i had that issue on the front joint on the rear shaft of my 40. so i took it to a spicer rep. and he got two new joints, a spicer and another name brand and neither would fit. the cross wouldnt slip in to install the cups. he then got a new spicer youke and the yokes were configured slightly from the old days to current design. he said to just grind just enough off of both insides of the yoke until the joint slipped in. i did just that and no more issues.
