P0736-GEAR RATIO ERROR IN REVERSE

For a complete wiring diagram Refer to Section 8W

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.


  • 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


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 45RFE/545RFE Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)



Diagnostic Test

1.CHECK FOR RELATED DTCS



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.


No
  • Go To 2

2.CHECK IF DTC IS CURRENT



CAUTION: Do not overheat the transmission.


NOTE: Make sure to record all 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




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

  • 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


No
  • Go To 5

5.CLUTCH TEST FAILURE


Did the clutch test fail in reverse?

Yes
  • Go To 6


No

6.CHECK FOR BROKEN REVERSE SUN GEAR WELD






Is the reaction carrier turning faster than the drive shell?

Yes
  • Go To 7


No

7.CHECK REVERSE CARRIER HUB



Were there any problems found?

Yes


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. Refer to the Service Information for proper repair procedures.
  • Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)

8.CHECK FOR INTERMITTENT OPERATION



CAUTION: Removal of the Starter Relay will prevent the vehicle from being started in gear.


WARNING: The Starter Relay must be removed from the PDC. Failure to do so can result in personal injury or death.


NOTE: Failure to remove the Starter Relay can cause a Transmission - No Response condition.




Were there any problems found?

Yes


No
  • Test complete.