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D-30 disco to D-30 non disco swap, questions?

xjtrailrider

xjtrailrider

NAXJA Forum User
NAXJA Member
Location
Roanoke VA
Yep i searched and all I got was "Sorry".

I'm getting ready to swap in a non-disco D-30 into the front of my 90 XJ that currently has a disco D-30.

For those that have done the swap; What did you do with the vacuum lines going to the old axle? How/where did you plug the lines?

I want my "part time" light to still work on the dash

TIA
 
The vacuum diaphragm on the axle hits a switch which lights up the 4WD light on your dash. If you remove the diaphragm, you won't have the light. Later models that came with the non-disco D30 had the switch for this in the t-case, so that the shift rail engaged the switch for the light.

I just screwed some bolts into the vacuum lines. Can't remember where the lines originate...
 
MoparManiac said:
The vacuum diaphragm on the axle hits a switch which lights up the 4WD light on your dash. If you remove the diaphragm, you won't have the light. Later models that came with the non-disco D30 had the switch for this in the t-case, so that the shift rail engaged the switch for the light.

I just screwed some bolts into the vacuum lines. Can't remember where the lines originate...
Click to expand...


Thanks

The lines originate under the coolant reservoir. I wonder what I can rig up to make the light work.
 
I think you can just use the non-vacuum transfercase switch from the 92+ model.

EDIT: rockauto.com shows the NP231 electrical switch 95+, so that may be the one you need.
 
Last edited:
Look for the red plastic line from under the passenger side of the engine, near the fire wall. This is the vacuum feed to the transfer case. It tees into the vacuum line from the manifold. Just remove the tee, and join the lines together.
 
You could leave all the vacuum lines intact from the res, to the tcase, to the switch under the coolant bottle. Then your light would still be vacuum actuated.

Just plug the yellow and green on their way down to the axle.

Kind of a dumb way to do it, you're just asking for vacuum leaks, but I'm sure it would work.

Robert
 
joe_peters said:
I think you can just use the non-vacuum transfercase switch from the 92+ model.

EDIT: rockauto.com shows the NP231 electrical switch 95+, so that may be the one you need.
Click to expand...

Would you not have to use the whole transfercase?

The switch is located at the top front portion of the case. I don't remember a provision being there in the 91- cases with the disco 30.

WrenchMonkey said:
You could leave all the vacuum lines intact from the res, to the tcase, to the switch under the coolant bottle. Then your light would still be vacuum actuated.

Just plug the yellow and green on their way down to the axle.

Kind of a dumb way to do it, you're just asking for vacuum leaks, but I'm sure it would work.

Robert
Click to expand...

The switch is actually contacted down at the vacuum diaphragm IIRC? What are you referring to when you say the switch under the coolant reservoir?
 
Nope, nothing electrical in the axle.

There's a short branch line off the "lock" vacuum line that runs to a diaphragm-actuated switch under the coolant bottle.

That switch turns on the light...

Like I said, it'd be a long, ugly way to do it, but it ahould work.

Robert
 
You sure?

I had two wires running from the vacuum diaphragm up to the engine compartment.

It's been a few years now so I don't remember where they went. Pretty sure they had to do with the 4x4 light.
 
Here is a link to the Posi-Lok install, just use the electric switch off the later models on the transfer case and run the wires up to and tap in the same place where the Posi-Lok switch does on the firewall.
 
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