first time post. m818 shifting issues

[cederrowe]

So picked up my first big truck. M818
On the drive home the five speed has a lot of grinding issues between 2nd and 3rd. Also we had to tie the high low selector back to stop it from popping out of gear. Used the search engine but not finding were I should start inspecting?
74 m818
8615 miles
5ton
5 speed
Thanks for any help in the right direction.

 

[doghead]

Inspect the oil and it's level.

 

[cederrowe]

Inspect the oil and it's level.

Level was fine. Maybe broken down and thin??

 

[73m819]

Second/third syncro is bad, the transfer synco is also bad, as well as the detent is worn