There is a set screw either 3/8 or 1/2 drive ratchet will fit on the middle of the cover and off to the side a bit take it out and fill with 90 weight gear oil untill fluid comes out the same hole then replace the screw

A sticking pilot bearing. 2. Damaged shift linkage Try holding down clutch abnormally long between gears. if you can shift this way, your synchronizers are worn.

sounds like a hydraulic master/slave problem...they might be getting weak

this is an internal transmission problem. have you reset the code to see if it comes back?

hook up a scanner and check for history codes if the check engine light came on it will save that data and let you know what code it read when it came on. that will get you started in the right direction. These transmission problems are usually internal. so the transmission may need to be rebuilt

Code didn't register so that's why I'm stumped as to the cause

This is one of those questions that few (even the best) mechanics will know the answer to. You need to find out how many different flywheels there are for this engine application and look, measure, decide which one is needed. You are the star of your show, that is what I have learned over the years when I was asking others for answers I never got. Use all the sources you can, stop at a Chrysler dealer with coffee and donuts and that may be the best shot at accurate info. I still do that. Sometimes when I need a lot of info I do Pizzas and garlic knots for a half dozen guys. Trust me, they will almost assemble the job for you.

the shifting syncronizers are bad need to get trans rebuilt or replaced.

There is no easy fix to transmission problems. Your going to have to bring it in to get looked at.

Sometimes they are very stubborn. Use a wedge between the tran case and the inner cv housing. Be careful though. Be precise about where you pry against as you do not want to crack the trans case.

Try a battery disconnect for a few minutes and check the fluid level. It is in what is called "limp" mode because there is a problem and the transmission computer has defaulted to this mode to protect the trans from further damage.

you might want to change or flush the trans fluid

Sounds like your rearend is shot. The same thing happened to my mustang when I first bought it. The rearend was making a grinding noise when going slow. Ford found that the gears were worn.

Sounds like a motor mount or transmission mount is broken. If just one is broken it can cause a transmission to shift wrong or very hard.

Yes, stop at a large auto parts chain store and ask them to read the codes for free. AutoZone will.