Worm and pinion setup. You cannot turn by hand. And you cannot test the motor seperate of the aluminum housing on these. The worm gear is part of the motor armature. It is supported by the motor end bell on the brush end, and supported by the aluminum housing on the other end.
Theres also a small steel ball and spring at the end of the worm gear with a set screw. These parts are located inside the aluminum gear housing, and are there to prevent the worm gear from pulling the motor armature forward in the motor housing and causing it to bind up. These are very small parts dont lose them. I believe later versions only have the adjustment/set screw with a nylon tip on them, but dont quote me on that.
If your going to take this thing apart, best bet is inside the house in a clean area where the pieces wont be disturbed or get lost. Get a nice cardboard box for it all and ziplock bags for the small parts, and take a lot of pix. Theres also really thin shim washers for the pinion, and motor. Dont lose any of this stuff. Snap pix of all the wiring before you unsolder it. Theres 2 contacts on the top of the gear case assembly soldered into a plastic piece. This is for the park feature.
If you look online theres a way to bench test this thing. It's not just add power and ground. Theres also multiple jumper wires that have to be set up into correct config to see low, med, and high, as well as park. The multiple jumper wires are in effect taking place of the dash switch.
When I restored the prestolite Vspeed for my 67 the only thing I was able to test in this way was low, high, and park. Variable speed could not be tested because the jumper wires are not a variable resistor.
When I reassembled the motor and installed it in the gear housing I installed the ball, spring, and set screw, as well as the plastic pinion gear, and ran the motor off 12V while adjusting the set screw. If you set it too tight the motor will bind, set it too loose the motor armature will pull forward. See pix below of the V speed I restored, and you will see why i mentioned indoors, on a clean table, and the cardboard box and ziplock bags for parts so they dont get lost. This is not something you want to take apart on a truck tailgate or a picnic table
Hope this helps
Matt
View attachment 1715534099
View attachment 1715534100
View attachment 1715534101
View attachment 1715534102
View attachment 1715534103
View attachment 1715534104