1988 Comanche 4WD not engaging

[Manche Man]

Hello everyone, I'm newer to the forum but have used many of your threads as some solid guides to help out with my comanches.

I have seen many threads about this topic before, but none of them cover exactly what I need or want. With that being said, as the title states, my 4WD is not engaging.. Took it to the dunes the other day and noticed that the T-Case would engage but not the front axle. I narrowed it down to the shift fork not locking the axle into 4wd. I have seen many videos and tutorials/guides on how to do a CAD delete and just manually lock it in so it never fails again, but I have been told this also engages the running gear and will cause more friction and wear down the road (not to mention take my MPG down a notch or two). So, I'm guessing its the vacuum lines that aren't working, but I'm having a hard time finding where the lines go from the front axle. Anyone have any ideas where I might be having a leak/where the lines are going to?

Also, the jeep overheats when I put into 4 Low and drive it for a bit...

 

And before I forget, I have three 1988 jeep comanches, all 5 speed manuals, all 4.0 inline 6's, all relatively stock (bought them all used). The one I'm working on is a 1988 jeep comanche base model, 4.0, 5spd, AC/Heat, NP231 Command Trac transfer case, 153k miles.

 

 

Thanks guys.

[jdog]

My bet is the connector at the axle, and 95% of the responses are going to be lock it in, Chrysler did in the 90s and it doesn't affect mpg but a smidgen the only thing it will engage is the front drive shaft. If you really want to keep it a vacuum operating,  the lines go to the tcase and then to the firewall

[Manche Man]

51 minutes ago, jdog said:

My bet is the connector at the axle, and 95% of the responses are going to be lock it in, Chrysler did in the 90s and it doesn't affect mpg but a smidgen the only thing it will engage is the front drive shaft. If you really want to keep it a vacuum operating,  the lines go to the tcase and then to the firewall

Alright. So Chrysler did lock that front driveshaft eventually? Or did they find another method to engage/disengage it?

And do you know where those lines into the firewall go? Can I get to any if I pull my dash apart?

 

Thanks again.

[jdog]

Yes they went with a one piece axle shaft, iirc they go to the Vacuum ball in the bumper

[Manche Man]

Alright. Sounds good. I'll whip out the butane torch and see if I can find a vacuum leak somewhere.

 

I'll come back to this thread if I can't find it or have some trouble doing the CAD delete (shouldn't be a worry)

 

Thanks!

[Pete M]

the link in my signature has a couple ways to lock it for good. :) 

[Manche Man]

Alright! thanks! Probably will do the delete if I can't nail down those lines