My advice would be:
- Make sure that you don't have any front axles. You can see that where the axle tube ends.
- Open the front diff to make sure it's not chewed up real bad, look for gear cogs damage and metal shards in the oil, replace the oil.
If above is all good:
- Get some junkyard left and right axles with u-joints (and bearings with them to save the hassle of undoing the axle nut); Even if your diff is screwed you can still reuse these and u-joints are more robust than CV's anyway. Keep in mind you'd need these with tone rings for ABS, some XJ's and all ZJ's came with those.
- Get a junkyard front driveshaft, CV-style.
- Bolt it all together and see how it goes. Listen for noises at 60-70 mph, growls/whine etc. That'd tell if your diff is good or not.
If the diff is good, proceed to VC diagnosis. If not, get any junkyard D30 front axle from XJ or ZJ (keep an eye for ABS sensor hole if getting a XJ axle)
with same gearing ratio (3.55 or 3.77, whatever you've got). If getting axle from XJ, better get a low-pinion version, high-pinion is stronger but requires a 2-3'' lift. Also if you get an axle with u-joint in front, you can replace your front driveshaft with a stronger u-joint driveshaft.
- To a tight figure-8 turns on a dry pavement, look for wheel binding/hopping and reluctance to go in turn in idle. If you see that, your VC in your Tcase is dead. Then you have 2 options:
a) Rebuild your tcase, install a new VC, costs about $400, good for another 100-150K
b) Get a junkyard 242 tcase and swap it in, costs about $200 and good for the rest of your ZJ life.