if only a few tenths.

In my experience, there's nothing wrong with the CAD systems that Dodge is currently using. Sure, back in the early 90's, the CAD actuation systems were less than reliable as trucks got older, but newer systems are holding up fine even after hundreds of thousands of miles. I have 240k miles on my 06 GMC that uses the same style electric actuator (If not the SAME actuator) as the new Ram trucks, and it gets shifted a lot more than most. It's original, and still working perfectly.

I will admit that there is ONE way to have issues with any CAD or even Ford's auto hubs for that matter... If you wait to engage 4wd until you are stuck, the splines may only partially engage when you try to drive away the first time. If you find yourself stuck in 2wd, and needing 4wd to continue, pull the lever or push the button, then gently apply some throttle in drive, then in reverse, then back to drive. This allows the CAD to fully seat the splines on the slip collar, or the hubs to fully engage, and you can hammer on it to your heart's content. My personal suggestion is that you shift to 4wd as soon as you even think it might be needed. This ensures full engagement of the front axle by the time you really need it. (This was not a concern on the trucks with no CAD, or on Fords driven with the hubs locked all the time.)

With CAD vs traditional locking hubs, your axle shafts are still spinning, but the differential and driveshaft are not. The differential spider and side gear also spin, but there's no load on any of the spinning parts, so it would take millions of miles to actually get any appreciable wear. In my experience, it keeps the u-joints better lubricated. Seals may eventually wear out, but they went out on my old trucks with hubs much sooner, so I believe having them always spinning seems to work better than having the whole front end sit still for the better part of a year.

My opinion is that you have nothing to worry about. Just try to be a little preemptive with your engagement of 4wd, and wave at Buliwyf when you drive by while he's out in the snow locking his hubs, only to find out that one is frozen, or his u-joints have rusted up over the summer... :)
 

Dalko43

Explorer
First, Dodge hasn't had locking hubs on ANY pickup since 1993. From 1994 till 2002, ALL dodge trucks used CAD.
From 2003 to 2012, the 2500/3500 trucks didn't use any disconnect at all, meaning the entire front driveline was always spinning, even in 2wd.

It appears that they brought CAD back on the 250.
? I know there were locking hub kits for the rams 2003-2012 rams. What kind of system was in place prior to 2013?


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Mundo4x4Casa

West slope, N. Ser. Nev.
I have the 2001.5 Dodge 2500 4WD version of the CAD. The CAD went 160K miles with only occasional woes, like the actuator wire and vacuum tube pulled off by brush passing underneath. It only disconnects the longer side of the front axle with a sliding sleeve, and at that only about half of it, so the rest of the drivetrain from the T-case forward is still turning. In my view a useless solution with approaching zero gain in mpg or handling. But, I did a work around discussed at length in this article:
http://truckcamperadventure.com/2017/01/extreme-truck-camper-drivetrain-build/
Here is a pic of my Dana 70, 35 spine outer stub shafts:


I now have a defacto Dana 70 front axle in a Dana 60 housing. A plus that I can see with the Dana 70 outer stub shafts and MM Dana 70 free wheeling hubs is the possible use of low range 2WD: oh, and any traction aiding device in the pig made for transparency in 2WD.
One thing to note is with a rig this heavy there is very little mpg or acceleration gain by disconnecting all running gear north of the transfer case. With my smaller rigs, in the past, hubs or no hubs did made a small difference in mpg. The biggest gain was loosing the Unit Bearing assy, famously unrepairable, and only there because it saved Mopar 11 cents and of ease of installation at the factory. Same can be said with the ball joint assy vs. Ford's King Pins for the Dana 60.
I suspect you can do the same thing with the AAM axles, which are a tad bit more heavy duty is some respects, like a few more splines and a few hundreths of an inch larger in axle shaft diameter. The housings are kind of a wash, strength wise, IMHO with the AAM hanging closer to the ground.
The kit I used to upgrade the Dana 60 front end works with the AAM front end by adding a shim.
 
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NevadaLover

Forking Icehole
It's rubbish. Dodge screwed up big time when they switched to it. More of a response to GM's marketing "You can select 4wd without getting out". Which is something you can do with old Fords and Dodges anyways. We just leave our hubs locked in on snowy weeks.

That being said, it's fairly reliable and easy enough to service. Just a shame. Manual hubs are far superior IMO.

