Help Tech guy's! NSBU Switch problem ?

[cowboywildbill]

While driving in the snow this week, my allison started to act funny. No codes were displayed. When I stopped and placed the truck in reverse, the display would stay in the "D" position for a second or so and then move to the "R" position by itself, and then clunk the truck would go into reverse kind of hard. It seemed to drive and shift ok otherwise. I parked it and had my allison dealer order me the new style switch. He said it is now a kit and comes with a harness to adapt it to the truck? They couldn't find any listings for the NSBU for specific models, like GMC. What do you all think think? Does it sound like a NSBU problem? I am waiting for the parts! Thanks.

[77TransAm]

Allison has an even newer NSBU than the tan one. It is a completely new style and uses only one big connector instead of two smaller ones. I didn't realize it had been released to GM yet, but if that's what you're getting it sounds like good news for you.

From the Allison Service Information Letter:

Effective July 2003, Allison Transmission will release a new NSBU switch assembly, P/N 29541852. The new NSBU switch assembly utilizes a Delphi-Packard style 12-pin single connector that incorporates a sliding cam lock. The new switch allows all NSBU related wiring to be incorporated into one single connector. Other improvements added to the new NSBU switch include an internal neutral alignment shear pin and a splash shield that is retained to the switch housing. The new switch assembly also incorporates improved sealing qualities making it more robust to external elements.

[cowboywildbill]

That sounds like the picture they had of the new switch. But I am still waiting on it. I am wondering if the problem I am experiencing is related to the switch? Has anyone else had simular symptoms? With the delayed shift into reverse and the display moving on it's own? I haven't had any other problems, I think if my tranny was going bad, it would have slipped or done something else before this point!

[Buckman]

Cowboy:
The NSBU switch part number that your Allison dealer needs to obtain for you is 29540479. That is the "tan" switch which includes the switch and a shield. The single connector switch "CANNOT" be adapted to a truck which previously had the two connector style switch. Sounds like you're on the right track to resolve the problem. Have a great holiday season.
;) ;)

[cowboywildbill]

Thanks for the response, I got the tan switch today and will try and put it on tommorrow. I started the truck today and it did the same thing, and then it wouldn't go into reverse or drive, but the display moved sometimes. Then when I put it in drive, it felt like it was in 2nd or 3rd gear. I checked the fluid and it was down just a little on the cold mark. I added some but I don't think it was low enough to be the problem. I noticed that the fluid still smelled sweet "I did the transynd and deep pan thing last summer" but the fluid was a little more on the brownish red side, than the bright new red transynd I added. I am hoping that it is normal to discolor a little over time. I did notice after it wouldn't move on the first attempt today, the service engine light came on. I guess I'll find out tomorrow if the switch will do it. I'll let you know how it does. Thanks again for your input.

[77TransAm]

Transynd does change colors to a more brownish-orangish color than you would expect to see in transmission fluid. It happens in all the transynd trucks I've seen and seems to be normal - certainly doesn't seem to affect fluid life.

[DMAX4LIFE]

You said that this new style switch CANNOT be adapted to an older truck? Is there any way to convert the tranny or switch so we can avoid all the problems with the NSBU switch?

[ 12-11-2003, 08:40 AM: Message edited by: DMAX4LIFE ]

[cowboywildbill]

Yes Sir! It must have been my problem. I replaced the switch this morning in 40 knot winds,laying outside. It was an easy job, except for the bigger plug, which was glued into the switch assembly with some kind of hot glue sealer. It took me 10 minutes of prying and finesing to get the the plug out of the old switch without damaging the plug. And then 10 minutes of picking the glue out of the pins in the plug. Thanks to all of the advice on the forum, I had a good idea that maybe this was the NSBU problem because I had read about it here, and the fact that it happened after running around in a snowstorm also when it acted up. Strangley enough, it seemed to work somewhat OK this morning when I started the truck to drive it up on the ramps. It was windy all night, maybe it dried the old one out or maybe they come and go. Any how I got it installed and it seems to be doing fine, I ran it about 50 miles start and stopping several places doing errands and getting feed for the livestock. The service engine light went out after about the 3rd start cycle and didn't come back on. I got the tan switch as the replacement $45.00 and I will get a spare also.I had a chance to look at the new style switch at the allison dealer, it looks like it could work if they made a pigtail two into one connector for it. The present NSBU switches have the same number of pins using two connectors as the new style does, only it has all of them in one bigger connector. So I wonder if a jumper harness would work? The new style switch is a lot better looking as far as being sealed from the elements. It has the shield molded in. Thanks again for all of your input. Now I can sleep tonight knowing that It isn't the tranny. Keep up the good work and THANKS SO MUCH!