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Thread: Allison trans issue

  1. #1
    Join Date
    Apr 2018
    Location
    Front Royal, VA
    Posts
    30

    Default Allison trans issue

    Hello All,

    I have a 2003 LB7, on Monday I was driving on the highway at about 72 MPH with the cruise on. Fairly flat area and it felt like the truck downshifted. I looked over at my CTS3 and the rpm's were up a couple of hundred and the gear selection was only showing being in 5th gear. Normally it shows 5 TCL. After a couple of miles the TCL came back on and the torque converter locked back up. The rpm's also came back down. It did this three times during about a 45 mile drive on the highway. The truck has just under 180,000 miles. Trans cooler and lines were replaced last June. Fluid recently checked and all was good at that time. I am a field tech by trade, so the truck is probably over maintained by some standards. Any suggestions would be greatly appreciated.

    EFI Live 0-90 hp tune
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    Ryan's Diesel 64mm Supercore Turbo
    Banks exhaust and cold air intake
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    PPE trans cooler and lines
    FASS
    Stock height with Kryptonite upper control arms and ball joints
    2003 Ext. Cab Long Bed
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  2. #2
    Join Date
    Apr 2018
    Location
    Front Royal, VA
    Posts
    30

    Default

    Could this be a solenoid issue???
    2003 Ext. Cab Long Bed
    Banks Cold Air
    Banks Exhaust
    SAC injectors
    EFI Live Tuning

  3. #3
    Join Date
    Jan 2001
    Location
    New Hampshire - Live Free or Die
    Posts
    6,113

    Default

    Could it be something simple, like brake pedal return spring allows pedal to sag and hit the brake light switch?
    The Constitution needs to be re-read, not re-written!

    If you can't handle Dr. Seuss, how will you handle real life?

    Current oil burners: MB GLK250 BlueTEC, John Deere X758
    New ride: MB GLS450 - most stately
    Gone but not forgotten: '87 F350 7.3, '93 C2500 6.5, '95 K2500 6.5, '06 K2500HD 6.6, '90 MB 350SDL, Kubota 7510

  4. #4
    Join Date
    Apr 2018
    Location
    Front Royal, VA
    Posts
    30

    Default

    Thanks JohnC, I will look into it over the weekend.
    I do like your signature.
    2003 Ext. Cab Long Bed
    Banks Cold Air
    Banks Exhaust
    SAC injectors
    EFI Live Tuning

  5. #5
    Join Date
    Apr 2018
    Location
    Front Royal, VA
    Posts
    30

    Default

    The more I think about it, if the brake light switch was being even remotely activated. The cruise control would have disengaged and that did not happen. I now have an Allison service manual from 2000 that shows "Solenoid F" as being the converter clutch solenoid. I recently saw a YouTube video were fluid was leaking into older Allison's solenoids causing issues. Maybe I should just check the external connectors for trans fluid. I don't think it will hurt.
    2003 Ext. Cab Long Bed
    Banks Cold Air
    Banks Exhaust
    SAC injectors
    EFI Live Tuning

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