Truck jumps out of gear?!

[6x6 Dinosaur]

Yesterday I took my truck out for the very first time on the public roads( and thank God they were back roads) to get fuel but I found out that the truck would pop out of gear on downgrades and I have yet to really learn any downshifting but I either put it back into the gear it was in without the clutch or put it in to fourth with double clutching but I noticed it would do it in any gear but mostly 3rd and the shifter has a tiny amount of play in it that I think is enough to be causing this but I need to figure out what It could be.

[dr deuce]

Which gear does it pop out of, 4th or 5th?

[6x6 Dinosaur]

It was doing it to me in third but I think it did it to me in second once as well but I don't really remember that but I know it was third gear.

[dr deuce]

You have some serious problems in the tranny (Like you didn't know this already...). It could be the cover with a problem with the rails, but I suspect a bad bearing or something like that inside allowing something to get out of alignment

[6x6 Dinosaur]

Great! Well I'm out of money at this point to do anything and I'm supposed to put it in a community 4th of July parade and I have to take it tomorrow to get "dressed up" for said parade so I will take more notes on it and see what it does since it can't be fixed this close to the fourth.