Allison gear position switch

[ALLIMAX]

I had a gear position switch on my Allison stop working yseterday. The transmision locked into 3rd gear and would not shift out. I first noticed it going out when the gear indicator lights in the dash did not show what gear it was in. Soon a service engine light came on and that is when it locked into 3rd gear. It would still go into reverse however. THe dealer stated that he had replaced several of these in the past and that the new ones were upgaded. After installing the new switch and reprogramming the tranny computer all is well. Has anyone else had this problem? Mine is an early build 2001.

[hoot]

I did a search on "nsbu". There are others too.

http://forum.62-65-dieselpage.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=7&t=002632&p=

[Brad Pelot]

I am currently awaiting the very same switch. Mine is stuck in 3rd as well.

[77TransAm]

Just a heads up to let your dealer know about...

The old switch (the one that tends to fail) is one that GM has used for years and most dealers have in stock. A lot of dealers just reinstall another one of these, and you're just as likely to have another failure as before.

Allison has released a new (and much improved) switch and it is available, but most GM dealers don't stock it yet. If you can convince your dealer that you'd rather have the new switch on your truck, you're MUCH less likely to experience another failure.

Old switch p/n: 12450016 (black in color)
New switch p/n: 29540479 (beige in color)

[ 04-24-2002: Message edited by: 77TransAm ]</p>

[DetroitBob]

AlliMax. Check with an Allison or heavy truck dealer (if they service Allison trans) for the part
you may luck out.

BoB

[Brad Pelot]

About a week ago it snowed 14 inches here on a monday. Within the next 24 hours at least 5 of these switches have gone out at the the dealership that I work with alone. All of these were early 01's.
My parts just came in this morning, and I am up and running. I hope this is the improved switch. I suppose it would be where they overnighted it in, since they were out.

[Turbo Al]

I was in the middle of nowhere when mine died. I crawled under the truck in the snow & mud and found the wiring harness was hanging out of the switch. So I suggest you check out the harness and maybe plug it in and out a couple of times.
It's on the Driver's side, on the trans beside the front drive shaft, it's the larger (upper) connection and it is held in by a blue plastic safety pin in the clip. Clear as mud -- I know.