do you have an automatic in that 230?
you say a 92?
the only 5 speed automatic I recall, was a 722.5, way back in the early 90's, my chart shows that was in the 300 series in 90-93, behind a 3.0.
of course my chart can be wrong.
did not see many 722.5's they did break a weld and would loose 5th gear, or neutral out in 5th. That was a common problem for that trans.
If all the other gears are ok, it is unlikley a fluid change will fix anything.
can you id the trans, usually just above the pan rail, on a flat surface there is a set of numbers, see if you can read a 722. in the set of numbers and then the next 3 numbers after it.

If you have a manual 5 speed, then probably you have gear damage & syncro damage if it is popping out of gear.

email me if I can help further