At first I thought it was silly because they could steal more Ford customers if they had manual hubs. But I guess the weirdo GM people too lazy to turn a hub closed out number the Ford people they want to attract.
Spoken like a lifetime koolaid slurper!! as if fords plastic locking hubs or vacuum system is superior to dodge or gm systems!! manual hubs used to be superior but now they are plastic, can't tell you how many f350's we have in the fleet that have been downed by hub failure, keep a set in stock because of these garbage systems that ford designs and sells to people too stupid to look at and understand that just because it looks like old school locking hubs it doesn't mean they work the same!
 

Buliwyf

Viking with a Hammer
Mine are manual. No auto vacuum or nothing. Never failed, never will, pretty sure they're metal, Warn, LOL. It's a 10 min job to pull them and lube them. You can upgrade to the next better Warn hub in 30 minutes for little cost last time I checked, if you really have an issue with the plastic.

Can't do that with a Dodge or GM. Your stuck with whatever they give you. How much does it cost to get manual Hubs and a one piece axle on a Dodge? $1740.
https://www.youtube.com/watch?v=xy3ALzLYhjg
$1800-2300:
https://www.dynatrac.com/free-spin-kits/dodge-truck.html
That's enough to make me consider a truck that cost more but has manual hubs stock. Likely another $1000 in labor for people that aren't mechanical enough to tear the Dodge front axles down. Anyone that can eat pudding without choking on the spoon can replace the hubs on a Ford.

It's worth noting, that the hub acts as a fuse as well. Still it's an easy fix for any knucklehead. How can you not love manual hubs? Do you really want your front end spinning and wearing all the time?

Don't call me a cool aid drinker. I've owned all 3 trucks, and know which ones I liked best. Put your ego away. It's a forum, expect differing opinions and experience. If you want to start name calling, go back to Pirate 4x4 where that $%^& belongs.


$350, and you don't even need to get a jack out. (my seat covers cost more than that)

https://www.youtube.com/watch?v=GoZRzIQZy3E

https://www.youtube.com/watch?v=NggS7N5S7SI
 
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NevadaLover

Forking Icehole
But I guess the weirdo GM people too lazy to turn a hub closed out number the Ford people they want to attract.
Don't call me a cool aid drinker. I've owned all 3 trucks, and know which ones I liked best. Put your ego away. It's a forum, expect differing opinions and experience. If you want to start name calling, go back to Pirate 4x4 where that $%^& belongs.

Hypocrite much??
 

Dalko43

Explorer
So moral of the story is with CAD vs locking hubs each have their pro's and con's. And the modern CAD used by Ram seems to be a bit more reliable than the older vacuum-operated version.

That about sum it up?
 

TeamDoty

Cpt. TeamDoty
I had a 1991 Jeep Cherokee (Chrysler/Dodge era) XJ chassis. They had a CAD of sorts on the passenger side of the front axle. It became highly unreliable but there was a cheap solution. Your mileage may vary on your Ram but here's what a lot of Jeepers did... there was an "inspection hole" or some unused bolt on the outside of the maintenance cover. We replaced that bolt with a longer bolt and machined down the threads at the end so it would extend into the shift collar thus holding it permanently in the engaged position. I think the mode/shift fork was removed for this too. Anyway, it was a cheap, dirt simple way of keeping that axle connected full time. Later I spent the $$$ on a Posi-Lock cable kit to allow me manual actuation of the collar. I did this after going to a full mechanical locker in the front to aid in tighter turning radii on certain trails. Just throwing this out there - you might find a way to lock it into the full time mode without much more than a $1 bolt :)
 

NevadaLover

Forking Icehole
So moral of the story is with CAD vs locking hubs each have their pro's and con's. And the modern CAD used by Ram seems to be a bit more reliable than the older vacuum-operated version.

That about sum it up?
Absolutely! Most of these systems work for a long time with no problems, some people have more trouble than others but for the most part they all work well!
Some people just can't stand any system that their favorite brand does not use and will go out of their way to point out the flaws while ignoring the flaws in their favorite system!
Usually there will be a fix or work-around for any flaw in your system if one shows up, so run what ya got and enjoy it!
 

Buliwyf

Viking with a Hammer
And then there's shmucks that'll stand up for any system that's on their favorite trucks even if it's completely stupid and useless. Even if it means a newb getting stuck somewhere when his actuator fails. If noone tells Dodge to do better, they won't. Marketing get's to tick the boxes marked "don't have to get out to engage 4wd" and "lightweight steering in 2wd".

Dodge had it right with the Gen1 trucks. It would be nice to see a manual Super 60 under the front of a modern Dodge.
 
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