In addition to having a crummy tranny, I seem also to have a bad 4 wheel engagement system...in the '87 Wrangler apparently the 4 wheeling system is engaged by a vacuum on the front axle, but mine does'nt seem to be working..I have tried 4 wheeling small  hills and dirt mounds and it is all I can do to get over these hills without having to back down and try again...it should be almost NO CHALLENGE to get over them, but it isn't...anyone else had trouble with their vacuum 4 wheeling system and can offer some pointers/tips?

Mark

I have an 87 XJ myself. But no probs with that Vac setup yet but I expecting it in the near future. For 200$, there is a product out there called 4x4posi-lok. It eliminates all  Vac lines and all that garbage. I will be getting it soon. so check it out at  www.4wd.com   

You can pull the rubber vacuum line connectore from the disconnect on the axle.  Then apply a vacuum (grab one from the engine, or a "Mity-vac" to one side then the other.  You should hear the shift fork cycle one way and the other as you switch vacuum source back and forth.  You should also see the "4WD" dash light turn on and off (if you have one, not sure on oyur year).

Next, put the vacuum source back (on the engine, leave the axle one loose) and with the engine running, check for vacuum on the rummer connector you pulled from tha axle.  Only one should have vacuum.  Shift the transfer case to 2-hi if you were in 4WD or 4WD if yu were originally in 2Hi.  In other words, cycle between 2hi and 4 hi adn make sure your vacuum signal is switching from one port to the other.  If it is, you should be ok - just check for air-tightedness (?)  If not - you have either a disconnected vaccum line, or a bad vacuum switch onthe transfer case.  You need to have a good vacuum source to from the engine to the switch, and two from the switch to the axle.

get rid of the vac. actuator! Even if you find all of the vac. leaks you still may miss one. Just convert over to the manuel system. I just installed a 4x4 posi cable lock system in my jeep today, waiting for the rain to make mud, and the kit is simple. If you have a weekend to install it, and the know how, it is the only way to go. You are also able to get rid of all the vac lines and junk. I decide to switch it because I was tired of getting stuck in the mud and not being able to climb fairly small sand hills. The only down side is that the kit is designed to handel only up to 3 1/2 inches of lift, other wise, I like it!