New grease seals fit pretty snug on the spindle, do you have a new seal that you have not installed in a hub, try fitting that new seal on the spindle first before installing the seal in the hub. It sounds like you have the wrong seal or you just need to push a little harder to get it on the spindle.

1957 Chevrolet 5700 LCF 283 SM420 2 speed rear, 1955 IH 300U T/A, 1978 Corvette 350 auto, 1978 Yamaha DT175, 1999 Harley Davidson Softail Fat Boy