I have a 1994 Lincoln Town Car, Signature Series. 4th gear not working, has over 200000 miles on it. All other gears working fine.Do I need another transmission?

it needs transmission work, worn gears

boot wont unlock pergut 307

first thing to check is transmission oil level and quality. If that is fine than your looking at either a valve body problem (valve body is what controls the selection of gears) or possibly a problem with the bands on the planetary gear set, they can be tightened in certain models. However i dont think it is the bands.
Does the overdrive only engage 4th gear? or does it feel like the gear ratios are different between overdrive and normal before the problem happened? some overdrive buttons engage final gear and some do as much as change gear ratios like in a cvt (contantly variable transmission) and some just change the timing in the gear changes to provide more rpm/power.
My best guess is that the valve controlling the overdrive in the valve body has failed and therefor you dont get a response from the transmission (i.e no gear shifting when overdrive is selected)

Check the oil level inside. The automatic transmisions are working oil based. If not enough oil, not enough pressure for moving the hidraulic mechanisms inside. The clutch is also actioned by oil pressure.

what other year than a 1994 will fit on a 1994 lincoln towncar

how can i get the code to the lock on the driver door if im lock out

There are three kinds of brake pads,I prefer the middle ones,
1= cheap but wear fast
2=normal cost,and last about two to three years,
3=expensive,pads are ceramic and squeal coming to a stop

air idle control motor probably sticking remove motor and spray w-d-40 inside then reinstall and tap with a hammer while running

Bring it to a mecanic for a tranny tune up