P0736
P0736-GEAR RATIO ERROR IN REVERSEWhen Monitored:
Continuously with the ignition on, engine running, with the transmission in gear.
Set Condition:
If the ratio of the Input RPM to the Output RPM does not match the current gear ratio. This DTC can take up to five minutes of problem identification before illuminating the MIL
Possible Causes
- LOW FLUID LEVEL
- CUT LR TOWER SEAL ON MAIN VALVE BODY
- CUT LR CLUTCH PISTON SEALS
- BROKEN OR MISSING LR CLUTCH BLEED ORIFICE (IN LR CLUTCH RETAINER)
- CUT LR ACCUMULATOR PISTON SEAL IN MAIN VALVE BODY
- CRACKED LR ACCUMULATOR PISTON IN MAIN VALVE BODY
- CUT OD/REV PISTON SEALS
- BROKEN OR MISSING OD/REV BLEED ORIFICE (IN OD/REV CLUTCH PISTON)
- BROKEN REVERSE CARRIER HUB WELD
- BROKEN REVERSE SUN GEAR WELD TO THE REACTION CARRIER
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Testing and Inspection
Theory of Operation
The transmission system uses two speed sensors, one to measure input RPM and one to measure output RPM. These inputs are essential for proper transmission operation. Therefore, the integrity of this data is verified through the following checks:
1. Once in a particular gear, if the gear ratio varies from the correct gear ratio, the corresponding in-gear trouble code is set (DTCs P0731-36).
2. An excessive change in input or output speeds indicating signal intermittent may result in the DTCs P0715 and/or P0720 being set.
3. If the common speed sensor ground circuit is lost, both sensor inputs will read the pulses from the input speed sensor when at a stop in neutral. Since the input speed sensor reads 60 teeth from the input clutch hub and the output speed sensor reads 30 teeth from the park gear, the result is an apparent speed ratio of 1:2 and may cause the DTC P1794 to set.
Diagnostic Test
1. DETERMINING IF RELATED DTC'S ARE PRESENT
With the scan tool, check for other transmission DTC's
Are there any Transmission; solenoid, line pressure, speed sensor, and/or loss of prime DTC's present?
Yes >>Refer to appropriate symptom in the Transmission category. Perform the test for P0944-LOSS OF PRIME first if it is present. P0944
Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST - VER 1. Verification Tests
No >>Go To 2
2. CHECK TO SEE IF DTC IS CURRENT
With the scan tool, perform the Reverse Gear Clutch test. Follow the instructions on the scan tool.
Increase the throttle angle, TPS degree, to 30°, for no more than a few seconds.
CAUTION: Do not overheat the transmission.
Note: Make sure to record all EATX DTC EVENT DATA stored in the scan tool for future reference in this test procedure.
Did the clutch test pass, input speed remain at zero?
Yes >>Go To 3
No >>Go To 4
3. CHECK DTC EVENT DATA
The conditions necessary to set this DTC are not currently present.
With the scan tool, check the DTC EVENT DATA to help identify the conditions in which the DTC was set.
Does the DTC EVENT DATA show an input speed reading of zero?
Yes >>Go To 6
No >>Go To 4
4. POSSIBLE INTERNAL TRANSMISSION CAUSES
Remove the Transmission Oil Pan and Valve Body and check the following per the Service Information:
Clutch or metal debris in the pan
LR clutch tower seal on the main valve body or cuts and the LR accumulator piston and seals.
Air check the Reverse and LR Hydraulic Clutch circuits (in the case) for excessive air leakage.
Note: Both Hydraulic Clutch circuits contain a small bleed orifice , a small amount of air leakage is normal.
Were there any problems found?
Yes >>Repair as necessary. If clutch debris is present, remove the transmission and inspect the Reverse and LR clutches, and inspect the Transmission Oil Pump and Main Regulator Valve for damage or sticking in its bore.
Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST - VER 1.
No >>Go To 5
5. CLUTCH TEST FAILURE
Did the clutch test fail in reverse?
Yes >>Inspect the Reverse Sun Gear weld to the Reaction Carrier and the Reverse Carrier hub weld and repair as necessary per the Service Information.
Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST - VER 1.
No >>Test complete.
6. CHECK FOR INTERMITTENT OPERATION
Intermittent gear ratio DTCs can be set by problems in the Input and Output Speed Sensor circuits and/or Speed Sensor Ground circuit.
Remove the Starter Relay
Note: Failure to remove the Starter Relay can cause a Transmission - No Response condition.
Check the Speed Sensor wiring and connectors for good connection, then perform a wiggle test using the Transmission Simulator, Miller tool # 8333.
Were there any problems found?
Yes >>Repair as necessary.
Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST - VER 1.
No >>Test complete.