Broken steering shaft

I'm new to the group. I've been a Toyota owner for 40 years. Owned over a dozen Tacoma's and now 3 tundras. I thought the tundras were even more reliable than the Tacomas until yesterday. I was driving home on my dirt road and made a slight left turn at less than 5 miles an hour. My steering shaft broke where it goes into the intermediate shaft on the firewall of the floorboard. Of course I lost all steering and had I been going any faster it would have been bad. Does anybody have any ideas why? The 04 did have rust damage on the frame when I bought it. About a month ago I had welded all day back on the bracket on the rack and pinion nearest the steering shaft. The tack weld on it had broke so I welded back on the original bracket in the exactly the same place. Matching up the broken welds. That's the only time I've touched the steering. I had been driving it without problems ever since. Other than that I've never had any problem with steering in any other Toyota. It's an easy enough fix replacing the steering column but I don't want it to happen again. Anybody have any ideas why?

Here's a photo of the shaft

https://photos.app.goo.gl/LcM6dGocEw3stkUy6

 

Can't say I've ever seen that happen before. I don't even have a clue how it would happen. And we've seen a lot of stuff here.

 

I'm guessing this is why it ended up breaking

 

Some better pics of the actual break might help. Can't tell if it is a shear, if it was a 'twist' break, signs of metal fatigue etc.

 

Yeah, exactly what bracket is he talking about? That’s what’s confusing me.

 

The bracket I welded on was the bracket on the passenger side of the rack and pinion. I don't see how that could affect the shaft on the opposite side. It was a clean break just inside the splined receiver right above where the bolt goes through. I just got done putting in a new to me steering column that didn't find anything else wrong when I was doing it. Everything seems to be working fine but I'm hesitant to drive it till I bring it to an alignment shop and they look at it. There was virtually no pressure on it when it broke. Like I said five miles an hour at a slight left turn.

 

Any accident history on the truck?
Since the steering shaft doesn't usually see much force it could have been cracked for a loooooooong time due to something a previous owner did.

 

It was hit on the back door on the driver side crew door prior to me buying it in 2019. That was 50,000 miles ago. When I looked at the break it was clean with no obvious rust where it like it had been cracked. Now I've replaced the column the steering does seem a little stiffer than on my other Tundras. Not sure why. I could move the wheels freely back and forth with the front end jacked up before I installed it.

 

Did you weld the bracket or the mount? The bracket is available from Toyota - I replaced mine a couple years ago. If your frame is rusty and you repaired the mount, it may not be aligned correctly and the shaft could have been trying to twist against the rack causing a break in the weakest spot.

Since you replaced it - you'll probably see if it breaks in the same spot again.

Good luck, sounds tough to really troubleshoot as it's really uncommon.