My son's truck is having a automatic trans issue. It's a 2002 F150 Sport 4.2 v-6 with the 4R70W, Trans code "U" on the door sticker. The truck runs great, 212k miles, unknown history before I bought it 3 years ago. Recently, it has developed a strange problem. When the engine is warm, after driving highway speeds, the transmission drops into neutral when slowing to a stop. The O/D light on the shifter will begin flashing. It shows a trouble code PO755, but not sure if this is related. If you rev the motor, or pull the shifter down a notch, it goes back in to gear and shifts normal. The fluid is good, I had the pan off recently and saw no metal. The column shifter seems a little sloppy, could this be a factor? I've checked the adjustment on the linkages and all are good. The problem is it is intermittent. Hate to get burned for a new trans if I don't need one......any help is appreciated

 

P0755 is you problem.. Shift solenoid B malfunction. have a trans shop replace that solenoid for you.

 

Thanks for the help. Is this something I can (or should) tackle myself? I have a chassis lift and trans lift. (I build muscle cars). I service my own transmissions and have installed shift kits, just never gone farther than the valve body. I have a transmission parts store nearby. Are any special tools required?

 

Was not sure how knowledgeable you were … should be cake for you. valve body drops down with a few bolts.

 

Thanks for the help. Most of the stuff I work on is pre-computer, so I get a little nervous tearing into something like this. Not many of us around anymore that know what a carbuerator is!

 

I have a few Holly re-builds under my belt. Rockauto has the shift solenoids starting @ $16.

 

Problem solved. I replaced all the solenoids and the hard plastic internal wiring loom. I was able to get all the parts locally from a Transtar Transmission Parts store. Total cost including new fluid and filter, about $160. Took about an hour to complete. I would recommend replacing all 4 parts while you have the pan off. Easier to tear into once than keep going back. On a difficulty scale of 1-10, I would give this job a 3. It can be messy, as these do not have a drain plug. There are a couple of Youtube videos that show this being done if you want to see what you are getting into before you start. Thanks for the help!

 

Good job, thanks for the update.

 

Glad that got her fixed.. you could of installed a new dorman pan with a built in drain for next time.. they are rather inexpensive and not messy at all.