I am baffled!

[TNDRIVER]

The splines on the input gear appear to be fine. So, I'm thinking I must have a 12K input gear in my 10K hub. Will a 12K half shot bolt in?
First two pics are the old shaft, last one is the new one. Both of these shafts are too small to fit the input gear.

PLEASE..... when you get this figured out, let us know. You have one of the stranger issues I've seen here. I might add, I "think" the 12k axles also have a different washer with the outside bolt.

 

[maggie8264]

Maybe @Retiredwarhorses can shed some light on this, if anyone aside from everyone already on this thread is going to know or have experience with an oddball HMMWV issue like this I think it'd be him. I would try the washer thing mentioned earlier myself, seems the simplest place to start.

This is what i think happened. Either the hub was replaced with a 12K hub or the input gear was changed to the 12K gear. And The half shaft was not changed to the 12K shaft. Because neither shaft will fit, both are too small.

 

[Mogman]

Maybe @Retiredwarhorses can shed some light on this, if anyone aside from everyone already on this thread is going to know or have experience with an oddball HMMWV issue like this I think it'd be him. I would try the washer thing mentioned earlier myself, seems the simplest place to start.

OP says the new and old shafts turns inside the input gear so not a washer issue.

 

[Mogman]

This is what i think happened. Either the hub was replaced with a 12K hub or the input gear was changed to the 12K gear. And The half shaft was not changed to the 12K shaft. Because neither shaft will fit, both are too small.

It is strange that this did not show up earlier unless you had/have the transfer case in HL otherwise the truck should not have gone anywhere, no matter how tight the bolt was it was not going to keep the shaft from turning in the gear, whoever sold you the truck may have put it in HL so it would appear to drive normally.
Looks like you need to find an A2 shaft to try....

 

[maggie8264]

It is strange that this did not show up earlier unless you had/have the transfer case in HL otherwise the truck should not have gone anywhere, no matter how tight the bolt was it was not going to keep the shaft from turning in the gear, whoever sold you the truck may have put it in HL so it would appear to drive normally.
Looks like you need to find an A2 shaft to try....

It seems like there is more than one 12K shaft, does anyone have a part number for the one that will fit?

 

[Mogman]

RCSK17028-3 and/or 252001421458

 

[Dieselmeister]

It is possible that you have a 12K gear. Many years ago I wanted to increase the strength of my axles, and bought an 12K upgrade kit from SAX, which involved replacing the 10K gears with 12K gears, new bearings, and 12K axles. Both gears fit in the same housing.