87 4runner transmission

i got an 87 4runner and my transmission has been acting up a bit: it grinds whenever i try to go into 4th and whenever i do get it in 4th if i let off the gas it will pop out; also, there is a chattering noise (like there's something loose inside just floating around) in all of the gears except 4th and whenever i downshift it sounds like there is knock coming from the transmission, so i just use my brakes all the time to slowdown now. it seems to me that my tranny is shot and that i just need to get it replaced all completely. do yall have any suggestions of what could remedy this, or any comments?

by the way, its got the 4cyl 22re engine

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You don't have to replace the transmission, just pull it out and replace the synchro rings and splines or whatever parts are worn out. If it leaks, replace the seals on the input or output shafts.