I've got a non world-class T5 that's basically in good shape except the main shaft is spent. I've got a freshly rebuilt WC T5 with a broken input shaft. Can I use the non WC input shaft? I haven't cracked the WC T5 open yet (because I don't want to go through the work if it's for nothing). My non WC trans had a timkin bearing on the input shaft, and they look the same on the outside of the trans (as I would expect them to).

 

Nope, the main shaft is different. The WC has much better lubrication. My main shaft got chewed up pretty good on my WC. I took it apart and had the tranny shop re-weld and fix the input shaft that goes into the Pilot Bearing. I put a roller Moroso pilot bearing on their and things have been awesome since (3 years ago). Get your WC fixed if possible, or try and find one from a tranny shop.