$30 posi lock have you tried this

[law.74]

...law 7.4...I HAVE this done on my comanche, and NO you cannot shift at "moderate speeds" without grinding. my wheels spin at the same speed, and the only time i can shift is below 10mph. this is because my assembly is running off of engine vacuum. the engine produces more vacuum than the t-case, and so it wants to force the actuator over...whereas the t-case actually slowly pushes the actuator.

YES I could. I also used engine vac. The t-case doesn't generate vac. it just switches engine vac. It is possible it is "restricted" I suppose.
YMMV... moving on...

 

[jeepcomj]

YES I could. I also used engine vac. The t-case doesn't generate vac. it just switches engine vac. It is possible it is "restricted" I suppose.
YMMV... moving on...

disagree.

the transfercase generates vacuum. in no way does it connect to engine vacuum whatsoever. the entire vacuum harness for the CAD is connected from t-case to axle, with vent tubes going up to the passenger side of the firewall. there's no vacuum supplied from the engine to the transfercase (I've done 4 CAD 4wd swaps and not one have I had to connect the vacuum hoses to the engine...just put them in, and go once the rest of the 4wd hardware is installed)

i know what mine is capable of doing...shifting at speed is not something it does. however, I am supplying my air through 1/8" ID hardline so it IS getting more vacuum than it would from the factory 1/16" ID hardline

 

[law.74]

the transfercase generates vacuum. in no way does it connect to engine vacuum whatsoever. the entire vacuum harness for the CAD is connected from t-case to axle, with vent tubes going up to the passenger side of the firewall. there's no vacuum supplied from the engine to the transfercase

Interesting. First of all what T-case are you using?
Assuming you're referring to the 231... I see no way for the case to "generate vac". How does it do this? There is no vacuum generator. There is a perfectly good vac generator under the hood (ie the engine)

Here is a diagram from an '88 FSM (this applies to '84-'90) vac systems. The check valve at the top right of the image connects to engine vac. Those "vent tubes" are actually one single vent, and the other is a check valve that is (should be) connected to engine vac.

I'm truly curious how you were able to avoid engine vac. I must confess, however, I've never worked on an MJ. If they are really that different from XJs, YJs etc. from the same vintage then feel free to enlighten us. My experience with these cases is limited to '90 CAD and '00 non-disco NP231s.

Please post back with more information

 

[jeepcomj]

I see no indication of connection to the motor in the diagram.

as for vacuum, I truly do not understand how a transfercase could create vacuum, BUT all of my systems have worked without connecting them to engine vac.

riddle me that one?

 

[law.74]

I see no indication of connection to the motor in the diagram.

The check valve on the top right as previously stated. It doesn't have to state that it connects to the engine because, at least in '88, mechanics knew what check valves were and more importantly what they do.

as for vacuum, I truly do not understand how a transfercase could create vacuum...

Nor do I... hence this whole conversation