Couple of questions I'm seeking some advise on.
1. I have a 93 YJ, while off-roading last weekend, my 4 wheel drive was failing to disengage when shift back into 2 wheel. I finally checked up front and sure enough the there was still suction on the vacuum even though it was out of the 4 shift spot. I finally just had to leave it disconnected to unlock the front. Has anyone else had this same problem? I've heard that these vacuum pump systems being unreliable, I'm considering switching to something like a posi-lock or something else if somebody has some better ideas???

2. I've had my alignment checked and tires balanced and I still can't get rid of a steering wheel shake at about 35-45 miles per hour. My tires are 33x16, I know it's a rougher ride with larger tires, but man this is killing me. Anyone have any ideas there?

As I said in the subject I'm not the best mechanic, I've put on a 3.5 lift and replaced the headers, both of which I had some help on but that's about the toughest things I've done so far, so hoping to find some simple solutions.
Thanks  

What kind of steering wheel shake are you talking about here? Is it pretty bad and front end shakes or a mild vibration?  

I would call it pretty bad. Shakes the steering wheel and the whole vehicle pretty good.  

Okay, you have caster death wooble. It is cause by a combo of caster and toe in setting. With oversized tires, factory alignment spec do not always work. You might start by checking the toe in yourself and see what it is set at and also the lift may have changed the caster angle but that is not hard to correct with shims on that model jeep.  

took it to my local tire place, they seemed to have got the toe and caster thing fixed. Not shaking anymore. Thanks