Single Rail Gear Box won't rotate.

[Kiwi Cortina]

I pulled the import snout off the box to replace the gasket, loosened the tail shaft and when I went to tighten it all back up again the shafts will not rotate. Loosen the bolts off a little the shafts will turn but when in neutral both input and out put shafts turn. 3rd gear seems to be the only gear working the way it should. Any suggestions? Hopefully not a rebuild. It was functioning correctly before I started.

Thanks

[peteleo]

Brent,

Don't quite understand what's going on. You loosened the tail shaft to replace a gasket ?