84 problems

hey i have a 84 s-10 2.8 that i have owned now for 2 years andsin those two years i have a recurring problem that doesn't always happen, the truck will work fine and as you drive along to work it seems to completely lose power and can't even get you up to 10 miles hr then you sit on the side of the road and wait and haha it will work fine and may not return for a month or two but may recur everyday for a month. i have changed the fuel filter and cap rotor combo with no avail, it also seems that when it is working bad and you try and give it more gas it seems to jump out of gear and into neutral, but i'm not really sure.. any sugestions.

im going to assume its an auto. and im going to tell you its probably going to need to be rebuilt. might wanna take it to a trans place and see if they can do anything for you.