4wd vacuum + Front axle

[TommyW]

does anyone know wher the main source of vacuum is for the 4wd system. I know it comes from a switch on the transfer case, but I want to know where it comes from before that. I am replacing broken, worn, tore, ripped, basically bad vacuum lines and i want to be sure to get that one.

	Transfer Case Mounted behind and driven by the vehicle transmission, the transfer case transmits power to the front and rear driveshafts in 4WD Jeep vehicles and offers high and low range.

[TommyW]

I have and 86 cherokee, with the stupid vacuum disconnect, and i was wondering if anyone knew what other axle would fit. When i was at the junk yard the other day, i saw a ton of other cherokees without the front axle disconnect vacuum cr*p, and was wonding if any of them would bolt right up, without having to do major mods or regearing anything.

	Front Axle Disconnect A mechanical or vacuum-operated component used primarily on four-wheel-drive models to connect and disconnect drive torque to the front axle. When shifting from four-wheel drive to two-wheel drive, this system disengages the front axle from the front driveline, so that the front wheels aren't turning the front driveline unnecessarily. This reduces unnecessary front driveline wear, noise and fuel consumption.

[Tug-n-pull]

If you are in the process of front axel vacumme line replacement do your self a favor and pitch the vacumme all together and try this. You are sure to be glad you did!
http://home.earthlink.net/~stevenschreiber/cabledis.htm tug

[Tug-n-pull]

Hey tommy see your other post on vadumme! tug

[XJNick]

<Merged Threads>

Hi,

The source vacuum for the 4x4 system comes through the RED vacuum hose. This hoses receives manifold vacuum from a line that comes from the vacuum reservoir. The red line connects at "Tee" which is located next to the Charcoal Canister (by the coolant reservoir).

-Nick

[XJNick]

Instead of replacing the axle which is costly and time consuming, follow the link that Tug has provided above. This home-made manual 4x4 system is very easy to make!

-Nick

[TommyW]

I have already made a cable operated system, however ended up breaking the fork within a week, so i went back to the vacuum for the time being.

For my home mead system, i cut the vacuum motor off at the bell part and put a rubber cap over that end so as not to get water in or let gear oil out. I drilled a hole in the other end, in line with the actuating rod, and drilled and tapped the rod to accept a 1/4" threaded cable. Made up a bracket for the cable, routed it to the inside, and had a cable disconnect.
Worked ok, for a couple of days, but as I said before, I ended up breaking the fork and was stuck without 4wd (for 1/2 hour, while i switched back to vacuum). Oh, i plugged the line that puts it in 2wd, and joined together the one that puts it in 4wd to the one going to the light switch, so when i put the transfer case in 4wd, the light lit. If anyone wants pictures, let me know and I will e-mail them, broken fork and all.

	Transfer Case Mounted behind and driven by the vehicle transmission, the transfer case transmits power to the front and rear driveshafts in 4WD Jeep vehicles and offers high and low range.

[Bounty__Hunter]

You can always put a TJ axle shaft in the passenger side, or a shaft from a non-disconnect XJ. You have to change one axle seal to a different size and cap off the disconnect area.

I like the vacuum system, works good once you mess with it and understand it. Can be a little finicky in the cold.

[TommyW]

a couple quick questions,

is the vacuum diagram the same for the 86,

when i accelerate or put a load on the engine, my 4wd light goes off and sometimes the front axle shifts out of 4wd, where should i look, besides the lines going to the actuator ( i have so far replaced almose every vacuum line that i have seen)

can i tap the red line into a vacuum source coming from the manifold (would this give me better continuous vacuum) under load

[XJNick]

First of all, a loss of vacuum upon acceleration is a direct result of a vacuum leak in any part of the vacuum system.

can i tap the red line into a vacuum source coming from the manifold (would this give me better continuous vacuum) under load

The answer to this question is YES, and it would work. However, you then are bypassing the vacuum reservoir and check valve. This means that it will probably work WORSE than it would if connected normally through the vacuum reservoir.

Basically, you need to find and fix that vacuum leak. Here's a question: Does the heater/A/C air blow out of the defrost vents when it is not supposed to during acceleration? If so, it is most likely a leak in the manifold vacuum lines.

-Nick

[TommyW]

Yep, it switches from heat to defrost when i accelerate or put a load on the engine, never noticed it until now.

I have changed every vacuum line that i have seen, but am unsure about one thing. The vacuum canister behind the front bumper has only two lines going to it, one a vacuum source and the other going into the cab. it kinda looks like it could have two more plugs on the side towards the center of the jeep, but there is nothing going there and no caps either, is it supposed to be this way ?

Also, i was thinking of simply adding another vacuum canister just for the 4wd system. Would tee off of manifold vacuum with a check valve to the canister and then just the one line going to the 4wd system from that cnaister. Any comments on this idea ?

[XJNick]

Hi,

The vacuum reservoir has 4 connection points, two on each side. They should all be connected to something or plugged.

-Nick

[TommyW]

i finally fixed my 4wd, turned out it was a vacuum line for the heater/defroster control. Also, found out the vacuum canister has 2 sides to it, and they are seperate, so if there is a leak on one side, doesnt effect the other side, guess thats why there was nothing connected to the other side on mine, and it wasnt plugged, it didnt need to be

[XJNick]

I didn't know that. Always assumed it was one reservoir. Cool.

-Nick