allison 5 speed won't go into 5th gear

[fixit]

i have a 05 monaco and my check trans light comes on and when it does my trans will notupshift up to 5th gear. i have had the tcm and the ecm checked. the ecm says im ok but the tcm says when iwant to upshift i am asking the engine to slow down a little and the tcm gets no response? so the tcm won't shift to 5th. gear
Go figure?
Any clues?

 

[dbarton291]

RE: allison 5 speed won't go into 5th gear

fixit - 6/2/2010 2:38 PM

i have a 05 monaco and my check trans light comes on and when it does my trans will notupshift up to 5th gear. i have had the tcm and the ecm checked. the ecm says im ok but the tcm says when iwant to upshift i am asking the engine to slow down a little and the tcm gets no response? so the tcm won't shift to 5th. gear
Go figure?
Any clues?

What's the diagnostic code list in the TCM read out? If you had it checked out, that's the first thing the technician should tell you.