2000 7.3 automatic suddenly went out of gear going about 30 mph wont go back into any gear, linkage checks fine, no slippage before problem, fluid seems normal good level not burnt no metal, out of ideas!

 

You can pull the pan and check the valve body bolts to see if loose. But it just mitt be time for a rebuild.

 

Input/Output Shaft?

 

There are several things that could have broke to cause this. The only way to know which one broke is to take the trans out and tear it down.

If it is a 4x4 the problem might be in the transfer case. If it is a 4x4 will the truck roll more than a foot or two when in park?

 

its 2wd , being an old c6 guy i'm not very familiar with electronic controls in transmissions but could there be an electrical issue that causes these symptoms?

 

No, there is no electrical failure that can cause these symptoms. The only way to get these symptoms is when something mechanical breaks.

 

ok , thanks for info, i'll pull the pan this weekend and start there

 

You might see metal chunks in the pan, or you might not. Regardless of what you find in the pan the trans needs to come out and get torn down. You can't see any of what may have caused this problem by looking in the pan.