Does anyone know the size of the ball bearing that is used as a key for the speedo gear on the transfer case shaft for a 1990 f250?

 

Not exactly sure but I would think the ball might be the same as a steering gear control valve uses
3/16 maybe
I have a bunch of small ones I save for the grandkids wrist rockets
I think 1/4 is too big
If you measure the hole diameter in the main shaft, the steelie will be just a bit bigger
I will try to find out exactly for you (if it is in an old manual)