I am considering do a tranny swap, so I was under the car the other day to get the dimensions of my driveshaft. Well, the rear half of the shaft looks weird. Where the shaft meets the center universal joint, the diameter is 5.1cm, or 2 inches.(this is normal I think). This 2 inch shaft, however, "goes into" a larger (6.4mm or 2.5 inches) tube about half way to the differential. There is a small space all the way around between the two and the larger shaft seems to be connected the the differential flange yoke. All of the pictures and drawings that I have seen do not indicate that this larger shaft (tube) should be there. What is it? Does it mean anything? (ie previous repair/damage/wreck?) Thanks for the insight.