Plowing snow and at 2 am the service engine soon light came on. I noticed that the truck was banging from foward to reverse. I also noticed that my square light around the shift PRND123 disapeared and i did not know what gear the truck was in. Drove down the road and couldent get above 50. Pulled the trans dipstick, clean no metal or burnt. Shut the truck off and started again, drove down the road fine shifting to max but is still hard to move selector. Its at GMC now. Is it the nsbu, a computer issue or is in internal? just wanted some input if the delar calls back clueless. They are a duramax repair delar but do not have and allison tec. They will not fix internal parts. If is computer related or nsbu they will fix it. i just need some imput before the next snow. Thanx:help:

NSBU or so it sounds, get a new one, make sure its tan

wait.....you say the sifter is physicly hard to move?

Also when you say it wouldnt go above 50 I am assuming the truck was running some wicked rpm?

It feel like you only had 3rd gear(harder starting out) when it was acting up?

i just did the same thing last wk, ordered nsbu from one of the vendors listed on this site, 69.00 and took 30 minutes to put on. that cured what ailed me..!!


p.s. mine was hard to go from gear to gear as well.

wait.....you say the sifter is physicly hard to move?

Also when you say it wouldnt go above 50 I am assuming the truck was running some wicked rpm?

It feel like you only had 3rd gear(harder starting out) when it was acting up?
Exactly it is hard to move. It would seem only to be in third. Was at redline at 50 mph. Hard starting out, relly have to push the gas. But after an hour of this i shut the truck off and restarted and shifted fine. Still no selector but seemed normal with a little banging.

pissed off NSBU IMO but I dont know jack

I don't know jack either, but that little POS Switch really can wreak havoc!

zippi u might of over heated the ally and or the shifer cable might of came loose

Same problem happend to me today, call the dealer it got it towed to dealer, tomorrow will know whats the problem, I hope?

I run my trans in TH when plowing and she stays cool as a cucumber. Love that TH for pushing snow.

Otheres have commented about the cable geting real stiff and others comment on breaking it.....they might be isolated problems. I've had my cabel be real stiff for a bit when I first jumped in once but it losend up. I chalked it up to a fluke. hasnt happend since. Your little black boot in tack? That whole area might have balled up with snow/ice. Been there.

Replace the transmission range switch on the side of the Allison, updated part is tan, or for half the money 4l80e range switch is same as original switch. Problem is moisture intrusion. Very Common. Hope this helps.:D

isn't this considered a warranty issue that the dealer should cover guys?

should up to 100k I believe. its considered emmison or so I remember hearing???

Hey if any one gets this covered under warranty would you post on here and let me know.I had the same problem last month and it was the NSBU switch,my truck is an 02 and has under 60 K on it.The gangster at the dealership who goes by the alias "service manager" told me that he had consulted GM and they would not cover this under warranty.

Dammit...........you guys bring this stuff up, and somehow my truck reads about it.
Starting today, the little square box doesn't illuminate in N or 2. Takes about 5 seconds after starting to illuminate P. I don't think it's done that before. Then after a quick test drive to make sure it runs & shifts OK.....put it in Park, and no box there.
Hope it holds out intil I can get my hands on a replacement!!

Call Eric. He has em.

If your NSBU switch starts freaking out sometimes cycling through the gears P to 1 a few times and sometimes restarting the truck will wake it up......or it did on mine 2 times before i got it fixed.

Got it fixed, dealar said it was trans control? Seems to runnin alot smoother.

NSBU switch it is 3 days later problem was located and solved, good thing there was no snow, but all done under warranty 3/36 still,