Transmission slipping between 35 MPH and 45 MPH?

It sounds like the input shaft sensor is going out. Can I ask if you have a check engine light on? We should run the codes to see if any are stored.

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

I would also check the transmission fluid level and if you have not changed it, we should service the unit.

https://www.2carpros.com/articles/how-to-service-an-automatic-transmission

Here is how to check the fluid out in the transmission in your car and I have included the input shaft sensor location so you can check it out.

Fluid Types
Automatic Transmission Fluid

Ford Part Name

- Motorcraft MERCON LV ATF

Ford Part Number

- XT-10-QLV

Ford Specification

- MERCON LV

NOTE: Automatic transmissions that require MERCON LV should only use MERCON LV fluid. Use of any fluid other than the recommended fluid may cause transmission damage.

Check out the images (below). Please upload pictures or videos in your response to the problem so we can see what's going on.

Thanks again for the quick reply, I appreciate that. yeah, I did take a look at the transmission fluid it looks great nice and pink it's fresh doesn't smell burnt whatsoever and I also ran a scan and the on the car and this is what I came up with on the scan. I'll see if I'll send it to you and see if you can decipher what you think. also, is there a way to test that TSS on that car?

All of these codes need to be fixed, the top code for the alternator please start a new thread for. The last two we need to fix for the transmission problem. Let's change out the TPS sensor and the transmission range sensor and then clear the codes to see if that fixes it. Here is how the job is done. Check out the images (below). Let us know how it goes.

anything?

I will be running a Svan on it tomorrow and let you know what I find.

sounds good ;)