How to fix the vacuum motor on your YJ

[Chris]

First of all, I want to give credit where it's due. I followed Coyote_94YJ's direction's except that I used a nylon spacer instead of the spring.


I've done this install a couple of times now. First on my old YJ and second on my Dodge Ram last weekend. It is a simple process and it costs very little.

Here's how you do it.

1) Remove the 4 bolts that secure the shift motor to the axle housing and remove the shift housing assembly(careful some 90wt will pour out so have a drip pan handy).

2) Remove the 2 "E" type retaining clips that hold the shift fork on vacuum motor and the 1 "E" type retaining clip that holds the vacuum motor to the shift housing.

3) Pull the vacuum motor out of the shift housing which will slide the shift fork off the shaft.

4) Take the shift motor to the hardware store.

5) Buy a long spring that is just large enough to slide over the shaft of the vacuum motor shaft and take it home.

6) Slide the spring onto the shaft of the vacuum motor, put the shift fork back inside the shift housing and slide the vacuum motor back inside the housing so as to fully compress the spring. The spring will be too long so make a rough guess as to how much to trim off so that the vacuum motor will go all the way back into the shift housing.

7) Once the spring is the correct length slide the vacuum motor back in and install just the 1 large "E" type retaining clip that holds the vacuum motor into the shift housing. The other 2 are no longer needed. (Yay, left overs)

8) Slide the shift collar inside the axle housing over to engage the front axle.

9) Reinstall the shift housing back on the axle housing making sure to align the shift fork up with the center of the shift collar inside the axle housing. Also be sure to add a bit of RTV gasket maker to prevent leaks.

10) Top up the fluild level in the front diff, and go for a test drive to make sure it works.

Now for the pics. Please excuse the quality. I took them with my mobile.

Here is a pic before removing the shift motor. I used a 1/2" socket to remove the 4 bolts. Then I unhooked the switch wire and the vacuum line.

This is a pic of the collar in the disconnected position. Make sure that when you reinstall the shift motor that the collar is slid all of the way toward the drivers side.

Here are a couple of pics of the housing and fork before disassembly. Note the position of the fork. It CAN be installed backwards :whistling:. More on this later.

Here it is disassembled

Here it is reassembled with the fork on backwards. I had to take it apart and flip the fork over, but I didn't get a pic of it turned the right way. Also, notice the nylon spacer on the shaft. This is where the spring should be if you choose to use one.

I hope this can be a help to someone.

 

[Flyer58]

First of all, I want to give credit where it's due. I followed Coyote_94YJ's direction's except that I used a nylon spacer instead of the spring.

Chris, I just finished with the rear axle and now it's time to start on the front. In trying to solve my lack of 4WD I found all my vacuum lines were separated at the multiple connectors and the transfer case switch was full of gunk. I got all the lines connected and switch cleaned out so now the vacuum system tests and works as it should but still no 4WD. The NP231j was out during the rebuild, I put new seals in and it works properly. The only thing left is the front vacuum motor has failed.

So my question is - by adding the spring or nylon spacer does that keep the front axle halves engaged all the time as opposed to the motor engaging and separating them? I'm ok with that, I guess the 4WD light will stay on and MPG may vary.

Thanks.

 

[Flyer58]

Well almost 5 months later and 30 degrees cooler I finally got around to locking the front axle using a similar method as the OP.

This was probably the original piece and the first, and only, bit of trouble I had was separating the vacuum motor from the shift housing. The two were frozen together. I ended up removing the position switch and drifting the shift rod out from the other end.

I purchased a nylon spacer from Home Depot (65 cents) and the fit is as close to perfect as you can get. It's not a thick spacer but there's no real forces against it as it just keeps the fork from sliding out of position. When installed the fork has about one millimeter or less of play yet keeps the sliding locking collar centered where it needs to be.

Very easy job and now I need to track down an electric switch for the NP231 - TJ style and wire it into the circuit.

Also made sure to plug the vacuum line from the intake manifold.

Here's a few new pictures to include the spacer I used.

Cheers.