The nsbu swith is inside my trany. I think it has somthing to do with the shifter safety?? The truck is an 06 D-Max with the manual shift on the shifter.

the problem i am having is that my truck wont start and no light on the dash for my shifter but the rest of the dash lights work. the truck thinks it is not in park and wont start battery is also fine. will not start in park or rev

Yes, starting in 2006 the Allison went from a NSBU to an internal mode switch (IMS) inside of the transmission.

Did you jump start your vehicle recently? There have been some cases of people touching the transmisson module accidently while hooking up the jumper cables to the battery terminals. If this happens it blows out one of the ground circuits and basically fries the trans module. All you can do in that case is replace it. The later ones came with a plastic shield to give it some protection.

If that's not it, the IMS has a circuit going to the ECM that tells it if it's in park or neutral and safe to start. If you have a multimeter you can check pins R and H at the 20-pin connector on the transmission. That circuit should be closed when in park or neutral and open the rest of the time. If it's not that's your problem.

Thank you