Pete, to start with, vacuum is measured in inches/Hg, not pounds. I can't say for sure what the Koreans are up to, there. Generally, most of those systems use a hub that is full time, meaning they are always engaged, and the vacuum unit usually controls a disconnect in the front differential. This type of system means that the front hubs are engaged to the axles, but the axles are not engaged to the differential. When shifted to 4WD, either a manual lever or electric motor engages the front output shaft in the transfer case, and power is going to the differential, but it would be just spinnin' the driveshaft and ring and pinion in the diff, but no power to the wheels until the disconnect engages. On Dodges, this is done at the same time by a vacuum switch on the transfer case which ports vacuum to the disconnect when the lever is pulled into 4WD. Chevy used an electric shift solenoid on the front axle.
But, it sounds like on your system, you're shiftin' into 4WD, and engaging the front diff and at the same time, an electric solenoid is supposed to port vacuum to each hub and engage them.
1. An idling engine in good shape should have about 20 inches of vacuum. Anything about 17 would be fine.
2. Since you have engine vacuum on one side, but less on the other, you should suspect a blockage in either the line itself of possibly the solenoid valve.
3. With all 4 wheels off the ground, engage 4WD, and look underneath. Front driveshaft, differential, and axles should be turning. If only one wheel is turning up front, put a prybar under the spinning wheel, (against the ground), and stop it. If the hubs are engaged, the other wheel should immediately start turning. If not, disconnect the vac hose to the non-turning hub, and use the hose from the other side or a hand vacuum pump, and see if the hub engages. If it does, then disconnect the non-working hose from the solenoid and check for restriction. if ok, measure vacuum directly from solenoid. If not the same as the other side, there's your culprit.
4. If you dis-assemble a hub, clean thoroughly, and if the factory had used grease, apply a light coat to the parts. Generally, I used only a 90weight gear oil on those type of hubs, as grease can really slow them down or stop them from moving all together when it gets really cold. Also, if you do use grease, a very light synthetic would be better than a petroleum grease, as grease and rubber vacuum hoses or connectors do not play well with each other. Grease turns rubber into snot.
5. I am not working on this car over the internet!
One more thing, Pete. The front driveshaft has to be turning, (axles turning) for a hub to fully engage. You could check that also with a hand vacuum pump, applying to both hubs at the same time through the tee, and tuning the driveshaft by hand. Usually that way, only 1 front wheel would turn, then rotate the shaft in the opposite direction, and the other wheel would turn. I am not going to work on this car over the internet!
Damn it! I hate it when a Great Dane just got done drinkin' water and comes in and sticks his head right over my mouse hand. Friggin' slobber mouth!
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