converting to shift on the fly

[jim]

We have been hijacking anrkii's classified post long enough so I started this thread.
When converting to shift on the fly you have fewer vacuum lines.  After you lock the front axle you can remove everything to the front axle.  You keep those lines from the switch to the transfer case.  I don't remember the details but someone will chime in here.  It may be necessary to plug something.
You can remove the pull down knob on the dashboard switch.

[carnuck]

Pull knob is just a circlip. The tcase hoses are simplified. I'll post a pic of the fitting that gets plugged (unless you are lucky like me and have a non-vac front axle one already with only 2 ports). Essentially the tcase motor has 1 line that engages 4x4 when applied, then the dash switch is changed and the other gets vacuum, disconnecting it.
   3 lines on the switch: One to vac motor disconnect side, middle to vacuum source (ball under hood, which is hooked to intake vacuum) and other to vacuum engage port on tcase motor. That's it! All that's needed once the front axle is engaged for on the fly shifting.

[captspillane]

Putting the hose clamp keeps the fork from moving freely once you disconnect the vacuum. This is the most important step. If you just disconnect the vacuum it will do damage to your axle or your viscous coupler or both.

I also eliminate the vacuum motor at the transfer case and pull tension on that shifter to make the Eagle true All Wheel Drive like they were designed to be.

[Eagle1984]

Also how would I know if my 1984 Sedan is shift on the fly, does it have a fixed front axle, I know there are vacuum houses going to the front but those would for the T-case correct.

[ammachine390]

Also how would I know if my 1984 Sedan is shift on the fly, does it have a fixed front axle, I know there are vacuum houses going to the front but those would for the T-case correct.

Provided the interior 2wd/4wd switch hasn't been changed over the years, there will be a pin and markings that say STOP, PULL, ENGAGE if its stop and shift. If it is shift on the fly, there will be no pin.

[Eagle1984]

Also how would I know if my 1984 Sedan is shift on the fly, does it have a fixed front axle, I know there are vacuum houses going to the front but those would for the T-case correct.

Provided the interior 2wd/4wd switch hasn't been changed over the years, there will be a pin and markings that say STOP, PULL, ENGAGE if its stop and shift. If it is shift on the fly, there will be no pin.

There is no pin. I thought I read somewhere that 84's still had the none fixed axle.

[carnuck]

Nope. My '83 has the vac axle. NP119 cars and post '85 are non-vac. (though not a hard and fast rule. POs also change stuff)

[Eagle1984]

Thanks, just wondering after you have taken the cover off how do you add more fluid to it? Do you have to take that part/shaft of the front axle completely off?

Also just in theory if you guy had the choice between the NP 119 or NP 129 which one would you take, taking in the speed difference of course of putting it on a car that originally had the NP 129, just in theory of course.

[captspillane]

Try putting a ramp under the passenger side of the Eagle and leave the driver side on the ground. No fluid will come out as you pull the cover. You simply remove the four bolts, pry gently to pop free of the old gasket material, clean up the gasket surfaces, put a hose clamp on the shaft of the shifter, and then reinstall it with RTV gasket maker. There are two little bushings at the tip of the fork that you should try to keep from popping off and losing. When you put the cover back on make sure the fork slides into the groove of the coupler and that it is still there with the coupler all the way outboard as you finish tightening the bolts.

I drive my Eagles as All Wheel Drive vehicles. My NP129 versions have rope replacing the shift mechanism to keep them in AWD permaneantly, identical to the 119. The 2WD isn't at all necessary in these cars. The nice thing about the 129 is the possibility of mechanical failure. If I need to tow on a tow dolly I just crawl under and pop it into 2WD. If the front axle needs to be removed temporarily I just put in outer halves of CV shafts to keep the wheel bearings intact and then put it into 2WD.

As far as my choice of transfer case, the only one I'm installing in my Eagles is the NP242. I use the original driveshaft with a piece of pipe installed to limit the travel of the original slip joint. I have pictures of this in my project thread.

The 242 has 2WD for towing or repair situations. It has an open differential perfect for driving the Eagle in AWD. It has a fully locked position for totally snow covered or otherwise extreme conditions. It has a low range perfect for slow moving utility.

The 242 does not have a viscous coupler. Don't fear this. Subaru all wheel drive and just about every other AWD vehicle are open differential transfer cases, including 1986 Eagles with the 128 case. The VC has extremely little impact on vehicle performance. The only time it matters is when you're stuck in mud, and even then it doesn't perform nearly as well as the fully locked position of a part time case.

A 242 performs better in nearly every way, the only downside is that it requires owner input. The 129 was meant to work well, not great, but to do so automatically without any input from the driver.

I also tried rebuilding a NP 129. I was disgusted to see how poorly the VC is designed. The vast majority of 129's on the road do not have working couplers and the owners just think it is doing something. They fixed that with the NP249, but at the expense of reliability. In a 249 the Coupler must work or the vehicle has to be towed. The 119/129/229 coupler is much less robust than the 249 coupler but it doesn't matter because it forms a donut around an open differential. It's more decorational than functional. It will fail and isn't worth repairing.

[captspillane]

[captspillane]

Here's quote to the portion of my project thread that discusses how I retained the original driveshaft with a NP242 in my Red SX4. It also works to install any of the other Jeep transfer cases available.

I installed a NP242 into my Red SX4 with this rear driveshaft. I've driven it for several years this way and there are no noticeable vibrations or problems. I found out that the XJ slip yoke is directly compatible with the stock eagle universal joints. It pops right off the junkyard shaft and directly onto the original Eagle driveshaft. You can't drive it this way until you disable the original slip joint, however, or the driveshaft will slide right out the back of the transfer case. I initially used two split PVC pipe halves held on by four hose clamps to figure out how much pipe I needed to add. I then found a piece of old steel handrail that had the perfect inner and outer diameter to slide perfectly and snuggly into place.

[jim]

There is a fill hole near the top of the cover.  Force fluid in until it runs back out.

[Eagle1984]

Thanks, so the cover inside the axle goes all the way to the right or left side?. Which one of the 2 pictures shows it in the right place, the first or second one.

[captspillane]

The one with my finger shows it fully extended and engaged. In the picture without my finger you'll see a space between the two sets of splines. That is fully disengaged. You need the coupler to bridge that gap in order for the two pieces of axle to act like one solid piece.

Imagine the outer piece of metal spinning. It is hooked up directly to the CV shaft and thus it must be spinning any time the Eagle's front right tire is spinning. The inner piece and the coupler could be sitting still while you're driving in 2WD. You can't make a spinning object and a stationary object mesh very well without noise and grinding and damage to the spines. That is why the Eagle had to come to a complete stop before being shifted into 4WD. That is also the damage that could occur if the vacuum diaphragm stops putting slight tension on the coupler to keep it in in place. They eventually realized that this disconnect was more trouble than it was worth. It just takes one stone to come up and shear that flimsy little vacuum hose off.

The only change at the transfer case was the vaccuum actuator. The Stop-to-shift version had an input and then an output going to the front axle. The Shift-on-the-fly version had an input and no output. The NP129 transfer case itself is exactly the same.

[Eagle1984]

What is the chance of the front axle disconnect have been destroyed/damaged when it disconnected and destroyed the transfer case? Also if I drive the passengers side up a ramp how would I be able to spin the wheel to get the axle spines even with each other?