Posting this for a friend. He has an 03 2500 duramx/allison with 145000 miles and it has an Edge juice box under the hood thats all for mods. Every so offen when he puts it in reverse it won't go anywhere and the message center on the dash says Range Select Inop or something like that and he has to shut the truck off and restart it then it might work fine. And also where the gear selector display doesn't light up at all ever. Would that have something to do with it not shifting? I have never worked on a Chevy and this is his first diesel.
Sounds like the NSBU switch is going out on him. It is a semi common problem on these trucks and will cause it to not go into gear, gear display won't read, and it will display range shift inhibited. It is the switch that is on the gear selectro shaft that goes into the trans. Also don't buy the switch from GM, but find an ALLISON dealer to get it from. It will be the same switch for half the cost. Just give them the serial number off the trans and they can look it up for you as 03 can be either the early 2 plug or the late single plug style.
ok we changed the NSBU and I fixed a wire that was about to break. The truck was fine for about a day or so but he said it still does it and the gear selector still isn't lit up. any other ideas?
change your filters there is one inside that you'll have to drop the pan and change the spin on. when you change the spin on there should be a magnet at the top of the threads where it spins on. you want that magnet dont lose it. change the tranny fluid and go with synthetic fluid.
I don't see what a filter change is going to do it seems like a electrical problem to me.
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