some pics of a partially disassembled 717.400. Sould not be too bad removing the rear cover from the gearbox and access both sides to get rid of broken bit of speedo.
This is from a gearbox that was missing some parts to warn, so keep an eye out for thrust washers, needle bearing cages, and tiny springs.
here is a picture of the outside of the back cover. white arrow points to reverse idler gear bolt. Remove this bolt plus exterior bolt pattern, and looks like shift arm, and looks like you will be able to tap off the cover.
inside of gearbox this is where that bolt goes to. supports one side of reverse gear shaft-
missing from this pic is shaft ive crudely drawn in that holds shift gate. this is attached to shift gate with a roll pin and will remain stationary, supported in outside cover with a bearing. This missing shaft has an index cut to mate up with the exterior shift gate lever. this is the question mark on reassembly. mine was already undone a bit, so im not sure how you reindex the shift gate lever with the shaft. Ill be back in a few hours and take close up pics of those two items for clarificaiton
inside of rear cover, looks like you will have to remove this inner cage and the roller bearing to access inside of speedo cable hole. I had a lot of loose parts shown outside of case lying around, so watch for thrust washers and bearings and make sure to mark their orientation and take pictures
