In November of 2018 the starter jammed in the ring gear of my low hour 52 8N.
Upon freeing, I inspected and decided that the starter drive needed replacement. Further inspection revealed that the starter brushes also needed replacement although the commutator and commutator end bushing were both fine. Though I had NOS Ford brushes and a bushing on hand, I decided to replace the starter because I had no way to properly crimp the brush cables to the field, ground, and stud connections and could no longer find anyone locally who I would trust to rebuild my OEM (1,100 hour) starter. The plan was to eventually overhaul this starter at my leisure.
Against my better judgement I ordered a new aftermarket starter with starter drive from my local CNH/Kubota dealer because I could have it in a single day and the cost was not a great deal more than the cost of a good starter drive.
My replacement starter drive came from A & I, complete with a new design starter drive delivered locally for a bit less than $120. It was made in either India or China (can't remember). After installion, the engine cranked faster than it did with OEM starter with badly worn brushes. So far, so good.
Recently, I noticed that cranking speed was slowing even though battery, cables and all else were as good as possible. Yesterday, solenoid click but no crank. Shorting out solenoid with jumper, no difference.
Removing brush inspection band revealed brushes axially out of alignment with commutator by about 1/8", lots of carbon dust on commutator and multiple dead spots. Rotating starter slightly with finger allowed starter to crank engine, albeit slowly and with excessive brush sparking. Mind you this has been less than two years on an infrequently used 8N.
As an aside, the brushes were designed for 12V applications (I already knew this due to inspection of another aftermarket "6V" starter about 12 years ago.) as brush cables were about 1/2 the physical size of the cables on the OEM brushes (stamped Ford) in my OEM starter.
Aftermarket starter is junk and will be continual source of problems, even though working again temporarily and poorly.
Still haven't rebuilt OEM starter, hoping that I would not need to do so. Should have, and now will.
I was spoiled because a nearby friend of mine who had rebuilt starters and generators for over 60 years would professionally rebuild any and all for $35 (unless needing armature or field coil(s), until passing a few years ago. Considering this, I stopped rebuilding such myself about 25-30 years ago.
Wish I knew a good shop that would properly rebuild a 6V starter for less than $250.