Transmission started acting up on me today. It was driving fine until I hill on the hwy. Doin about 65 with cruise on and when I hit the hill the truck wouldn't shift down and speed dropped to about 55 by the time I made it to the top. Turned cruise off when I made it to the next hill, and had the same problem. Pulled off the road and shut it off for a second and when I got on it to get back on the rpms would hit about 5500 and wouldn't shift unless I got off the gas. The od light is flashing and getting a p0503 code. I tried replacing the rear abs/speed sensor but didn't fix the problem. Anyone have any ideas?

 

yes ford has a technical service bulletin on this. if your truck is 4wd you need to try to do remove your speed sensor on your transfer case and inspect the pink gear on the end of it AND if you can look inside the speed sensor hole and see the gear inside the transfer case it probably is all worn out what you need to do is replace both the speedometer gears and maybe the speed sensor on the extension housing of your transfer case.. you are going to need tools to take the speed sensor and extension housing off except (atleast on mine) there is a stupid wire going thru it that you cant unplug so you end up setting it off to the side and the housing kinda hangs there... to take the gear out its very easy... also you are going to need new gears... they're less than 20 bucks from ford... and you might need a new speed sensor... also you are going to need some rtv silicone and some transfer case fluid. i always use chevron MD3 for my t-case. PM me if you have any questions

 

Pulled the sensor and the gear on it looked good. Hard to tell but the gear inside felt fine too. Replaced the sensor just incase and cleared the codes but problem is still here.

 

im willing to bet its more than likely the gear inside... usually the pink gear on the end of the sensor is good but the gear inside is always the one that goes out... heres the technical service bulletin:

This TSB article is being republished in its entirety to correct the parts listed.
ISSUE:

The Malfunction Indicator Lamp (MIL) may illuminate and Diagnostic Trouble Code (DTC) P0503 may be stored in memory. There may also be transmission shift concerns and/or erratic speedometer operation. This may be caused by the speedometer drive gear being loose on the transfer case output shaft.
ACTION:

Replace the speedometer drive gear. The new gear has a tighter fit and should reduce the possibility of erratic signals. Refer to the following Service Procedure for details.
SERVICE PROCEDURE

1. Perform normal diagnostics as outlined in the 1997 or 1998 Powertrain Control/Emissions Diagnosis (PC/ED) On-Board Diagnostics II (OBDII) Service Manual. Service as required.
2. If no concerns were found or the concern is still present, replace the speedometer drive gear.
3. Remove the four (4) rear driveshaft flange bolts and remove the rear driveshaft.
   NOTE:TO MAINTAIN INITIAL DRIVESHAFT BALANCE, MARK THE REAR DRIVESHAFT YOKE AND AXLE FLANGE SO THEY CAN BE REASSEMBLED IN THEIR ORIGINAL POSITIONS.
4. Remove the six (6) extension housing bolts and remove the rear extension housing.
5. Remove the speedometer gear spacer then push the speedometer drive gear toward the transfer case and remove the steel ball. The speedometer drive gear can now be removed from the output shaft.
6. To install the revised Speedometer Drive Gear (F7TZ-17285-AA), reverse the removal procedure.
   NOTE:THE NEW SPEEDOMETER DRIVE GEAR WILL HAVE A SLIGHT INTERFERENCE FIT, HOWEVER IT WILL GO ON TO THE OUTPUT SHAFT BY HAND. DO NOT HEAT THE GEAR.
7. Before installing the extension housing, apply a small bead of sealant to the transfer case cover and extension housing mating surfaces. Use Ford Ultra Silicone Sealant (F7TZ-19554-AA or equivalent).
8. Top off transfer case with MERCON® (XT-2-QDX).

PART NUMBER PART NAME F7TZ-19554-AA Ultra Silicone Sealant F7TZ-17285-AA Speedometer Drive Gear XT-2-QDX MERCON®

 

If gears look good check for intermittant connection/plug/wire corrosion.

 

i agree check for poor connection on the vss circuit... poor terminal pin tension can cause this also... but im convinced its the gear. i had this EXACT same concern with my truck about a year ago... took 20 min to replace the gear (which was all worn out in the center) and its been flawless ever since

 

I ordered the gear on the inside and it should be here tomoro. Job pretty straight foward or do you have any tips on replacing it?

 

yeah dude if your workin on the ground take the drive line out after you block the wheels and set the e brake... if youre on a lift its pretty straight forward you just take the driveline out, drain the t-case, take out the vss, take the extension housing bolts out i believe they are a torx head maybe a t45 or so...they might not even be a torx head. the extension housing should have a wire going thru it... when i did this job to my truck i just left the wire there and just kinda tied up the extension housing out of the way... next just start takin stuff off the output shaft paying close attention to the order it comes off... you will remove the spacer and then push the gear forward as in toward the front of the truck there is a little ball bearing in there that will come out dont lose it and remember how it goes in there... take the gear off and put the new one on and then the steel ball then the spacer... clean the sealing surface of the t case and the extension housing and put some RTV around it then bolt it all down. if you have any questions when you do it you can txt me 503 508 8467. i prefer txt because i work all day and dont like being on the phone incase my boss comes down.... if you call and i dont answer leave a message and i'll call back for sure

 

and remember to fill the t case back up

 

Welp replaced the gear as well as the one on the sensor and truck still won't shift right. Terminal connections all look good so now I am completely lost on what to do