Best engine oil for 98 1500LC 11,000 miles, Shifts hard

Usually bad "solenoid pack" inside automatic trans. Although, you usually also get a slight hesitation followed by a "clunk" when switching from forward to reverse. Also possibly computer programming error. If it has "adaptive" shifting (i.e. "computer learns your driving pattern and shifts accordingly"), you can have Ford change the programming to a standard shift pattern. (It's a wonderful difference in transmission performance).

Sounds like engine mount or strut support get them checked by the shop u purchased from

The clunk is from an engine mount that is bad. Have them checked.

Why do you rev the engine? Need more info. don-ohio (:^)

When the trans is cold it will shift almost normal as of now. If you keep driving it it will eventually slip when its cold. This is caused by worn out clutch plates
Your trans needs to be overhauled with a clutch rebuild kit

Is there something in your trunk?
Check motor mounts and c/v joints.

could be a vacuum leak. When rpms are up, it has enough vac to operate properly. Check all vacuum hoses and make sure they are all on, and look for splits or cracks in the hoses

I would check the transmission and engine mounts but also it may be time for a transmission fluid change. It has a service interval just like oil. 50000 miles

the error P0113 still comes up even after a new sensor was installed and the transmission shifts very hard. Found a break in one of the wires to the sensor. Soldered it back to gether. Found that the engine has a limit to the rpm when rev-ing in neutral.
Thanks
rkbids