There are two drain plugs on the driver side of the vehicle.Fill hole at top and MAKE DAMN SURE you use a tight fitting socket/wrench to remove it. If you've ran it desperately LOW on fluid then you've ran a HIGH risk of burning your synchros. These trannies run on a slight pump fed pressure to positively engage the synchros; reliable technology for the light duty use of the vehicle. If you cannot get your shifter into the respective gates for 1st and Reverse then do exactly what John said... but if that doesn't help... rebuild the unit whole!

A nifty trick to fill that gearbox is going and getting a quart despenser with a shut off valve - remove the 18" clear vinyl hose and get about 48" from a Home Depot/Lowes. Jack the car up at the Driver side Front lift point (behind the front splash-flap) and squeeze AUTOMATIC FLUID INTO IT - these things need ATF since they need pressure rated fluid to push a few synchros... Over fill it. Remove the hose and cap it as quickly as you can. Test drive... make your decision to scrap or rebuild if it doesn't meet your standards.

2cents
Tim
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'92 244 NOW w/ M47 (Hydra, turbo bars, bilstein, urethane bushings)