A 1991 Ford Probe with a manual transmission doesn't have a dipstick to check the transmission oil level like an automatic transmission does. Manual transmissions typically have the gear oil level checked by a mechanic during a service. There's no readily accessible way to check the level yourself. The level is determined by how much oil was originally put in during a fill (or replacement) and any subsequent leaks.
If you suspect a problem with your transmission (noisy operation, difficulty shifting, etc.), you should take it to a mechanic for diagnosis and repair. Trying to check the level yourself on a manual transmission could result in damage or leaks.
