trans problem.

[GMC-ya!]

hey guys, im once again counting on someone that knows what they're talking about to help me out so I came here. Ill try to include every detail so this post might get long. I was leaving for work today and the truck was running fine. I went to throw it into D and it wouldnt go into gear. I sat there for a moment and tried it again and it went in. As I took off down the road the truck popped into neutral I believe, and the SES light came on. I got turned around and got the PPE (only thing i have) to check the codes, cleared them and drove 20 miles to work just fine. At work I crawled underneath the truck and saw a 50 pound block of ice covering the trans and transfercase. I spent about 45 minutes chipping it all off. Drove the truck around the parking lot and everything was perfect. The truck sat for 7 hours and when I went to leave it was stuck in limp mode. I once again pulled the codes with the PPE. I left it at work so im going by memory here, but I got a 0700, 0722, 0872, and 0875. Couple other things I noticed was the shifts from Park to anything really, were harsh. The indicator light wasnt on half the time I was screwing with it, and when I put the truck in park the doors wouldnt automatically unlock like usual. Is this the NSBU switch going out that Ive heard about so much in the past? I guess I'll try to search it but its 11pm and I have to work at 6am so I want to get some sleep. I usually dont post at all in the transmission sections of forums but i need some help and I figured this would be the place to get it. Thanks everyone.

 

[wes06dmax]

I have a friend who has a 02 and he can be driving with his stock tune and the truck limps I have got 7 codes 0700,0722,0735,0708,1711,1713 I clear his codes and his does fine for about 20 miles then it limps again and he doesnt even know it till he stops and goes to take off again but I figured his problem was that the alli has 250,000 miles on it and he has limped it about 20+ times just figured it was time for a build but you could be on to something yall could have the same problem hope Mike L read this.

 

[GMC-ya!]

Thats what Im hoping for. Ill admit I limped mine one time in the rain and I wasnt really doing anything stupid. when I did a vin check I dont recall the switch ever being replaced so I was hoping that was all the problem is.

 

[ferramento]

Sounds exactly like what my work truck (07 LBZ 120k) did. It would not shift with the selector in D but if I pulled it into M and selected up to 6 - it would get me where I needed to go. Sometimes it would throw a code - sometimes it wouldn't. Some times it would say range inhibited on the display and other times it wouldn't. Drove it for a week like that. The doors won't unlock because the trans isn't sending the signal that it is in park. Changed out the NSBU - first time and only took about an hour - never had a problem since. Than is on a 6 speed. I've heard that with the 5 speeds it is an external part and you don't have to remove the valve body from the tranny - lucky.

 

[GMC-ya!]

I hope thats the case. I wanted to use a better scanner but I was about 30 miles from my brothers shop so I used what I had to get any info. Like I said, I dont post in the tranny sections a lot but I do scroll through them. I remember a while back over at the place when this seemed to be a pretty big problem for people so I figured now its my turn.

 

[wes06dmax]

I had another friend call today with a 01 and his trans is hung in first gear will not shift and he took it to a trans shop they said that a sensor had went bad but they wasnt 100% for sure dang is the cold weather making the stock allisons tap out lol

 

[Mike L.]

Sounds like an NSBU problem.

 

[x MadMAX DIESEL]

Don't know about the codes to verify. But the only time mine has ever poped out of gear is when the truck is in too high of a gear (like messing around with the dvt tab)

 

[GMC-ya!]

Well guys, I got off of work too late this evening and every place was closed. The dealership wanted 140 bucks but ive heard they can be had for about 50 bucks so I left the truck at my brothers shop. We took the NSBU switch out and tore it apart. Sure enough there was dirt and condensation all over inside of it. We cleaned it out really good and dried it with the air gun. After reinstalling it, the truck ran like normal so Im just going to pick up a new one tomorrow afternoon. Thanks for the help. I read earlier that ice, snow and slush can cause these to go bad??? can anyone clarify that?