88 K2500 front axle trouble

[V8trucks]

Hello folks,
My name is Dave, and I recently picked up an 88 K2500. I own a 82 K20 so the IFS is a learning experience. I bought the 88 and was under the impression that the 4WD system was all in working order, untill I tried to move it off some wet grass..... I've read up on this forum about the front actuator, so I bought one and replaced it. Both the old one(which is fairly new anyway) and the brand new one work on the bench with a 12v power supply, and when hooked up to the harness on the truck. But I still have no front wheel engagement. The front shaft is spinning, but not the wheels. A friend of mine has a 95 and he said the front shaft has a very fine(fragile..?)spline on the differential end and was probably stripped, as this had happened to his truck. Any comments or ideas about this theory?
What else is "breakable" in the front diff ?
I like the style of the 88 up trucks, and it rides better than the 82 buckboard, and there's more sheetmetal left too... so I'd like to keep it around if it's fixable.

Thanks in advance
Dave Correll