What would cause the swing pinion shaft to snap on a Komatsu PC200-7?

[Ryxilo Trader]

I had the swing pinion shaft snap on my Komatsu PC200-7 and I'm trying to figure out what could have caused it. I replaced the oil seal and had to change the bearings because they were completely seized onto the shaft and would not press out easily.

 

[Vintage Irons]

Hey @Ryxilo Trader, if the bearings were seized that badly, there’s a good chance the shaft was running dry or out of alignment for a while before it finally snapped. Once the bearings start binding up, the swing motor puts a ton of extra stress on that pinion shaft, especially if the machine was still working under load.