I am guessing that this is a manual shift .
It has no actual stick .
You must take the speedo cable housing loose at the trans , 10mm bolt and pull it up , the fluid level check is on the end of that assy.
very easy to do .
The transmission dipstick for the 1991 Chevrolet Caprice is located on the side of the transmission. It will be behind a valve cover.
there is not a dipstick on a manual transmission
If it is an Automatic just open the hood and look down at where the transmission bolts to the engine. There you will see the dipstick.
Behind the engine, on the passenger side, just in front of the firewall.
If it is a manual transmission their is not one.
There 's none.
The automatic transmission fluid dipstick is in the engine compartment , near the firewall , just to the passenger side of the engine . The manual transmission fluid level is checked under the vehicle at the transmission fill plug on a 1991 Ford F-250
There is no "cap' you simply go to the autoparts store and purchase a funnel designed for putting transmission fluid into the Dipstick Hole. It's generally about 16 inchs long.
Usually thru the dipstick hole!
Assuming this is an automatic transmission, you can add ATF through the transmission dipstick tube. The dipstick itself will tell you what type of fluid to add.
Transmission fluid is always put in through the Tranny dipstick tube.
Located Left side of Engine compartment look down left hand side of cooling fan near Frame Guru Gonsalves