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vacum disconnect + and - 's


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I’ve heard about the vacuum disconnect on axles, but never paid any attention to that topic until now.

 

When I went to make my axle upgrade appointment, they asked if my D30 had one… They said they could “take the disconnect off and simply cap it off with a plate”. So I did some searching/reading and understand the BASICS of what that all means, but what I don’t understand is: what is the benefits and downfall of doing that…?

 

If I just removed it wouldn’t my axle be stuck in 4x mode? I saw a cable mechanism replacement in one of my many aftermarket catalogs, wouldn’t that be the best way to go? :help:

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Your transfercase shifter is what shifts you into 4wd. The purpose of the CAD was to keep the front driveshaft from spinning when the truck is in 2wd (in a feeble attempt to save gas, which is doesn't). The CAD has no benefit for most of us.

There's no need to fab up a plate. Just pop off the cover, pull the little C-clip, slide the shift fork and collar over to the "engaged" position, and then re-insert the C-clip to keep it there, then reattach the cover and start capping vacuum lines. :thumbsup:

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If you have a spool, and you actuate the disco with a cable (posi lock), you can use it to lock/unlock your axle, kind of like a selectable locker. I have an Aussie locker in the front, planning on doing something like that for 4wd winter driving, but ended up converting to a single piece shaft and block off plate after the vacuum lines got snagged and pulled off on a trail for the third time.

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They make a plate/seal kit?

 

I just cut a piece of 1/4 steel I had laying around, drilled 4 holes for the screws and used some RTV. One of my 297/760 shafts came out of a Cherokee, the other one out of a Grand.

warn sent it with the hub kit when i put it on my tj a hundred years ago... i didnt need it for the tj and kept it for some reason..

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There are a couple of ways to eliminate the axle disconnect, and if you're having this done on your truck it would be a good idea to clarify up front exactly what "they" are giving you for your money.

 

(1) The simple, quick-and-dirty way is to remove the vacuum shift mechanism, slide the collar (it works just like a synchro collar in a manual transmission) over to the engaged (or "locked") position, fix it in that position either by shimming with washers, moving the 'C' clip, or even putting a hose clamp on it -- then reinstall. The two-piece axle then remains permenently engaged.

 

(2) Remove axle disconnect mechanism, remove inner and outer axle shafts, and replace with one-piece axle shaft. This requires finding or making an inner seal for the right side of the differential housing, because with the CAD the seal is located outboard of the disconnect. The downside to this is that the seal may be a special seal, which could be difficult to find if it needs replacement. (It can be even more difficult to find if you don't know what it is.)

 

(3) Variation on #2, same procedure but replace with newer year axle shaft that has the larger U-joint at the outer end. This obviously also requires replacing the stub shaft that goes in the hub/bearing unit.

 

Approaches 2 and 3 eliminate the CAD entirely, so they would call for a blank cover plate to replace the vacuum motor mounting plate.

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anyone use the rok lock? sp?

it uses a vernier cable to engage/disengage the collar.

 

i have a similar type CAD axle on my dodge (dana 60) diesel that i put a vacuum switch on so i have 2 low when needed. great for low range 2wd.

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I did #3, and did have a problem finding the seal mentioned in #2. After first buying a stock non-disconnect axle seal and finding out it didn't fit I researched the internet, and ordered one from NAPA. I was down for a few days tracking down what might work, and waiting for it to arrive, but well worth it. Single piece shafts with the larger joints are a LOT easier to find than 2 piece ones (95 YJ only, I believe). No more vacuum lines pulled off on the trail, and no more broken u joints.

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Somebody on NAXJA several years ago (might have been Woody, one of the former presidents) IIRC did a single shaft replacement for the CAD and actually used a Dremel to hog out the inner end of the axle tube so he could use the same seal as the driver's side. There's a LOT to be said for using the "correct" part, but it takes a brave man to do that machining with a Dremel. (Although I suppose if you set the seal with enough goop around the outer diameter, the goop will compensate for a bit of gap-itis around the bore of the axle tube.)

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  • 3 years later...

I did #3, and did have a problem finding the seal mentioned in #2. After first buying a stock non-disconnect axle seal and finding out it didn't fit I researched the internet, and ordered one from NAPA. I was down for a few days tracking down what might work, and waiting for it to arrive, but well worth it. Single piece shafts with the larger joints are a LOT easier to find than 2 piece ones (95 YJ only, I believe). No more vacuum lines pulled off on the trail, and no more broken u joints.

I know this is a few years old,  but do you have a part # for  the seal?

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NOS (Napa Oil Seal) 11800.

Was that seal used by the carrier or in the vacuum housing?

 

I've been searing forums through naxja and stu's offroad and come up with seal numbers:   

 

NOS11800 
 
**NOS 11343
 
NOS11777
 
**  2x  NOS 11771 
 
NOS 18050
 
Some are refering to an inner and out seal like the warn kits.  One referenced using two 11771's   most seem to reference 11343 as the one at the differential.   
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I didnt spend money on a block off plate or bother with the hasle of making one.

Didnt cut the fork either, just put the cover back on. The fork is quite a bit larger than the axle shaft so why bother...

Didnt remove the bearing either, probably should have, but oh well...

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WAY over-complicating locking the d30 in the locked position.  Simply remove the disconnect, slide the shift collar over both axleshafts, and install the disconnect upside down.  Holds the axleshafts locked together perfectly.

 

I run a manual disconnect and a spool in my front d44, and before that a manual disconnect in my Lincoln Locked d30.  They don't make a spool for the d30 but they should LOL.

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AY over-complicating locking the d30 in the locked position.  Simply remove the disconnect, slide the shift collar over both axleshafts, and install the disconnect upside down.  Holds the axleshafts locked together perfectly.

 

I run a manual disconnect and a spool in my front d44, and before that a manual disconnect in my Lincoln Locked d30.  They don't make a spool for the d30 but they should LOL.

 

 

:agree:

 

Just use the write-up I did awhile back that I linked to on page one and is now in the DIY section, here is a link even. CAD fix

 

 

I have the posi loc so the locking  is not the issue.  I'm not worried about eliminating the CAD because of the possible broken shaft replacement difficulties.  It's 1000 time easier to locate and swap a single shaft.   When I go out with people they carry spares for their rigs and if someone gets in a bind we all help each other.  Last trip 2 people popped u-joints and had to replace shafts, I've yet to damage mine but right now i'm the only one with the cad split shaft.     So it's more getting the rig in a more swappable scenario.  

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