Vacuum lines/4wd ok? Continued

I am going to assume that my 4wd is not working- although maybe someone needs to explain what "part-time" really means. I assume if the rear tires slip- the front tires engage? How long can that take?

I ran a simple vacuum test and found that one of the vacuum lines (the yellow line) to the transfer case had vacuum pressure while the tuck was idling in 4H. The other two lines (I think green and blue) had nothing. Is that normal that? IE pressure is only applied to those lines when it is moving???

The lines to the front axle were basically the same- one of the three were functioning in an idle state.

TIA-PRL

If you got vacuum then take the actuator motor off. Sometimes the fork that slides inside there is broken which can be replaced without buying a new motor. In my case, the rubber peice that the two vacuum lines are molded to had oil from the oil filter drip down on it and deteriorated so it was pretty loose (this is where the lines go to the axle). When you take off the motor, if you see rust and/or dirt stuck in there then you gotta either clean it out really good or buy a new motor (aboout $80) and replace the vacuum lines going to the axle.

And when in 4wd both the front and rear wheels are driving the jeep not when rear slip front engages.

Dean

Yes- I had oil and grime all over my rubber fitting on the axle. I degreased it- but it still does not feel like a tight fit.

By actuator motor- do you mean the one that is at the front of the air filter box?

Sounds like you have a Dana 30 disconnect front axle. This axle has a disconnect mechanism on the passenger side of the differential. There is a vacuum motor to move a fork and collar to disconnect the passenger side axle from the diff.

Just to clarify, "part time" means that you should only use it part of the time, not that it engages only part of the time. "Part time" 4WD locks the two axles together without any slip between them, making it unsuitable for dry pavement, where you need a way to allow the two axles to uncouple on turns. Part time 4WD is an unsophisticated system and has no speed sensors, internal viscous clutches, differentials, etc.

If everything in a Dana 30 disconnect axle is working, it should engage 4WD immediately. If the dash light goes on, it usually means that the axle is engaging properly. When it is in 2WD, there should be vacuum to one side of the vacuum motor on the axle, and in 4WD there should be vacuum to the other, whether moving or not. The third line on the vacuum motor supplies vacuum to the switch that operates the dash light. The vacuum lines that run beneath the battery are a common source of leakage, as is the vacuum reservoir that is hidden behind the bumper on the passenger side. If the fitting on the vacuum motor is rotten and you can't find a replacement, you can remove it and use regular vacuum hose, but of course you'll need to remember which line is which.

If you can, you should test the vacuum motor itself for leakage. If it's all right and the lines are good and you're still not getting engagement, it could be the vacuum switch on the transfer case. That switch is not very expensive.

Rather than fool with the whole vacumn operated mess I just installed the Posi-Lok cable actuator on mine last week. Took maybe 1.5 hr and was pokeing around doing it probably could do one in an hr easily. For 160 bucks I now will never have to fool with it again I hope..... vs $50 for the replacement lines at the axle and maybe the actuator $80 and then theres the lines at the tcase and the tcase switch if they go bad. Plus now if I ever need it I have the option of 2wd low.
http://www.4x4posi-lok.com/
http://www.collinsbrosjeep.com/main.htm
Mike B.