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So, how strong are the disco D30s? considering keeping it, got some ?s

Mr. Ninja

NAXJA Forum User
Location
Issaquah
Alright so i've got a disco D30 front in my 1990 xj. The vacuum system is going tits up (go figure) and I'm trying to figure out what way to go to get it operational in a reliable fashion. Here's what I'm thinking:

The idea of keeping the disco front axle is kind of appealing for a few reasons: for one I could convert to a cable posi-lock system and virtually not have to worry about the damn vac system anymore, doing this would effectively give me the option of having a pseudo 2Lo, which would be kind of cool. Also I could put a locker in the front and use the disco so it'd still drive ok on the street and not be locked up unless I want it to be. This is my daily driver. So I guess what I'm really wondering is how strong are the disco axles/shafts/etc. Can I upgrade to the later style 297? u joints to gain the strength of doing a solid shaft swap using newer axles? Is this just retarded?

At this point, with this being my daily driver, I don't plan on scaling rock walls and shit everyday, but when I take it out on the weekends i'll probably beat on it a little bit. But mainly it will be to get to a destination back in the woods. I'm running 33's, non-HO, ax15, np231. Mainly I'd like things to be stout enough that I won't be blowing shit up everytime i put it in 4wd and have a little fun. I'm no stranger to trail fixes and wrenching/whatever, but if its goint to be a major pain in the ass to fix broken shafts on the trail then I'm not to keen on that.

Down the road I'll be doing bigger/stronger axles, but there's alot left to build before then.
 
I went the posi lock route with my swapped in disco 30 thinking the 2lo would be beneficial. I found it less than ideal to engage/disengage on the fly as you have to be moving at the right speed to really get it to go in.
 
I went the posi lock route with my swapped in disco 30 thinking the 2lo would be beneficial. I found it less than ideal to engage/disengage on the fly as you have to be moving at the right speed to really get it to go in.
 
Islander: once it was in did it seem to work fairly flawlessly?

I guess the idea of 2Lo is kind of a neat idea rather than the main reason I'm considering keeping it disco. I think the idea of a locker in the front that wouldn't affect street driving qualities would be more along the lines of why I'd keep it disco.

builder: I understand that the newer U-joints are stronger. can they be made to fit the disco axles? Are the actual shafts much stronger? I can see why a one piece shaft would probably have less weak points than a 3 piece shaft, but realistically what are we talking in differences in strength?
 
...I could put a locker in the front and use the disco so it'd still drive ok on the street and not be locked up unless I want it to be... Can I upgrade to the later style 297? u joints to gain the strength of doing a solid shaft swap using newer axles?

On the road, in 2wd, it won't make much difference. With no input torque, the locker unlocks.

Offroad, in 4wd, it's really nice to be able to unlock the axle and turn so much tighter. I love it.

For strength, you can upgrade to shafts from a 95 YJ, gain the 297 and keep the disco.

Or, you can swap in any one-piece shaft to eliminate the disco, by installing a new seal in the axle... Search, it's been covered...

Robert
 
Islander: once it was in did it seem to work fairly flawlessly?

I guess the idea of 2Lo is kind of a neat idea rather than the main reason I'm considering keeping it disco. I think the idea of a locker in the front that wouldn't affect street driving qualities would be more along the lines of why I'd keep it disco.

builder: I understand that the newer U-joints are stronger. can they be made to fit the disco axles? Are the actual shafts much stronger? I can see why a one piece shaft would probably have less weak points than a 3 piece shaft, but realistically what are we talking in differences in strength?

Yeah, once engaged stayed in just fine, but it seemed that I would need to back up to really get it to dis-engage.

I run 1pc shafts now with an Aussie Locker. Other than some noise you don't notice it in 2wd on the street.
 
We put a disco & Posi-Lok in my kids' 95 with AX-15 & he loves it. It's a cheapo alternative to locking hubs & lets him run a locker. You have to finesse it to shift on the fly, but it can be done, carefully. If you can shift a np205 on the fly, or shift a motorcycle clutchless you'll be able to do it easily. ABS & all 95 YJs have the 297 U-joints but I don't believe there are any alloy axles for a disco. Guys with YJs regularly run 35" tires with no problems, but I wouldn't run anything bigger than a 33" myself. Locking hubs & a super 30 would be better of course, but that is way too much work & money to put in a 30.
 
Alright, this sounds like it'll be a decent option. Although I'm thinking I probably won't bother with a locker, and maybe just go with a spool or welded diff, since i'll be able to unlock it and there isn't any point in spending the money on a locker then. Don't really plan on going bigger than 33's anytime soon, and when I do, I'll likely go with different axles then.

Haven't heard of anybody snapping the disco part of the d30 yet, so I think I'll be ok.

Any other input from anyone?
 
I'm working on a way to shift the front disco (CAD) with a "push/pull" air valve in the cab eliminating the cables and broken shifter forks. The plumbing I need to tap into is just below the center console at the T-case so this will be a easy upgrade and should work just fine for connecting and dis-connecting the front.

I plan on mounting the air valve inside of the center console and using it to switch vacuum on/off to the actuator.

I'll let everyone know how it works when i get around to it this winter.
 
I'll let everyone know how it works when i get around to it this winter.

It works great, I've been running it almost two years now.

The only problem I've had was when the front axle drooped enough to unplug the vacuum lines from the disco box. I bent the hardline down a couple inches, ziptied the vacuum plug in place, and haven't had a problem since.

Also, the valve I used was too big for the console, I had to put it in the kick panel, where the hood release used to be.

And you might as well pull your "supply" vacuum off the canister up front, and eliminate eight or ten feet of leaks-waiting-to-happen...

Robert

Edit:
airvalvethumb.jpg

mandisco1040.jpg
 
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