Ok, I have searched everywhere and cant find the answer to my issue. I have a 2001 Expo 4.6l 4r70w trans. It shifts fine in every gear. However, when in overdrive it constantly wants to down shift. It only does this when the trans has warmed up. When driving at about 50 mph it will all of a sudden start fluctuating from 2000 to 1200 rpm in and out of shift modes. It never slips but just kicks in and out of the two gears like it cant decide what gear it wants to be in. If I turn off the overdrive it will hold a constant 2000 rpm at 50 mph and shift through all the gears fine. Also my 4x4 light is flashing but Im sure that is a sensor issue since all my 4x4 functions work fine. Im hoping an easy fix but would like some guidance before I take it to the dealership Friday and have a scan done. Side note: I took it to auto zone to have it scanned but only came up with an O2 sensor malfunction. That would explain the check engine light that has been on since I bought it. Thank you.

 

What are the exact numerical codes?

 

Autozone CANNOT read transmission codes. Your computer could have 20 transmission codes stored and Autozone won't see a single one of them.

If you want to fix this take it to a good independent shop or a Ford dealer and get the codes read.

Or if you're into changing parts on guesses change the TRS (Transmission Range Sensor,) also known as the MLPS (Manual Lever Position Sensor,) or NSS (Neutral Safety Switch.) there is no guarantee that this will fix it, but it might.

 

OK. A little update. Took the truck into the dealership and had an IDS scan done. seems I had a few things going on. One was a bad coil on #1 cylinder. Plus a trans fluid change has seemed to fix the problem. however I still have a code P1824 which is for a relay in the 4x4. The 4x4 works fine but the light blinks in the dash. anyone with any ideas let me know. it is hopefully the last thing I have to fix.