Ewwestsr

Have impeller shaft come apart (cv joints type), busted transfer case in half. Dropped rear shaft, tied up front one and towed home.
know of an exact same year, motor, and tow package donor, but different impeller shaft type (u-joint type) and front yoke.
Should be straight across swap right?
What of dropping transfer case and putting In longer driveshaft for now and making it 2wd?

dave1123

Welcome to CF!

Nope. The transmission needs a rear housing and longer output shaft which requires disassembling the entire transmission to accomplish. The rear housing contains a support bearing that guides the slip yoke of the driveshaft.

You probably have the NP249 constant 4wd, correct? You have that option or either the NP242 or NP231 t/case. You just have to match the input shaft spline size. There is a good write-up on the swaps, however Photobucket has eliminated the pics. It's jeepforum.com/forum/f13/transfer-case-swap-info-np249-np231-np242-685644/

Ewwestsr

Yep, constant 4wd..
Question is did that case have only the cv type impeller shaft, or can I use the one from the donor that has universal joints considering it connects to front of both t-cases via universal joints?
Not sure of donor case type yet, but am going to grab case and both shafts, and yoke from front axel just to make sure I have everything.

dave1123

The CV joint is only in there to make the power smoother. A front shaft with a double carden joint at the t/case end and a single at the diff will work fine. The main problem is changing the diff yoke. It's not a simple matter of unbolting it and bolting on a u-joint yoke. The tension on the nut determines the preload on the pinion bearings and must be done properly or you'll ruin the bearings. I can explain what's involved if you wish to hear it.

Ewwestsr

Please, tell me what I need to do.
I found what's left of the red tag, it's a 249 case.

Ewwestsr

Ok, what if I pull the entire front axel also?
Then I wont have to worry about the pinion bearing right this minute.
Just have to make sure gear ratios match up.

dave1123

For the average mechanic, that's the best way. Axle ratio should be 3.73 on a tow package.

In order to properly change the yoke, OR a pinion seal for that matter, you have to match the "torque-to-turn" setting that exists already in the pinion. To explain that, it's the amount of turning effort required to turn just the pinion on it's bearings, usually about 18 to 20 inch pounds. In order to do that, you need to remove the carrier assembly from the differential, BUT you can get it close enough by removing the tires and brake calipers and measure it that way. Then the nut takes around 150 to 200 foot pounds to remove and replace. We're talking a long breaker-bar and socket while holding the yoke from turning with a pipe wrench or holding fixture. When you put it back on, you take up the slack until the pinion doesn't move back and forth then tighten the nut in small increments until the torque-to-turn the pinion is about 2 inch pounds more than it was before you started. There is a crush sleeve between the 2 pinion bearings that sets the bearing preload so they run smoothly without overheating. Most of the time there is a problem with a differential, it's the pinion bearings that wear out. Some people mark the nut and pinion shaft with paint marks so it's easy to reassemble, but since you're changing the yoke, the marks won't line up.

Most people don't understand that a differential is the most important and least understood part of any drivetrain. They can take a lot of abuse if set up right.

No, it's not easy to do it right. I had a seal changed while having my transmission rebuilt. They installed it too tight and about 50 miles later it exploded at 65 mph! Yes, they fixed it!

Ewwestsr

I know I'll never go back to that cv type impeller shaft as you cant see when its going to fail unlike a u-joint.
As for the differential, I'll swap them out for now and rebuild the original over time. I just need my daily driver back up and rolling under its own power.