LMM - Shift Inhibited

AlRob

New member
Sep 18, 2020
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I'm at my wick's end with this and come here hoping someone could shed some light on the situation for me.

2010 GMC Sierra 2500HD - 4x4 - 155kmiles - MiniMaxx Tuner on Street Tune

Basically, a month ago my tranny slipped a couple of times between gears out of nowhere within a two day span. Was a bit annoyed but not extremely worried. Mild slips nothing major, figured I would look into it that weekend. Woke up the morning after the last slip and my truck was giving me "shift inhibited".

A month and about $1,000 later, I have installed a new TCM(DDP) and a new wiring harness. Just got the new wiring harness installed Sunday, been on the road daily since then. Until this morning when my "shift inhibited" came back. When I tell you I lost my damn mind trying to pull out of the driveway this morning.

Does anyone have any clue what else might be causing this issue? It just blows my mind to replace both the wiring harness and TCM and the truck act perfectly normal for a week just to go back into shift inhibited mode.
 

Mike L.

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Aug 12, 2006
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Is your trans stock? Shift inhibited happens when the input shaft continues to keep turning while you are at a stand still. The shaft must stop turning. If not, the TCM will not command a gear. This could be due to a pump problem, defective clutchpack, plugged internal filter, or bad turbine speed sensor. If your trans is stock; I'm betting bad clutches.
 

AlRob

New member
Sep 18, 2020
2
0
1
Is your trans stock? Shift inhibited happens when the input shaft continues to keep turning while you are at a stand still. The shaft must stop turning. If not, the TCM will not command a gear. This could be due to a pump problem, defective clutchpack, plugged internal filter, or bad turbine speed sensor. If your trans is stock; I'm betting bad clutches.
Yes the trans is stock. Ill look into the clutches.
 

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