Allison 1000 & 2000 Gen 5 Fault Code:P0729 Incorrect 6th Gear Ratio

CIRCUIT DESCRIPTION:
The TCM uses input from the turbine speed and the output speed sensors to determine the current commanded steady state gear ratio. The TCM then compares the known gear ratio to the calculated gear ratio for the current range. DTC P0729 sets during steady state condition when the calculated sixth gear ratio differs from the known sixth gear ratio for a calibrated time.

ACTION TAKEN WHEN THE DTC SETS:
When DTC P0729 is active, the following conditions occur:
1. A shift to 5th range is made when the failure occurs.
2. While diagnostic response is active, if shift selector is moved to N (Neutral), transmission shifts to neutral; if the shift selector is moved to R (Reverse), transmission shifts to neutral. If the shift selector is moved to D (Drive) range and transmission is compromised by overspeeding or direction change, transmission shifts to neutral.
3. DTC P0729 is stored in the TCM history.
4. The CHECK TRANS light illuminates (non-OBD II strategy).
5. The TCM forces Variable Modulated Main off.
6. TCM freezes shift adapts (DNA).
7. TCM inhibits TCC engagement.

CONDITIONS FOR CLEARING THE DTC:
Use the diagnostic tool to clear the DTC from the TCM history. The TCM automatically clears the DTC from the TCM history if the vehicle completes 40 warm-up cycles without the DTC recurring.

DIAGNOSTIC AIDS:
Inspect the wiring for poor electrical connections at the TCM. Look for the following conditions:
1. A bent terminal.
2. A backed-out terminal.
3. A damaged terminal.
4. Poor terminal tension.
5. A chafed wire.
6. A broken wire inside the insulation.

When diagnosing for an intermittent short or open, massage the wiring harness while watching the test equipment or diagnostic tool for a change.

Output or turbine tone wheel damage may cause erratic speed sensor input allowing this DTC to set.

Use the diagnostic tool to record a snapshot of the occurrence, monitor the engine, turbine and output speed signal on the strip chart. Look for erratic or noisy signals, which may indicate an intermittent concern at one of the speed sensor circuits.

Drive the vehicle in 4th range where signals are the same to better determine if signals have a problem.

You may have to clear the DTC and drive the vehicle in order to experience a fault. Use the data obtained from failure records to determine transmission range and/or certain vehicle operating variables such as temperature, run time etc. This data can be useful in reproducing failures mode where DTC was set.

Incorrect ratio DTCs typically indicate mechanical problems with specific clutches for range indicated.

An incorrect ratio DTC may indicate a mechanically failed trim solenoid. Check the DTC information for the specific solenoid.

Incorrect TCM calibration causes this DTC to set. Verify the Calibration Identification Number (CIN) is compatible with the model of transmission installed in vehicle.