It could posibly be a bad transmission mount or a universal joint on the drive shaft or even maybe loose torque converter bolts
Sway bar bushings
Motorcraft MERCON automatic transmission fluid is used in a 2001 Ford Ranger 5 speed manual transmission ( yes - ATF )
According to the 2001 Ford Ranger Owner Guide : Motorcraft MERCON automatic transmission fluid is used in the 5 speed manual transmission
Motorcraft MERCON automatic transmission fluid is used in the power steering in a 2001 Ford Ranger
According to the 2001 Ford Ranger Owner Guide : Motorcraft MERCON-V automatic transmission fluid ( see if the type used is engraved in the dipstick to confirm )
Motorcraft MERCON automatic transmission fluid for the 5 speed manual - YES ATF ! Motorcraft MERCON V - ATF for all the automatic transmissions in a 2001 Ford Ranger
In a 2001 Ford Ranger the automatic transmission fluid requirements will be indicated on the automatic transmission fluid dipstick or the handle ( Motorcraft MERCON - V according to the Owner Guide )
I'm not a mechanic / technician but the automatic transmissions on a 2001 Ford Ranger would be electronically controlled , so there wouldn't be a modulator valve
A bad transmission.
Sounds like the transmission
I believe the neutral safety switch is mounted on the side of your transmission
According to the 2001 Ford Ranger Owner Guide : For the 4.0 liter V6 engine : The engine cooling system capacity is : ( with manual transmission / 13.0 liters / 13.7 U.S. quarts ) ( with automatic transmission / 12.5 liters / 13.2 U.S. qyarts )