How much tranny fluid do you need to put into the transmission of a 1991 Automatic 4Runner?

Check the following:
1 Transmission control rod
2. Manual valve
3. Parking lock pawl.
4. CV Joints.
5. Transmission fluid level.
6. Any dent on oil pan.

is your pump pressure ok filter clean this will all afect how it works

Well if its automatic then you need to add it from the Transmission fluid dipstick.

Hi!
Transmission fluid is added to the tranny thru the dipstick tube, you will need a small funnel. Do not overfill.
Don't forget to rate this post!!

completely drain/flush out tranny,change filter and refill with new ATF,then see.....

Most likely your clutch is out and need to be replaced, If it is a 5 speed manual transmission.
If its an automatic transmission you may need fluid or rebuild.

Drain al the fluid out and go to the dealer or call to find out what suitable substitute can be used usually dextron/mercron transmission fluid but call to confirm. You must now add fluid and run the car in reverse,drive for about ten minutes, drain the fluid and repeat this procedure one more time, you must purge all the fluid out to ensure you have no more incorrect fluid left in trans.

Try having the transmission serviced, get some good fresh fluid in there and have the filter changed. Hope it helps.

Change your transmission fluid and filter

Have you checked the tranny fluid?