My trans input shaft won't turn. I took off the rear cover and when I removed the the double reversing gear (Porsche manual label) it turns freely. Do I need to go deeper into trans? What could possibly cause this?

Make sure that it is not in 2 gears at once. Pull the shifter console if it's a side shifter and make sure that the notches in the 3 shift rods are all lined up in the middle. If you have a tailshifter you can pull the fork and do the same thing.

I don't know if I count as a transmission guy, but I'll try and help I'm assuming you took off the gear that has two sets of teeth on it but is on a separate shaft than the rest of the gears, and comes off when you take off the tail cover. This gear could only affect things if reverse is somehow engaged at least a little bit. Check the first/reverse shift fork, if the bolt is missing or loose it could cause the problem. What is the history of the trans? Did it work and suddenly stop, or are you reassembling after a rebuild and finding a problem? The transmission will lock up if any two gears are engaged at once, and that would be my first guess. Investigate the shifter, and shift rods. Let us know what you find.

Gotta be two gears at once sooo since you took off the rear cover its first/rev and another gear.

Geoff

Ditto on 2 gears selected at once. Obviously 1st/rev and something else.