Tranny pops out of 5th

I have a 1993 Escort LXE with a 5 speed. 165,000 miles.Transmission works great until we are on the highway for about 10 or so minutes and it slips out of 5th gear. Goes back in okay but won't stay long. Is there an adjustment for this I can do myself and what is the posibble cause of problem?

ok i heard that every 65,000 the tranny goes thats jsut what i heard but i had my tranny go and it was starting to slip out of gears so what every it is plan on getting a new tranny sorry bud

well i have a couple more than 65k haha and my tranny is strong...yours however doesn't seem to have the same luck. I'ld look into a local junkyard... just my suggestion. Good Luck!!