I installed fun projects pinion set up. With the sealed bearing, will this stop any oil from rear main getting into rear axle?
It will certainly help.
One key to reducing leakage from the engine rear main into the driveshaft is to pack the U-joint housing ball full (FULL) of grease via the large grease cup. The grease will act like a dam, significantly reducing migration of engine oil down the driveshaft tube.
While you're under there, give the small grease cup (for the driveshaft front bearing) a few turns / pumps.
Thanks Mark. The rear axle was not over full when I tore it down so it probably isnt an issue. I think the clunking noise I was hearing may have been the fact there was no pin in U joint. The driveshaft bushing was warn about 1/8 inch in the face. Bad shape ! I will pack ball with red grease about 80% .
When you get done, install that pin in the u-joint. Will keep the U-joint from moving back and forth on the drive shaft and in and out of the tail shaft any more then it has to.