Duramax Diesels Forum Truck of the Week
Old 10-18-2019, 04:35 PM
Stephenj3 Stephenj3 is offline
Join Date: Oct 2019
Location: Canada
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Default 04.5 Allison problem

Hi all, first post so forgive me for any mistakes! So a few days ago, my transmission suddenly stopped registering in park. The line under P wouldnt come on and the truck acts as if its in gear (doors wont auto lock/unlock door chimes when doors are open). I got under there and sure enough the cable and NSBU I think its called were looking fine. I had someone move the lever into all positions and the switch on the side of the transmission responded accordingly.

And as of today it wont register in P R or D. Only in N 3 2 1.
It does however work fine, all 5 gears work and so does drive and reverse, it just doesn't register or show the lines under the gear selected other than N 3 2 1. My CEL came on and the SHIFT RANGE INHIBITED message pops up occasionally while flashing under 3. Where do I start with diagnosing this? I dont have a code reader on hand and will probably head to a trans shop after some feedback. Its a 2004 LLY. Thanks!!
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Old 10-18-2019, 05:05 PM
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TheBac TheBac is offline
Why do I keep doing this?

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Moved to Mike's Trans Talk section.
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Old 10-18-2019, 05:29 PM
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Tothemax Tothemax is offline
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most likely a range switch
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06 lbz ec/sb. stock motor, Danville 4094s2r, built trans by me, limitless 1078 converter, 60% sticks, S&S 12mm pump. dyno tuned by mark @ Danville. 775hp 1383ftlb

best so far. 11.440 @ 118.12 1.623 60ft

06 lbz rc/fb dually work truck. Danville tuned
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Old 10-18-2019, 06:00 PM
Stephenj3 Stephenj3 is offline
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Is that an easy fix?
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Old 10-18-2019, 06:48 PM
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Mike L. Mike L. is online now
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It's called a NSBU switch. First thing to do is replace it. Problem may go away.
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