Allison 5sp: neutral safety switch problem?

AubleAK

New member
Aug 5, 2011
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Glennallen, AK
drove to napa to pick up some tools yesterday afternoon, came out 15 minutes later and when i put the truck in gear, none of the gears lit up, and it wouldnt go over 40. pulled over, cycled the key three times, still same thing. no codes. after that i stopped by another place to talk to my buddy, and left it running for 10 minutes, came back out, all was well.

8 hours later, after sitting in the cold, ran to the gas station, (let the truck warm up about 10 minutes) and everything was fine. pulled up, put it in park, kicked on my high idle, and about 3 seconds later the high idle kicked off. looked down and none of the gears were lit up, and a service engine light was on. threw the codes -

p0708 - Transmission range sensor circuit high input
p0700 - Transmission control system
P0093 - Large fuel leak? Looked everywhere, no fuel leak.

im guessing the neutral safety switch, but i wanted to know what you guys think before i go spend $200 on a new one!
 

madmatt

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Apr 12, 2009
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drove to napa to pick up some tools yesterday afternoon, came out 15 minutes later and when i put the truck in gear, none of the gears lit up, and it wouldnt go over 40. pulled over, cycled the key three times, still same thing. no codes. after that i stopped by another place to talk to my buddy, and left it running for 10 minutes, came back out, all was well.

8 hours later, after sitting in the cold, ran to the gas station, (let the truck warm up about 10 minutes) and everything was fine. pulled up, put it in park, kicked on my high idle, and about 3 seconds later the high idle kicked off. looked down and none of the gears were lit up, and a service engine light was on. threw the codes -

p0708 - Transmission range sensor circuit high input
p0700 - Transmission control system
P0093 - Large fuel leak? Looked everywhere, no fuel leak.

im guessing the neutral safety switch, but i wanted to know what you guys think before i go spend $200 on a new one!

no need to spend $200 either. Go to the Allison dealer or i think Napa has a cheaper replacement. Also for your area where snow build up may be an issue GM did offer a shield that covered the NSBU switch to prevent just that. may wanna look into it.
 

snowman

Evil Diesel Performance
Aug 30, 2010
350
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Manitoba Canada
had those same codes on a buddies truck and it was the NSBU switch.

X2 on going through allison, alot cheaper. I think i payed $90 for my buddies.