That would depend on how much fluid was removed.
Was it a typical fluid and filter replacement or was the transmission removed. If the tranny was not removed. always start with about 4 to 6 quarts.
If the transmission has been removed and the torque converter drained, then about 8 to 10 quarts.
A 1999 Ford F150 with a V6 engine has a transmission fluid capacity of 14 quarts. If performing a pan drop only five quarts of fluid are needed.
if replacing fluid in converter and cooler its 14 quarts
Get 6 that should be plenty
135 quarts in the bed alone.
The 1979 Ford F1 50 pickup truck transmission has a fluid capacity of 12 quarts. The manufacturer recommends that you never overfill the transmission.
Motorcraft MERCON automatic transmission fluid in your 5 speed manual transmission on a 2000 F-150
Mercon 5 transmission fluid
Mercon transmission fluid
The 1996 F150 owners manual shows for the 5 - speed overdrive manual transmission ( Mazda R2 ) - 3.8 U.S. quarts ( 3.6 liters )
type f transmission fluid only
The transmission may shift hard due to it beginning to fail. However, it may also be due to low transmission fluid.
merc V