Allison 1000 series

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Tinman1956

New member
Joined
Aug 2, 2019
Posts
2
I recently purchased a 2003 Monaco with a 1000 series Allison transmission.The second time out with it I experienced problems with acceleration which I now know is due to transmission staying in third gear.I believe the problem is due to nsbu switch which was changed by previous owner.Sometimes it would not start and would not go into reverse and would set check transmission light,so I adjusted switch slightly and everything was good for a little while then it started doing it again.I am going to change nsbu switch my question is are all nsbu switches for 1000 series with 2 plugs the same or are there different ones .
 

SpencerPJ

Well-known member
Joined
Nov 1, 2017
Posts
4,029
Location
Midwest
This seems to be a good link of interest.  It seems there is only 1, with 2 plugs
https://www.dieselplace.com/forum/57-gm-transmissions/41-allison-oem/338137-nsbu-replacement-instructions-faqs.html

I certainly would not buy off Ebay for a great price, I'd stick with OEM.

https://www.dieselplace.com/forum/57-gm-transmissions/41-allison-oem/338137-nsbu-replacement-instructions-faqs.html
 

Jhcowdude

Well-known member
Joined
Jul 12, 2018
Posts
45
Location
Douglas, Wyoming
Going through something similar with an 03 Duramax I just bought. Empty, worked great. Put in a bind or hard pull, would throw a code and take away reverse. When it cooled down, I could clear the code and get the trailer backed in where I wanted and unhooked. Thru lots of reading, I learned it was the F solenoid inside the transmission. Having it fixed right now. Seems to be a fairly common problem. I think in a pinch, it could be done in the driveway, but having a pro do it due to some other stuff. Gets the codes checked, might be something fairly easy. The Allison's will work a long time, but insist on good maintenance.
 

Tinman1956

New member
Joined
Aug 2, 2019
Posts
2
Was told by previous owner all fluids and filters were changed 500 miles ago and look good,filters also look new.Don't think that's a problem.nsbu switch looks like it has been adjusted several times.I don't know how switch is attached to the shaft,but I have ordered a new switch and will change it.I don't know if I have to clear codes and reset check transmission light or if it will do it once everything is fixed.Check transmission light was going off after restarting.Thanks for help on switch and information.
 

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