So, I was leaving my girlfriends apartment today. I went out and started up my truck (in sig) and proceeded to back up and leave. I noticed that when i cranked it the SES light stayed on and its never done this. When i shifted to reverse, the indicator light that lights around the letter of the gear your in (the light around "R" on the dash) flashed once it was in gear. I shrugged it off and backed up and left. It didnt seem like it started off in 1st gear once in drive. It seemed to be 2nd or 3rd gear. It would stay in that gear and not shift up or down. After checking the fluid and laying on the ground and checking the the tranny for obvious loose connections i found nothing. I turned the key to the on position and pumped the gas 3 times and turned it off. I then turned it to the on position again and hit the brake 3 times. I wasnt sure what i was trying to accomplish but it worked. After i did that and took it down the road it was shifting just as smooth as it had been although the SES light was still on. Any ideas on what could have made the tranny do that and then kind of "fix" itself?

Thanks
-Kody

It's highly possible your NSBU switch on your transmission is going bad. If you look under the driver's side and at the side of the tranny, you should see it with the shifter linkage and a plug connection. If it's black, you have the original one and it was bound to take a dump. If it's tan, it's the new version. It's easy to change. I don't recommend buying it from the dealer. You could order it on here from a supporting vendor way cheaper. Good luck!

Alright. Thanks. I will go check to see which one it is.

Its black and has 2 plug connections. Where can i buy this from?

Check for an Allison dealer or I think you can get it at www.merchant-automotive (http://www.merchant-automotive) .com. This link was listed in my Allison filter thread and, if I remember right, they had the switch.

Alright. Thank you very much!

-Kody

I was going to order mine from Merchant, but a guy PM'd me and said that he had a spare he kept under the seat and was trading in the truck so he didn't need it. It's been fixed ever since. Glad we could help you out!