2 piece driveshafts

i had a friend of mine take 4 inches out of my driveshaft which came out of a 86 lebaron.there was that same "harmonic balancer" type of rubber and inner shaft that extended about a foot and a half in from both ends of the driveline. it did not go the whole length of the driveshaft. the only way to put it back to together would have been to weld the inner shaft to the end cap and then somehow slide it back in with the rubber around it. there was no way to do that because the rubber expanded after it was pulled out so, we had to leave the inner shaft and the rubber out and just weld the end cap back on the shaft. i had it spin balanced and new u joints put in it and it works just fine. i guess it was just a harmonic sound deadener that they used.