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Front axle question

3K views 20 replies 10 participants last post by  lovsmud 
#1 ·
On the passenger side it has that little box where the axle is split, it has that fork with the little "gear coupling" or whatever it is inside there. I was wandering how that worked. Does it engage the passenger side wheel when you put it in 4x or what? If you can tell I know nothing about how it is supposed to work so all the info I can get will help.
 
#2 ·
That is called a Vaccum Disconnect. It has vacuum lines going to both the engine and the TCase. When you you put the Tcase in 4wd the vacuum created moves that shift fork over and engages the passenger side axle shaft.

This was not the brightest thing that Jeep had done with the YJ/XJ Dana 30 axles back in the 80's and early 90's. The vacuum lines can become brittle and break and then you lose it's function. A lot of guys go to a manual cable disconnect called a Posi-Lok.
 
#3 ·
So what is the best way to tell if it is working or not? I am not 100% sure but I think the last time I went offroad my passenger side did not seem like it was engaged.
 
#4 ·
jj33002 said:
So what is the best way to tell if it is working or not? I am not 100% sure but I think the last time I went offroad my passenger side did not seem like it was engaged.
That is the exact way you can tell if it's not working properly. :D
 
#6 ·
Check the vacum lines at the connections. Also there is a kit they sell that removes the vacum and give you a solid axle shaft vs the 2 pc one.
 
#8 ·
4x4 POSI-LOC in Quadratec $199.99

A little steep for essentially a brake cable from a 12speed bicycle, but it will work. There are write up on how to make Do-it-yourself posi-loc's with just that....12speed brake cable.
 
#9 ·
NY94YJ said:
4x4 POSI-LOC in Quadratec $199.99
Damn, it's been awhile since I put one of those on a YJ, but I would bet you can find them cheaper elsewhere.

If you need one give these guys a call here in Phoenix, I am sure they can do better than 200.

www.4wheelers.com
 
#11 ·
Since We're on front axles, I have a few questions.

1. How strong is the D30? Some people say it is fine and that they used to put it with a V8 on the CJs. Is it stronger than the D35? (apples and oranges, I know)

2. Has anyone installed solid shafts up front to get rid of that vacuum disco?

3. I've always wanted manual lockout hubs up front so I could run a locker and save my front end parts. Anyone know what all this takes?
 
#13 ·
yjswampthing said:
Since We're on front axles, I have a few questions.

1. How strong is the D30? Some people say it is fine and that they used to put it with a V8 on the CJs. Is it stronger than the D35? (apples and oranges, I know)

2. Has anyone installed solid shafts up front to get rid of that vacuum disco?

3. I've always wanted manual lockout hubs up front so I could run a locker and save my front end parts. Anyone know what all this takes?
Here are some answers to your questions.

1. Yes in a since it is stronger than the 35 rear. There's no C-Clip axles. The main difference is that the front axle sees considerably less force (Like 50% less) than the rear axle does. All of the forces are generally pushing on the rear. So you can get away with running more tire on the D30 without Ujoint and shaft failure. (Note, that doesn't mean you couldn't break it before you broke your 35. Everything can and will break.)

2. Yes, they do sell or can be easily made plates to seal up the disconnect and you can run TJ shafts in it.

3. Yeah, buy the Warn small hub (5x4.5) kit for like 900 bones and bingo you have locking hubs.
 
#14 ·
So if my vaccum isnt working does that mean that neither one of my front tires will pull in 4x4 or does it mean that just the passenger side wont work?
 
#15 ·
if you have a locker in the front than just the passenger side won't pull but if your front is open than you won't have any front wheel action
 
#16 ·
I dont really understand your answer, I have a stock front axle no upgrades or anything, when I put it in 4x4 should both tires turn or just one? If just one then which one?:confused:
 
#17 ·
the easiest way is to engage 4x4 mode and crawl under it with the tranny in nuetral and try to twist the front driveshaft if it moves than the front axel is not engaging
 
#19 ·
Well don't get too disheartenend. I was out muddin this weekend and thought something was weird. Sure enough, got it up on jack stands and my stupid disco isn't working. (You can tell if you put it in four and have a buddy or even yourself look under the car to see if the front driveshaft is spinning. When its off the ground, of course) Anyways I'm eventually gonna get solid shafts up there (tj style) but I think I"m gonna look into the cable shifter for now.
 
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