Interesting video on making a chain drive diff unit without welding or using a lathe.
https://www.youtube.com/watch?v=aah2ufNfu9Q
I presume that you meant https://www.youtube.com/watch?v=8Xi04c4ozg8
"without welding or using a lathe"
you sure?
Have you got the right link? This one appears to be for a 2-speed transmission (and he spends most of it using a lathe).
Oops, wrong link. Heres the correct one!!!
https://www.youtube.com/watch?v=8Xi04c4ozg8
[Edited on 9/8/21 by myke pocock]