Overdrive not working properly

I assume this is at highway speeds that it feels like it shifts to neutral? Does it do it all the time at a certain speed or is it random?

I would start with checking the fluid level and condition. Then we need to check for codes.

I suspect this is either a fluid issue or a possible torque converter solenoid issue but I would expect a code to go with that.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Below is the process to check the fluid. Let's start with this and go from there.

Unfortunately you are probably correct that changing the fluid at this point will not correct it but it is a sign as to what is happening. At this point you have a clutch issue caused by a solenoid issue in the valve body.

We should check for codes as I suspect you have some that will point to a specific solenoid.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

What I suspect is the fluid deteriorated and the clutches started slipping. Then that burned the fluid and made it worse. Then eventually the solenoid gave out. There is a chance that it went the other way which is the solenoid failed and you lose the specific gear.

However, that is normally accompanied by a check engine light.

The P1754 is the cause of this. This code is telling you that there is a wiring or solenoid issue. Basically these solenoids are what controls the direction of the fluid which is what engages the clutches for each gear. So when you are reaching this gear the solenoid is not changing the direction of the fluid in the valve body so that 4th gear can engage. So it doesn't engage or it takes a while and then it sets this code.

Below is the info on this.