P0736
P0736-GEAR RATIO ERROR IN REVERSE
For a complete wiring diagram refer to Diagrams/Electrical. Electrical Diagrams
- When 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
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. 45RFE/545RFE Pre-Diagnostic Troubleshooting Procedure
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. 45RFE/545RFE Transmission Verification Test
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 8
No
- Go To 4
4. POSSIBLE INTERNAL TRANSMISSION CAUSES
Remove the Transmission Oil Pan and Valve Body and check the following:
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. The Reverse hydraulic clutch circuit bleed orifice connects to the OD hydraulic clutch cavity. A small amount of air leakage into the OD hydraulic clutch circuit is considered 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. 45RFE/545RFE Transmission Verification Test
No
- Go To 5
5. CLUTCH TEST FAILURE
Did the clutch test fail in reverse?
Yes
- Go To 6
No
- Test complete.
6. CHECK FOR BROKEN REVERSE SUN GEAR WELD
Working through the windows in the bottom of the case, check for a broken Reverse Sun gear weld to the reaction carrier as follows:
(1) Hold the Transmission Output Shaft by holding the Transmission Manual Lever in the park position.
(2) Rotate the Input Annulus gear and drive shell, (the drum that encloses the two rearmost carriers).
(3) Check to see if the reaction carrier (the frontmost carrier, whose outer shell is splined to the 2C clutch) is rotating faster than the drive shell is being turned.
Is the reaction carrier turning faster than the drive shell?
Yes
- Go To 7
No
- Replace the reaction carrier.
- Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST - VER 1. 45RFE/545RFE Transmission Verification Test
7. CHECK REVERSE CARRIER HUB
Remove the Transmission and inspect the weld on the reverse carrier hub.
Were there any problems found?
Yes
- Repair as necessary.
No
- Disassemble and inspect the input clutch assembly. Check the Reverse clutch reaction plate snap ring. Check the OD and Reverse clutch seals, discs, and bleed orifice (in the OD/Reverse clutch piston). Check the Reverse hub and shaft. Repair as necessary.
- Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST - VER 1. 45RFE/545RFE Transmission Verification Test
8. 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. 45RFE/545RFE Transmission Verification Test
No
- Test complete.