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Thread: Duramax tranny shifting problem

  1. #1
    ECeptor
    A buddy is having the following symptoms on his 2001 2500HD 4wd Duramax / Allison:
    -Service engine soon light
    -ABS light
    -Parking brake light
    -No speedometer function
    -No reverse
    -When I put it in drive, I think it is in 3rd (whereas when it failed on Sunday, it stayed in low)
    He recently cleaned what he thinks to be the speed sensor (on the output housing of the transfer case) but it did not appear to be dirty at all. He recently replace the neutral position sensor.
    He just bought a code reader and I'll post as soon as he has that info.
    Thoughts, ideas, suggestions?

  2. #2
    N2Lake
    Oh no a Allison with shifting problems. We are all DOOMED
    Just had to say that. Sorry your having troubles with your truck, I am sure a good dealer will be able to fix it.

  3. #3
    UnionJack
    Had the same thing last week, the wire that connects the tranny to the motor got riped out, quick fix at your local Chevy dealer..... warranty

  4. #4
    Jordy
    I've also heard of problems with the shift position sensor on the left hand side of the tranny I believe. It's a black box, that apparently wasn't watertight on the early ones and will give fits and make it go bezerk, much as it sounds like it's doing. I'd check that first, especially with all the rain we've all had lately. Get some water/dirt/road grime up in there and all hell breaks loose.
    If something was really wrong with just the tranny internally, he should just get a service engine light and it would limp in 3rd gear.
    Good luck.
    Jordy <----- has an inside source on Allison info

  5. #5
    BADBLOWN572
    Buy a Ford. :idea:

  6. #6
    djunkie
    Damm finally a tranny problem. About 2 million more cases and aliison may catch up to the ford failure percentage.

  7. #7
    Just Tool'n
    Is it me or does it seem that Fords have way more tranny problems than GM.
    I was in training a new dealer last friday, stop at the local Ford dealership, we park out by the parts dept. The have those black cases that they ship tranny's in, stacked 2 high & 50 ft long just of tranny's.
    Then we walk in the back door of the dealership, & they have a pallet of probably 10-15 diffrentials like 3rd members sitting there, all have been changed out, I know there not out of trucks, as they are all out of smaller vehicles.
    I just dont see that at the chevy dealeryship I was in just 2 days earlier in the week.

  8. #8
    UnionJack
    Did it get fixed?

  9. #9
    ECeptor
    Not fixed yet. Here's an update:
    "Have replaced the Output Speed Sensor and the sensor on the output shaft of the transfer case. 60A ABS fuse tests good.
    Symptoms:
    - ABS light on when you start it.
    - No speedometer
    - Won't shift out of 1st
    - When you drive it short distance, it generates a DTC 722 error"
    further suggestions?

