I've been discussing the vacuum to cable conversion for the front axle with some friends lately, and I'm most likely going to be doing it soon. We've been discussing, and I've been searching around trying to figure out weather there is in fact 2 vacuum motors that make up the 4wd system on the earlier XJ's(mines an 89). I have access to Alldata, and it seems like their diagram shows 2 vacuum shift motors. One in the axle of course, and one in the transfer case. I haven't been able to find any info regarding converting the one in the transfer case to cable if there is in fact one in there.

My understanding of the schematic is that when the lever is placed in 4wd, vacuum is sent to both shift motors. I'm assuming that the one in the transfer case connects the front driveshaft, and the one in the axle connects the front passenger side axle. Is this not how it works?

I'm considering welding the front diff on mine until I get different axles, and would still like 2wd low range. With the front welded(or locked with a locker) I would only have 2wd high range, 3wd low and high range or 4wd low and high range essentially.

If there is a vacuum motor inside the t-case, couldn't I do a cable conversion on that one as well? Couldn't I also just do a vacuum control solenoid on the vacuum input to the t-case, and be able to deactivate 4wd when the shifter is in the 4wd low position?

What do you all think?

 

Rustys solution

You can just cable lock the vac disco at the axle. What i did was use a hand vacuum pump to move it as i wanted and capped off the vac motor to lock it in place, only works if you have a good vac motor. later i just shimmed the collar fork over to lock it.

 

http://www.seriousoffroadproducts.co...ducts_id=76551

http://www.seriousoffroadproducts.co...ducts_id=76558

 

Thanks for the responses, but I already know all about the front axle disconnect. I was talking about a front driveline disconnect. If you lock the front diff, you can't get the 2wd low range option unless there is a way to not engage the front driveshaft out of the t-case.

 

What? no you cant disconnect the front driveshaft unless you remove it. If you had a d300 then yes but not with np231's.

 

Well that is what the first post was about. After looking at the vacuum diagram and schematic at alldata, it looks like there are two different vacuum shift motors. That makes me think that there is a disconnect assembly in the t-case as well as the axle. I don't know for sure if there is or not since I've never taken the t-case apart. I'm just going off of the information that is listed in the diagram.

I was hoping that someone who had taken one of this style t-cases apart before could shed some light on the subject. Diagrams(especialy from companies like alldata and mitchell) can be inaccurate at times, so you can't go off of just them. I haven't been able to find any other mention of a shift motor in the t-case anywhere else, so thats what may be happening here.

The diagram shows 3 devices. It shows a mode selector that sends vacuum to one port or the other on the shift motors, then an axle disconnect shift motor, and a t-case shift motor. Are there really 3 devices in the system?

 

Google is wonderful!!!

http://www.jeepforum.com/forum/f12/n...nstall-748821/

 

The one on the transfer case is a vacuum switch not a motor, when you pull the lever back it sends vacuum to the motor on the front axle. Or at least that's all there is or rather was on my '89. So not 3 just 2.

 

There is one moter that controls the collar in the front axle, the transfer case- when the lever is pulled it moves two forks in the case that move two gears that give power to the front, the shaft is always spinning because of the front wheels moving. The shaft spins a chain in the fad until u shift it then the power goes from the shaft in the case through the chain to the front drive shaft and if u have a good vacuum system the axle should be shifted over at that point and supplying power to the front wheels... u are likely to only spin one in muddy situations or when one wheel is off the ground because of the differential so that would be the reason to get a locker
Hope this helped a little, and this is based off of my 93 so I assume it would be the same

 

Thanks guys, I have seen the writeup on the other forum already. It doesn't go into a huge amount of detail about whats going on with the vacuum system. You can see the connector, but not much else. I have a feeling that there is in fact only two motors. You can see where the confusion would come in. This is the Alldata schematic of the 4wd vacuum system:

 

There were a few early years that had a transfer case that had only three positions, Hi N Lo. They then had a switch on the center console to switch between 2wd and 4wd, I would bet that's where that schematic is coming from.

I believe that it was NP207 from 84-87? Either way after 88 and later would not have the motor on the transfer case (Would be manually shifted with lever) and one vacuum motor on the front diff.

 

That makes sense. In one of the other pictures, it shows a bracket for the mode selector that looks like it would go in the dash. Thats a perfect example of why you can't rely on Alldata and Mitchell for accurate information all the time.