My buddy has an '03 2500hd duramax with the 5speed alli in it. Today when we were gonna go out for a drive the truck wouldn't shift out of 1st gear and then it'd just go into neutral. If he took it out of gear and back in again it would drive for about 100ft and do the same thing over again. The message center said something about range shift prohibited. He did state that the trans fluid had been low but he filled it up now and it still does the same thing. I don't know if this was just a coincidence or not but the speedo quit workin at the same time. So any advice would be appreciated. Thanks!

My buddy has an '03 2500hd duramax with the 5speed alli in it. Today when we were gonna go out for a drive the truck wouldn't shift out of 1st gear and then it'd just go into neutral. If he took it out of gear and back in again it would drive for about 100ft and do the same thing over again. The message center said something about range shift prohibited. He did state that the trans fluid had been low but he filled it up now and it still does the same thing. I don't know if this was just a coincidence or not but the speedo quit workin at the same time. So any advice would be appreciated. Thanks!

Shift Range Inhibited, you mean? Im sure its the NSB switch....get the code(s) read.

What is the an NSB switch? Where is it located at?

Neutral/Start/Back-Up switch, and it's located externally on the transmission on the 5-speed Allisons , internally on the 6-speeds. Get the codes read, and if it requires a new one, you can get them from some of the site vendors like Merchant Auto: http://www.merchant-automotive.com/allisonnsbuswitch2001-2004.aspx

Tom

I think that the switch is also covered under the emissions warranty. Like 100,000 miles.

I think that the switch is also covered under the emissions warranty. Like 100,000 miles.

And what "Emissions" would it have to do with?

I think that the switch is also covered under the emissions warranty. Like 100,000 miles.It can be covered by the emissions warranty, though that situation appears to only be the case if the dealer feels like it. Here are some threads, though they are rather old: http://www.dieselplace.com/forum/showthread.php?t=27740
http://www.dieselplace.com/forum/showthread.php?t=27390

For as cheap as the part is, it's debatable as to whether or not it's worth messing with the dealer at all. Also be aware that there are two versions of the NSBU, a black and a tan version, with the black being the old model and the tan being the newer (and more desirable) revision.

Tom

Will both versions work?

Will both versions work?

Yes, either will work, but the tan is sealed better for water, snow and dirt- so may not have any more problem in the future, if you use the tan one. The tan one has been out for several years, so there may not be any black ones left- but you never know.:cool:

Yes, either will work, but the tan is sealed better for water, snow and dirt- so may not have any more problem in the future, if you use the tan one. The tan one has been out for several years, so there may not be any black ones left- but you never know.:cool:Yep, what he said. Both will work, but avoid the black version should you happen to come across one.

Tom

Ok thanks guys. He will have the codes read at our local dealer as soon as he gets time to haul it over there.

It ended up being a bad connection in the wires going to the speedo sensor on the tranny.

Well that's good; cheap fix.

Tom