after installing my new tranny with the gmax6 pack. the truck is stuck in 3rd and is giving me trouble with the shift range inhibited.....does anyone know what could be wrong?
AHH help...new tranny stuck in 3rd
- Thread starter Builtlngbd
- Start date
The Allison Diagnostic manual lists P0877 as "Transmission Reverse Pressure Switch Circuit Stuck Closed". Do this: Start the truck, put it in Neutral and clear the codes. Put it in Drive and see if it seems to behave normally. If it does, put it in reverse. If it flips out and sets the code and range inhibeted when you place it in reverse, the O-Ring for the reverse pressure switch is likely missing or out of place. I don't remember what code I got, but this was the behavior I got when I put the PSM back in and didn't watch the alignment of the O-Ring closely. Going from Park to Drive had the trans in reverse long enough for it to flip out. Pulled the PSM and sure enough, the O-Ring was out of place.
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oka so ive been on the phone with sun coast alll day long working on this problem. the o ring on the pressure switch was on there and installed correctly. Long story short we are leaning towards maybe the pressure switch OR the switch that goes by the shift rod that come out of the tranmission. It may not be working hense the shift indicator light blinks. i might just replace both and be done with it. ill keep yall in touch on what i find.
make sure that conector is plugged in good, i broke my retainer tab things off my connector (the one that goes into the PNRDL witch) and i had to run a bit of silicone where the connectors meet to keep it from unplugging a bit and having the shift indicator light disappear
Did you have the valve body apart? Any chance you got one of the valves installed incorrectly? Shift range inhibited means the TCM see something wrong like massive loss of pressure. Did you do the build or someone else?
Have you tried what I suggested and/or pulled the pan & PSM and verified that the O-Ring is in fact where it belongs? When I had my issue, I was "sure" it was right. It was the second trans I had built and probably the 6th time I'd worked on an Allison VB, but it managed to slip a little when I was installing the PSM.
yes i did remove it and reinstalled it about as slowly and carefully as possible. and i did not rebuild the tranny i had a diesel shop do it
oka so i replaced the pressure switch and that fixed it! not sure if is was the oring or the switch. so i just replaced the whole thing. Thanks guys for all the input yall gave me