Author Topic: 4WD Vacuum truobles  (Read 1671 times)

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Offline BlackhawkSX/4

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4WD Vacuum truobles
« on: March 01, 2013, 01:03:56 AM »
thanks fer lookin,

ok, in short- 4wd worked great before i had the engine rebuilt, and 2 years later (yes it took him almost 2 years) the 4wd does now work at all. i have looked at the diagrams and every thing on the eaglepedia and i still dont understand. i have no idea where the black tube from my vacuume can goes, or how it ties in to the red line. i have vacuume at the can and to the black hose but not at the red hose. every thing is plugged in and as it should be (as far as i can tell) i put it in the air, and the front tires dont do any thing.  i just want it to the stock specs, i dont want all time 4wd, or to start swaping parts with other cars. just back to working order.
id love to have a convo with someone who has been here before.

thanks again!
1972 Ford F250 Ranger XLT
1967 Ford F250 Ranger
1927 Ford Model A Rat rod
1982 AMC Eagle SX/4 Sport

Offline carnuck

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Re: 4WD Vacuum truobles
« Reply #1 on: March 01, 2013, 01:45:24 AM »
No swapping parts with other cars, but you can do a minor mod to the front axle so it stays engaged (but not in 4x4) See vacuum front axle mod in Eaglepedia.
   That makes it so you have a vacuum bottle, a line coming from the intake to it (make sure it wasn't plugged off first. Hooks in behind the carb on the intake), one from the bottle to the switch inside (should be center hose. You can test for vacuum there by unplugging from the switch and putting your finger over the hose end)
   The other 2 hoses on the switch are engage and disengage. (vacuum switches between the two for 4x4 and 2wd) These two hoses then only need to go to the vacuum "motor" on the tcase. Assuming it isn't rusted up from sitting (very common) there are 3 line fittings on it.
   The one closest to the linkage can be plugged for the bypass (if permanent I suggest siicone sealer and a vacuum cap) The one in the middle engages 4x4. The one on the end is to shift into 2wd. (I forget the proper colors, but it didn't matter at the time)
   This now makes your tcase shift on the fly except you need to remove the button on the 2wd to 4wd switch on the dash. The vacuum junk was realized by AMC/Jeep to be inferior and they did away with it after only a couple years. '85 to '88 are non-vacuum front axle. '80-early '81 as well.

If you're determined to pull your hair out and try to return it to stop and shift OEM, here's the diagram link:
« Last Edit: March 01, 2013, 01:47:48 AM by carnuck »
'87 Comanche 4.0L AW4/NP242 3.73 gears, lifted 5" on near new 33" tires $3500 obo
'82 Eagle Wagon (Brown Betty) 4.2L/727/NP229 and soon 8.25 rear axle and non-vacuum 3.08 front to match. 235/75/15 tires. It's down to minor body work (someone creamed my driver's door but I have another in good shape) almost rust free and interior work (seats are worn and carpet torn). $2000 but about to go up due to more work being done.

Pics of my other for sale stuff

Offline BenM

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Re: 4WD Vacuum truobles
« Reply #2 on: March 01, 2013, 04:47:18 PM »
The stop-and-shift has a lot of lines.

To begin, identify if you have a vacuum canister inside the driver's side fender. If it is there, that is the 4wd canister, not the one mounted to the fender in the engine compartment. All the accessories, 4wd, emissions, and heater valve, are supplied by the nipple on the intake between the runners for cylinder 5 and 6.

You may have up to three separate vacuum canisters involved.

There are metal lines under the car. These metal lines have three connectors. The center connector contains the red-yellow-green that go to the cabin switch.

The front connector, near the front axle, has four lines. One of those lines is where the vacuum source from the canister connects into the system. It should be rubber hose instead of vinyl line.

In 4wd you should be getting vacuum at the yellow line at the front axle.

In 2wd you should be getting vacuum at the green line at the transfer case.

You can pull the switch out to be sure the red line is getting vacuum to the switch and that the switch is operating correctly.

Once you have vacuum to each of those places based on switch position than the motors and traverse lines can be investigated.

1987 AMC Eagle Sedan -- 1976 Pacer Coupe -- 1968 Pontiac Tempest Custom S -- 1940 Mercury (& a 2002 Jetta Turbodiesel, 5 spd., the Wife's Daily Driver)


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