  10. #10
    dieseldog
    Maybe this will help some.
    2001 Chevrolet/Geo Chevy K Silverado - 4WD
    --------------------------------------------------------------------------------
    DTC P0722
    Circuit Description
    The speed sensors are variable reluctance devices that convert mechanical motion to an AC voltage. Each sensor consists of a wire coil wrapped around a pole piece that is adjacent to a permanent magnet. These elements are contained in a housing that is mounted adjacent to a rotating ferrous member. Two signal wires extend from one end of the housing and an exposed end of the pole piece is at the opposite end of the housing. The permanent magnet produces lines of flux around the pole piece. As a ferrous object, such as a gear tooth, approaches and passes through the gap at the end of the pole piece, an AC voltage pulse is induced in the wire coil. The transmission control module (TCM) calculates the frequency of these AC pulses and converts it to a speed value. The AC voltage generated varies from 150 millivolt at low speed to 15 volts at high speed. The signal wires from the sensor are formed as twisted pairs to cancel magnetically induced fields. The cable is also shielded to protect from voltage-related fields. Using two-wire differential inputs at the TCM eliminates noise from other sources.
    DTC P0722 is a type A DTC.
    Conditions for Running the DTC
    • DTC P0716, P0717, P0721, P0731, P0732, P0733, P0734, P0735, and P0736 are not active.
    • The components are powered and ignition voltage is greater than 9.0 volts and less than 18 volts.
    • Engine speed is greater than 200 RPM and less than 7,500 RPM for 5 seconds.
    • Turbine speed is greater than 1,050 RPM.
    • The shift selector indicates a valid range selection.
    Conditions for Setting the DTC
    DTC P0722 sets when the TCM detects one of the following conditions:
    • An unrealistically large change in output speed
    • An unrealistically low output speed
    Action Taken When the DTC Sets
    • The TCM illuminates the malfunction indicator lamp (MIL).
    • When failure occurs in a forward range and shifting is complete, the transmission remains in the current range. When failure occurs while in a forward range and the shift is in process, the transmission returns to the previous range, except in post-shift state, where the transmission will continue to the commanded range. When failure occurs in other conditions, the transmission shifts to 1st, 3rd or 5th. While diagnostic response is active, if the shift selector is moved to NEUTRAL or REVERSE or any other forward range, then the transmission will lock in NEUTRAL.
    • DTC P0722 will be stored in TCM history.
    • The TCM freezes shift adapts (DNA).
    • The TCM inhibits torque converter clutch (TCC) engagement.
    Conditions for Clearing the DTC
    A scan tool can clear the code from TCM history. The TCM automatically clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without failure.
    Diagnostic Aids
    • Inspect the wiring for poor electrical connections at the TCM. Inspect for the following conditions:
    - A bent terminal
    - A backed-out terminal
    - A damaged terminal
    - Poor terminal tension
    - A chafed wire
    - A broken wire inside the insulation
    • When diagnosing for an intermittent short or open, massage the wiring harness while watching the test equipment for a change.
    • You may have to drive the vehicle in order to experience a condition.
    • If the condition is intermittent, connect the scan tool and select the speed sensor indicated by the code. If the signal is erratic, investigate and eliminate the following:
    - Intermittent wiring connection
    - Excessive vibration, such as driveline or engine torsionals
    - Irregular sensor gap, such as a loose sensor, a loose tone wheel or a damaged tone wheel
    - Inspect that the speed sensor wiring consists of twisted pairs at the rate of 12-16 twists per 300 mm (12 in). These twists must extend the entire length of the wiring harness to within at least 50 mm (2 in) of the speed sensor connector.
    Test Description
    The numbers below refer to the step numbers on the diagnostic table.
    This step tests ignition voltage.
    This step tests the wiring at the TCM.
    This step tests for proper resistance at the output speed sensor resistance.
    Step
    Action
    Value
    Yes
    No
    Schematic Reference: Automatic Transmission Controls Schematics
    1
    Did you perform the Diagnostic System Check - Automatic Transmission?
    --
    Go to Step 2
    Go to Diagnostic System Check - Automatic Transmission
    2
    Install the scan tool.
    Turn ON the ignition, with the engine OFF.
    Important: Before clearing the DTC, use the scan tool in order to record the Freeze Frame and Failure Records for reference. The Clear Info function will erase the data.
    Record the DTC Freeze Frame and Failure Records.
    Clear the DTC.
    Using the scan tool, observe ignition voltage.
    Is voltage within the specified range?
    9-18 V
    Go to Step 3
    Go to DTC P0562 for low voltage or DTC P0563 for high voltage
    3
    Turn the ignition OFF.
    Disconnect the C2 connector (RED) from the TCM.
    Install the J 39700 breakout box and the J 43799 breakout box adapter at C2 connector.
    Using a DMM, measure the resistance between connector C2 terminals 15 and 16.
    Is the speed sensor resistance within the specified values?
    2WD: 2,600-3,160 ohms
    4WD: 1,420-2,140 ohms
    Go to Diagnostic Aids
    Go to Step 4
    4
    Disconnect the wiring harness from the output speed sensor.
    Using a DMM, measure the resistance between the speed sensor terminals.
    Is the speed sensor resistance within the specified values?
    2WD: 2,600-3,160 ohms
    4WD: 1,420-2,140 ohms
    Go to Step 5
    Go to Step 6
    5
    Repair the engine wiring harness. Refer to Wiring Repairs in Wiring Systems.
    Did you complete the repair?
    --
    Go to Step 7
    --
    6
    Important: Do not rotate the speed sensor in the retaining bracket. Orientation is fixed, and if changed, may cause improper operation.
    Replace the output speed sensor. Refer to Speed Sensor Replacement .
    Did you complete the replacement?
    --
    Go to Step 7
    --
    7
    Perform the following procedure in order to verify the repair:
    Clear the DTC.
    Using the scan tool, monitor the output speed sensor operation.
    Select Specific DTC.
    Enter DTC P0722.
    Has the test run and passed?
    System OK
    Go to Step 1
    --------------------------------------------------------------------------------

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