Allison 5sp: wont downshift over 55

[fgage]

have a 2001 duramax with allison tranny. won't downshift over 55. have been to cottmen xmission, they said no codes were set nor were there any in history and they say they have no clue. just picked it up and did another road test. about 15 miles. downshifted at 60 and 65 four times, then quit downshifting above 55. any help or ideas?? getting kinda frustrated

 

[SSchmi5519]

If vehicle speed is above the value set in the TCM tuning, it will not downshift. Sounds like your is right at ~60, If I remember correctly, the OEM value there is 62mph.

 

[fgage]

got lucky got under dash and found blue wire out of tps connector that was broken. spliced back together and everything works like a champ. got myself an early christmas present