Glenn - Your driveshaft appears to be the partial torque tube/open driveshaft unit associated with a 3600 (3/4 ton) truck, not for a 3100 (1/2 ton) which would have had the full torque tube driveline.

I think we need more information on what you have before folks can offer more info on what may be leaking.

~ Dan
1951 Chevy 3 window 3100
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"My Grandpa Carl's Truck and How it Became Mine"
1966 Chevelle (Wife's Hot Rod) | 2013 Chevy Silverado (Current daily driver)
US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)