Help , trans problem

chevygal21

New member
Nov 18, 2009
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I'm new at this and not so good with computers, so I had a Trany problem, and just see'n if someone could help, Thanks have a good day!
 

TrentNell

Finally underway !!!!!
Jul 7, 2008
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I moved your post to the trans section , hope you get some help . In order to help you we need a description of the problem , and any codes involved if it popped a check engine light .
 

chevygal21

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Nov 18, 2009
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Well, the check engine light comes on, and when you go to stop fast it just shifts down hard(bang)! No codes comen on. It seems to not want to shift down all they way, and sometimes it won't even go into gear when I go to take off!
 

chevygal21

New member
Nov 18, 2009
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We had trany flushed and filters changed, we changed fuel filter, thermastats, cool temp sensor.
 

McRat

Diesel Hotrodder
Aug 2, 2006
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Mike L. is the Obi Wan Konbi of the Allison, (but he looks like Yoda). Hopefully he sees this thread.

Harse downshifts and not full trans operation sounds really familiar. Neutral Safety Switch?

Tell us the year of the truck, mileage, and any modifications you have done.
 

chevygal21

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Nov 18, 2009
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2001, 191,000 miles, none, and a chip that has never worked ever since we bought the pickup 6 months ago.
 

McRat

Diesel Hotrodder
Aug 2, 2006
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If you can't read the codes, the neutral switch is a common problem on that year, and is not expensive if you buy it at an Allison dealer. It's on the driver's side of the trans.

NSBU is it's name. Do a search here on NSBU and see what you find.
 

Mike L.

Got Sheep?
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Aug 12, 2006
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Get the codes read before you start throwing money at it. Remove the chip and see what happens. Possable NSBU problem or spin on filter problem. The clunk is telling you the computer sees something it doesn't like and has gon into a different strategy.