Duramax no reverse......

[SlickWillie]

Well, I shift to reverse the other day, and I get "range shift inhibited" on the DIC. No reverse. After researching the problem on a couple diesel sites, I believed the problem to be what is referred to as the "NSBU" switch on the tranny. I also read it was part of the emissions system, and should be covered as such. We're in Port Mansfield, TX, so I called around and the GMC dealer in Brownsville told me to bring it in. They didn't have the part but should have it tomorrow and will install Wednesday if I can limp it back over there. I had a he11 of a time convincing the service writer it was an emissions component, but I was determined, and finally succeeded. If you should have this problem, argue, argue and argue some more if they don't want to cover it under the emissions warranty. You'll probably be out at least 300 bucks if you don't.

[Steve and Brenda]

Thanks for the input amigo, goes against logic though. I'm still trying to figure how a drive train issue is related to emissions.

[Montana Sky]

Will,
I read this problem on the dieselplace.com web site all the time. Keep us updated on the outcome...

[rvghostdriver]

quote:Originally posted by Montana Sky

Will,
I read this problem on the dieselplace.com web site all the time. Keep us updated on the outcome...

Isnt this the allison transmission? Not so bulletproof I guess. None of them are.

[SlickWillie]

quote:Originally posted by rvghostdriver

Isnt this the allison transmission? Not so bulletproof I guess. None of them are.

It is actually a switch that mounts externally at the gear selector on the tranny. I don't know if it is an Allison or GM supplied part. From what I read on a TSB on some of the earlier models, it is subject to getting water spray in the switch, especially on left turns (front tire spray). I'm not convinced anything mechanical is "bullet proof".

[snowbunny]

I know there was a thread on this about a year ago.

I had the same problem about two years ago. I park my Chev D/A nose in in my garage. One day I went to back out and had no reverse! It would go in forward but not reverse. At some point I turned off the engine and later tried it again and everything worked as it was supposed to. I went to my Chev dealer and he asked me how long the truck had been sitting as it was something that sometimes happened when they weren't used for a while. It had been a few weeks in my case.

Anyway, I haven't had any problems since (knock on wood!)

[SlickWillie]

OK, here's the final chapter. I still had trouble after the "NSBU" switch was replaced. I took the truck to Neessen GMC in Kingsville, TX. Long story short, it turned out to be the ignition switch. If I understood the mechanic correctly, there is a switch that provides voltage to the tranny, and that switch had bad contacts, providing low voltage. After installation of the new switch, everything works like new. I strongly recommend the folks at that dealership. I know how hard intermittent problems are to locate, and the mechanic was able to diagnose the problem quickly.