Speedo and trans issue

Oh crap.
It sounds like you might not have lined the speedo gear up right and it tore up the gear causing it to leak past the seals around the speedo gear shaft.

Also, there is a direction the cable has to be installed or it will unwind inside the housing and seize up.

Hope I'm wrong on both counts.

Fluid IS in the extension housing (normal)
Among other things, the driveshaft yoke bushing (Extension housing bushing) and output shaft support bearing gets lubed with fluid.