2003 Allison no forward gears

[Lb7puller]

One day I was driving around town and stopped at a light. When i went to take off from the light i had no farward gears only reverse. Took it to a shop and they said the tcm was fried. Put a new tcm in and still no forward gears. Next was a full trans rebuild including a suncoast converter. Still no forward gears. Just started replacing parts after that. Here’s the list of new parts: tcm, full rebuild, torque converter, valve body, pressure switch, internal harness, and nsbu. Still no forward gears only reverse. Need help. No codes.

[DmaxStoreAustin]

Ok im going to try to unplug everything tonight and see if i have 3rd gear or not. Thanks for the help.

Lb7puller,

Did you get it figured out?

[DMAXDR]

Ok im going to try to unplug everything tonight and see if i have 3rd gear or not. Thanks for the help.

No problem, let me know what you find.

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[Lb7puller]

Ok im going to try to unplug everything tonight and see if i have 3rd gear or not. Thanks for the help.

[DMAXDR]

Seems like C1 is not applying, was C1 clutch air checked when the trans was being rebuilt?

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Also ,if the TCM is completely disconnected the trans should have 3rd and reverse by default with no electronics. If 3rd is not obtained then C1 clutch is suspect. C1 and C3 are used for 3rd and C1 and C5 for first. C3 and C5 for reverse.

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[DMAXDR]

One day I was driving around town and stopped at a light. When i went to take off from the light i had no farward gears only reverse. Took it to a shop and they said the tcm was fried. Put a new tcm in and still no forward gears. Next was a full trans rebuild including a suncoast converter. Still no forward gears. Just started replacing parts after that. Here’s the list of new parts: tcm, full rebuild, torque converter, valve body, pressure switch, internal harness, and nsbu. Still no forward gears only reverse. Need help. No codes.

Seems like C1 is not applying, was C1 clutch air checked when the trans was being rebuilt?

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