Differential change and transmission trouble

Posting for a friend with a 2001 2wd V6 Tundra who had his rear axle replaced about 2 months ago due to the housing rusting through.

Fast forward to this weekend while his daughter was driving on the highway, the truck started acting like the transmission died.

The engine was still running but the truck just wouldn't move.

He pulled the splash shield and the converter is still bolted to the flywheel but he can spin the whole assembly by hand.

It seems either the hub broke out of the flywheel,, or worse, the rear main bearing broke off the crank shaft.

I don't know much about Toyotas but I'm wondering if the read end replacement might have had something to do with this problem? It was replaced by the dealership where he bought the truck new but who knows what could have happened?

I'm thinking maybe a design change somewhere along the line maybe moved the rear end forward enough to put pressure through the trans and into the flywheel.

Crazy thought I know but I've been working on cars a while and never saw something like this happen without some major stress on things.

Any suggestions would be appreciated.

Thanks.

I am not sure about Tundras, but I have seen cracked flexplates break around the crankshaft bolts on other vehicles. Often the flexplate becomes noisy and knocks before breaking. Hopefully, this is not a big deal to fix.

I cannot see the rear end trouble contributing to this. I suspect its just a coincidence.

The driveshaft should be connected into the transmission tail shaft through a splined slip yoke. Any change in geometry would be taken up by movement in the slip joint which is designed to slip when the rear axle moves up and down.

I'd check for any TSB on this problem or mfr recall, but it could be as simple as a stuck valve body component or a shift control computer going into "safe" mode. Any trouble codes stored in the ECM?

No trouble codes or anything. Seems to be bad luck I guess. Flywheel was replaced and so far so good. Thanks for the replies.