Today I installed the SYE with the NP231 still IN
just to see how it would go. I did it over the course of about 5 1/2 hours which includes driving to the shop to press bearings out and drive back, and of course time to clean hands, take photos, resume work, etc. I'm not claiming I'm anything special, but it seemed to me it went very smoothly. I rebuilt this unit a year ago on the bench, so feel I am able to make some comparisons. It was easier dealing with pesky snaprings on the bench. That being said, it was still able to be accomplished. The photos I will be posting are from the orientation of laying on your right side down, with your head to the rear of the Jeep, from the driver's side of the Jeep. This way, if you do an install, you will see it from the correct aspect.
First off, the disclaimers--this is how I
did it, it may not go this way for you. Make sure you take any and all appropriate safety measures like blocking your wheels, blah blah blah. I left the Jeep on the ground, wheels on. I also tried to show the socket size in any photos I took while wrenching so you can see what size to use, tried to use appropriate nomenclature, and to reference correct torque values.
Shift your Transfer case into 4LO, then prop up the transfer case tailshaft with a jackstand, remove the transmission mount and torque arm mount from the skid plate. Then remove the skid plate. Using a floor jack place another jack stand under the transmission case and then remove the stand under the tailshaft. Drain out the ATF into an appropriate receptacle. 30mm socket, wrench is on the drainplug. Fill plug is barely visible behind the wrench, below the red tag, better seen in a later photo.
While the ATF is draining, remove the front and rear driveshafts. 8mm socket or wrench to remove the 4 bolts on each end of both driveshafts. Wrap tape around the U joints once removed so the caps don't fall off. I removed the front shaft, then with the rear shaft still in to give resistance, removed the 1 1/8 nut off the flange of the front output shaft of the transfer case as shown in the picture below. It was tight, use a breaker bar if you don't have an impact wrench. I have the impact wrench, I just don't have a big enough air compressor to run it.......
Edit--but now, I sure have solved that air compressor issue.....
Now remove the rear drive shaft, expecting it to spill out some ATF onto you from the slip yoke and extension housing. Next step is to remove the speedometer gear, remove the bolt 1/2" head, and work the speedo assembly out. The unit is "clocked" meaning it is indexed to go in based on the tooth count of the speedometer gear. More teeth, larger diameter gear which means the unit would need to be rotated in the bore to accommodate this if you change your driven gear. The tooth numbers are cast into the black plastic housing. Otherwise if you didn't change the gear, it goes back in same orientation you removed it.
Remove the 3 15mm head bolts holding the rear case extension housing as shown, then remove housing by tapping on tabs with brass drift/hammer.
Next, remove the snapring behind the rear output bearing on the rear housing.
Then remove the 5 10mm head bolts holding the rear output housing to the rear case. I used a chisel as a wedge under the tabs to separate the RTV gasket next. NB
The chisel is not being used to gouge into the joint, the tapered sides of the chisel is being used as a wedge
under the tab to separate the joint.