The first vintage engine I ever rebuilt (’53 Super Fastwin) was like this. Some previous owner had packed the gearcase with bearing grease, then ran it for years, turning it into sludge. Molasses is a good way to describe it.
Happily, my company had a de-greasing machine; several ‘rides’ through the machine by the disassembled components made the gears and gearcase usable.
