03 Explorer is light flashing and popping into 4th

[Carl Norton]

I have an 03 Explorer with 150,000 miles. The is light has started flashing and it is shifting hard between 3rd and 4th. I keep getting told it's the servo but when I researched it, the of servo works 1-2 and 4-5, while the other servo works 2-3. 3-4 is strictly clutches. Any help on repairs will be appreciated. The fluid was full but did smell a little burnt. Have not dropped the pan yet.

 

[JK080]

Get the codes for the transmission read and post them up, this should give you a good idea on what might be happening. The flashing light lets you know the computer has seen something it doesn't like with the transmission.
Not all code readers can read codes for the transmission especially with the Fords, so go to a shop or somewhere that has a decent scan tool. AutoZone may be able to get the transmission codes.
Burnt smell is not good, this typically means there are burnt clutches or bands inside the transmission and there is no way to fix that in the vehicle.
If you remove the pan you may be able see burnt clutch material that has settled and you will know at that point what you have to do.