I had originally posted this as a reply to another thread regarding trouble shifting into high gear on an Allison transmission, but decided that the topic was sufficiently different to warrant a new thread. Apologies if this has been covered elsewhere and I failed to find it.

I started having similar problems to the ones outlined in other NSBU-related posts, but I also have a couple of other nagging issues that may or may not be related to the nsbu (bought one yesterday, $55, have not installed it yet). If anyone can tell me if these are nsbu-related, I would appreciate it.

Background:

Eight weeks ago, noticed that right front wheel was not pulling when in 4WD. Intermittent. Pulls sometimes, sometimes not.
Four weeks ago following snowstorm, notice hard "clunk" when shifting from Reverse to Drive. Only happened once.
Two weeks later, Cruise would not engage. Shut off engine and restarted, problem went away.
Four days ago, shift "clunk" happened twice when shifting from R to D. Also, when putting transmission in Park, doors had to be manually unlocked (should be automatic). Unlock problem persisted all day.
The next morning, SES light came on, stayed on after restarts. Was annoyed by the door unlocking problem still present, so when I got to my shop, I worked the shift lever between P and R several times (position indicator under PRN was missing). Message center displayed "Range Shift Inhibited", and then the doors started unlocking again on shift into P. No further PRND321 problem since, but again today right front wheel would not pull in 4WD-H or 4WD-L.

I'm pretty sure that replacing the nsbu switch will resolve the door lock, shift clunk, PRND321 indicator problems, but does anyone know if the nsbu can affect the Cruise Control or (more importantly) the front wheel not pulling when in 4WD?

2003 Silverado 2500HD Duramax 4x4 LWB with Allison 1000-series trans., 101K miles, only been in 4WD 10-12 times, not driven hard or romped.

Any replies appreciated.
Fraggedout