D30 Vacuum Disco Eliminator

I got an '89 4.0

my D30 is vac. disco. I want to eliminate the vac. portion.

The 2 ways i know of are tack weld the sliding ring at the "Engaged" position, or get the non disco shaft and slide that in.

Right now i believe i will just go the cheapo way and tach weld the ring.

Also i have a question about the vac. disco, When the 2 line plug is plugged in my "Part time" light is on but when i unplug it from the vacuum module the light goes out.

could this be caused by a weak diaphragm that is not disengaging the sliding ring?

thanks,

PJ

The vacuum is switched at the transfer case, to the vacuum motor on the disconnect.

The vacuum motor slides one way or the other depending on what side the vacuum is delivered to. The 4WD light does not indicate true motor position, but the presence of a vacuum in the engage side line. No vacuum on the engage side, or a severe vacuum leak = No 4WD light.

u can unhook and plug off the vac lines and take off the vac motor flip it upside down, slide the collar over, put the motor back on upsided down, that way u dont have to tack it and can un do it later if u want

Some people also use nuts/washers to keep the fork in the "engaged" position.

so what side is the ring on when it is engaged

Slides to the driver's side to engage the 4WD light switch.

You could just get the cast iron fork (the aluminum one tends to hairline crack and bend under pressure, causing it to have the light on, but no 4WD) from the posi-loc system and a new shift motor from Rock Auto. I paid 72.00 for the motor shipped and it came 2 days on a saturday and 50 from summit.com for the fork.

I have had problems with my disco system for 6 years before I just shelled the clam for the fork and motor. Works fine if its maintained. Check the vacuum hose next to the battery if you have weak vacuum. Mine now functions like it was meant to, regardless of hammering on the throttle (low vacuum condition). Always stays engaged when I need it to.

It will work if you have proper vacuum, a strong fork and a strong vacuum motor.

thicky said:

u can unhook and plug off the vac lines and take off the vac motor flip it upside down, slide the collar over, put the motor back on upsided down, that way u dont have to tack it and can un do it later if u want

Click to expand...

Never heard of this one, what do you mean flip the vac motor. Do you mean the diaphram? Either way I just used washers to space out the fork so its engaged all the time until I get done welding up my non disco D30.

I did my 88 XJ using this method towards the bottom of the page in this link.
http://www.comancheclub.com/forums/viewtopic.php?f=7&t=2001&start=30

Took all of about 15 mins to do.

I bought a 200.00 POSI-LOCK for my disco and works great cable operation smooth and reliable

I've read that you can take the disco off and remove the clip that holds the fork, slide the fork over and reinstall the clip making it full time. I'll look for the link.

*EDIT* Found it.
http://www.jeepforum.com/forum/f12/vacuum-disconnect-locked-dana-30-cheap-way-788543/

jbsjunk said:

I've read that you can take the disco off and remove the clip that holds the fork, slide the fork over and reinstall the clip making it full time. I'll look for the link.

Click to expand...

That is correct.

I did this on my 87 MJ and it worked great. Simple, free, fast, effective. I don't know why anyone does anything else.

Some other takes on it: http://www.jpmagazine.com/techartic...154_0904_dana_30_vacume_disconnect/index.html