sssalah

This is a newly rebuilt t56, with all new timken bearings, new synchros, blocker rings, 1-4 billet keys, 1-4 brass pads...
Clutch is an LS7 with around 1k miles with tick master and new gm slave.
Last night drove it and downshifted from 4th to 3rd at about 50 mph, and dumped the clutch at 3-4k rpm, heard a bang and abs light came on.
What could cause the input shat to split in this way, it is a clean 2 step cut as can be seen from the photos.

85MikeTPI

iTrader: (9)

Looks like it was either shortened or repaired, but definitely welded and broke at the seam/repair joint.

TDP

iTrader: (23)

Yup, its was improperly repaired. I've seen a similar failure where almost the exact same thing happened. It was probably done by the same place that did the shaft in your T56.

Nmbr1GMfan

iTrader: (1)

TDP, why would someone fix one when you can get new for like $200?

TDP

iTrader: (23)

I get them fixed all the time for half the price of a new one. If it's done correctly, then its not an issue at all. The guy that splices shafts for me has rigorously tested the repair. The way that he does it, it comes out stronger than stock. I haven't had one single failure and have probably had 50-60 splices done in the last few years.
The problem is that there are VERY FEW places that will even attempt this. Out of those places, very few of them actually do it right.

thesource

iTrader: (60)

Definately a chop and weld job gone wrong. This is why I have never been a fan of this type of modification.

sssalah

If I knew that it was repaired than I would've changed it during the rebuild. A new one should be in within 2 days, just wanted to make sure that this will not happen again.
Thanks guys for clarification