I recently rebuilt the transmission in my 04 F150. I have installed a low stall torque converter. I also installed a shift correction kit. When I started it up and took off I got a code P0731 saying that the first gear ratio was incorrect. On take off it is a little slow until I get to about 2000 RPM and you get a sudden surge of power. It shifts through the gears just fine and acts normal in all other gears. Could this be one of the seals in the transmission not completely sealed or the spacer in the transmission pump. When I did the rebuild I had to replace the transmission pump due to damage caused by a warped flex plate and the spacer was completely destroyed. So I am unsure of which spacer is required. I did pressure test during installation and all seemed to be fine. Any help would be greatly appreciated.

 

@Michael Berry


There seems to be an oxymoron here - you sound like you know what you are doing. Especially if you rebuilt the transmission yourself, and for that I would give 'hats off' to you, as you just damn well probably know more about it than I do.


But on the other hand, the problem you describe seems to be exactly what would happen by changing the 'stall' speed of the T/C.


The ECU (as part of the 'comprehensive components monitor' routine(s) monitors actual gear position and compares that rationally to the torque converter slip ratio as follows:

Torque converter slip ratio = A x C/B, where:

A: Output shaft revolution signal from revolution sensor
B: Engine speed signal from Engine Control Module (ECM)
C: Gear ratio determined as gear position which TCM supposes

If the actual gear position is higher/lower/different than the position (1st) is supposed by Transmission Control Module (TCM), the slip ratio will be more/less than normal. In case the ratio exceeds the specified value, TCM judges this diagnosis malfunction.


As for your 'burst' of power --- the Torque Converter 'STALL' speed is matched to the torque curve of the power plant. So when yours reaches its peak power curve - it's already been in gear trying to get going for a time.


Although I haven't rebult one myself, it seems this result would be guaranteed. Not sure I have a real intelligent suggestion.

Perhaps some tunes might be able to adjust ECU parameters to match the different T/C

 

[QUOTE=F150Torqued;5523682]@Michael Berry

Not gonna lie. I did the rebuild by a YouTube video. Wasn’t very difficult. Guy that made it did a very good job of tearing down and piecing it back together. Also did quite a bit of research before tearing into it.

I assumed there would be problems with the ECM but I could not find anyone with this problem or any ecm modifications. Changing the tune didn’t seem like it was necessary. I have tore back into the transmission pump. I did notice a Knick in the bonded seal. (Came pre installed on the pump I bought didn’t think to check a new seal.) I am going to rebuild this pump and put it back together.

I’m thinking it was causing enough pressure loss to make the transmission engage improperly. After that I guess I’m gonna have to find someone to re program my control module.

 

@Michel Berry

I think your code (P0731) pretty much says it all with respect to the problem/symptoms you described.

I don't know if it would be of any further help, but if you have a good scanner (specifically one that can read and display non-standard, custom PIDs), I have about 30 to 35 FORD custom OBDII PIDs relating to the Transmission that I could provide. I have scanned, dug up, researched, hacked, and worked out formulas for a dashboard screen on Torque Pro. A recent screen shot is below though I have moved things around and added a couple more recently.

There is a bunch of interesting _stuff_ that Ford provides via OBDII on the tranny - examples such as: Line Pressure Desired (LINEDSD), Transmission Line Pressure (TLP), Pressure control Amps (PCA AMP), Trans Selector Position (TSP), T/C Control Solenoid (TCCS), T/C Control Pressure (TCCPC), T/C Slip (TCS), ~~~~~~ input and output shaft speeds, with actual calculated gear ratio ((I think this is what's causing YOUR problem)), shift solenoids one and two state, milliseconds shift lag and flare with RPM rise/drop between each shift .... and on and on including trans temp and a bunch of different failure flags.....

There is *ALSO* a 'self preservation' FLAG that might explain your symptom. It's designated Torque Control State (TQ_CNTL), at OBDII PID 095E. This PID produces an 'integer' that is coded as follows:

0= No Torque reduction requested
1= Torque Truncation. Cuts fuel to protect when line pressure fails to minimum limit
2= Torque Control Event - cuts fuel and/or spark for traction control.
3= Vehicle Speed Limit - Cuts fuel

The Transmission pressures might not be built up enough at lower RPM (by the lower T/C "Stall" speed), and the ECU might 'truncate' Torque by cutting fuel / or limiting throttle position until a higher RPM is reached. /// I actually thought the lower stall speed T/C was intended for diesel power plants which produce their maximum torque at much lower RPMS. You might ultimately have to go back to the standard T/C to fix this problem. ///



TORQUE PRO Transmission Monitor dashboard