If it jerks then dies, it could be the lockup torque converter is stuck and whenever you put it in drive it's "direct drive" without the advantage of a torque converter. That only applies if the engine is running well and there are no other symptoms. As always, check for a computer diagnostic code using a code scanner.
you need a new transmission
On a 1999 Mercury Cougar : Overdrive is the normally allowed position ( it won't shift into overdrive until the speed is faster anyway ) If you find that the transmission is frequently shifting between overdrive and drive ( such as hilly roads ) then it is best to use the transaxle ( transmission ) control switch on the side of your gear shifter to shut off the overdrive ( O/D OFF will appear in your gauge cluster )
Press CTRL+SHIFT+E
The cable/linkage between the shift lever and transmission is likely broken or disconnected
You press the clutch, and shift gears. There are great instructional videos on youtube.
on yours shift knob that's when u shift from Park to drive in the center is a button when u press it once it its telling you that the over drive is either On or Off so all you have to do is press it again to get it in Overdrive or not in Over Drive
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Check the shift unlock solenoid. The solenoid is known to go bad and cause this issue in a tracer.
Because to press a button to shift a button is like pressing shift to press hard.
1994 mark viii wont shift into 3rd
press shift
The most common problem for the 1995 Cougar xr7 Transmissions is the shift selenoids and the TCM Transmission control modules needing to be reprogramed common fixes for the shift control module would be a transmission overhaul or replacement do to the fact of the shift control module is located inside of the transmission and as well another cost effective fix is to get the transmission control module reprogrammed.