A 1996 Chevy S-10 with a 4.3 liter engine and a
manual transmission does
not have a transmission fluid fill line. Manual transmissions use gear oil, and it's added through a fill plug on the transmission case itself. There's no dipstick or fill line like an automatic transmission.
To add gear oil, you'll need to consult your owner's manual for the specific location of the fill plug and the type and amount of gear oil required. You'll likely need a wrench to remove and replace the plug.
