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Topic: Allison transmission problems

Posted By: thelonius on 01/28/07 02:10pm

I have a 2005 GMC 2500 Duramax Crew Cab pickup. Lately, whenever I put the truck in reverse, the line under the R will blink and the message center says "shift range inhibited". I've taken the truck to my dealer and they replaced the switch in the steering column. Brought it home and in a couple of days, same thing, no reverse. If I put it into drive, it slams. Took it back and they replaced the transmission control module. After a few more days, same thing. Now the truck is in the garage for another major part change. Has anyone ever had this problem? Sure glad this is happening in the winter. I'd really be mad during camping season and towing. Any thoughts would be appreciated. My dealer doesn't know what to do and GM wants to try all of these parts before they replace a transmission. That hasn't been talked about yet, but I'm getting to the point where I'm going to suggest it real quick.

2005 Duramax GMC CC
Jayco Designer 4 slides 35'
Pullrite Superglide 16K Hitch

Posted By: floridacamper on 01/28/07 02:27pm

Your signature says that you own a 2001 Dodge ram 2500 V-10, HeHeHe


Posted By: thelonius on 01/28/07 02:45pm

Sorry, I've changed my signature to the correct vehicle. Thanks.

Posted By: 32dgrz on 01/28/07 02:55pm

You might try posting at this forum. They have been a lot of help to me
Diesel Place Allison forum

Posted By: Butch50 on 01/28/07 04:43pm

Sounds like it is the switch on the trans going. I forgot what they called it, something like the NTS (I'm sure someone here can help me out on this) In the early years of the Dmax/Allison there was some trouble with these switches. I had a 2002 3500 and read about these switches but never had any trouble with mine.


I try to always leave doubt to my ignorance rather than prove it

2017 Ram 3500 Mega DRW
2018 Grand Design 303RLS

Posted By: bluenote on 01/29/07 10:51am

It sounds exactly like an NSBU (neutral safety back up) switch gone bad. Check with your dealer on a warranty replacement. On the diesel trucks, it is covered under the emissions warranty, not the basic warranty. I got the one on my 2001 replaced under warranty at over 90K miles because the emissions warranty was 100K for that model year.

Posted By: ib516 on 01/29/07 12:25pm

Not the same problem, but a buddy of mine has a 05 Duramax/Allison crew cab 4x4 2500HD. He has 25,000 miles on it, and it gets used mostly as a car, occasionally pulling a heavy trailer (not an RV). He told me that he discovered a puddle of trans fluid under the truck, took a closer look and found the whole undercarriage of the truck soaked in ATF. Took it in to the dealer for warranty work. They discovered that the tq converter bolts had come loose and allowed the tq converter to become sloppy in mating with the engine. This damaged the seal, and allowed the oil to leak. I haven't heard of this happening before.

I have heard of the NSBU switch issue before though.

Generally speaking, Allison transmissions installed in the GM 2500/3500 trucks are not known to be problematic.

Prev: 2010 Cougar 322QBS (junk)
02 Dodge 2500 4x4 5.9L CTD 3.55
07 Dodge 3500 4x4 SRW Mega 5.9L CTD 3.73
14 Ram 2500 4x4 Crew 6.4L Hemi 4.10
06 Chevy 1500 4x4 E-Cab 3.73 5.3L
All above are sold
Current: 07 Dodge 1500 5.7L Hemi 3.55 / 2010 Jayco 17z

Posted By: melackey73 on 01/29/07 12:31pm

You are just imagining a problems. Allison transmissions never have problems.

Posted By: eightballsidepocket on 01/29/07 12:57pm

melackey73 wrote:

You are just imagining a problems. Allison transmissions never have problems.

Our you Franklin under a new name[emoticon]

Regards, Eightballsidepocket

2005 Dodge Ram 2500 SLT 4x2 Quad Cab, Cummins, 48RE Tranny, Lg Bed, Line-X Spray-on Bed Liner.

06 T25BS Komfort Trailblazer TT

"If you can't say it in person, it isn't worth saying while hiding behind an anonymous P.C.!"

Posted By: Ray,IN on 01/29/07 10:20pm

The NSBU switch was known for malfunction in the early years. My truck required a new one, just as bluenote outlined. The early problem was corrosion from a poor weather seal boot. You can clean the contacts and wire terminals to see if it makes a difference, but the seal was re-designed in 2003 I think. You'll find the TSB by searching the forum. Run a search for posts by my screen name, and the subject should reveal. The dealer can read the trouble codes easily to determine this too.

The Constitution is not neutral. It was designed to take the government off the backs of people. Supreme Court Justice Douglas

Posted By: kudos383 on 01/29/07 11:16pm

Your gonna think I am crazy but i had an 2004 reg cab 4x4 2500 d/a that was doing the same thing,they finally fix it bye putting a reverse light indicator. switch and it was better

Posted By: sirwilliam on 01/30/07 04:58am

My NSBU switch (dark grey in colour) went out in 2004 on my '02 Silverado. The following were the symptoms:

1 = When selected to neutral, 4-LO would not engage at all, would flash and then return to 2-HI;

2 = When selected to park, electric door locks would not unlock conversely when selected to drive door locks would not lock;

3 = 1,2,3,D & R would not engage transmission, each selection would only flash then return to neutral.

NSBU switch was replaced with newer modified version (light brown) under warranty. Fix took about 40 mins. No problems since after driving approx 35,000 miles. Good luck.............

2012 Greystone Metallic, Chevy K3500HD LTZ, 11600 GVWR, 24500 GCVWR, X-cab, LB, LML Duramax 6.6ltr/M-74 Allison 1000, 3:73 Eaton G-80 "Locker" 11.5" Differential, 2009 Citation Classic 26RLS5W......

Posted By: catalinacon on 06/22/07 06:22pm

I have had same reverse problem as you. I was curios to know if you figured problem out?Please reply at your earliest convienence.Thank you!

Posted By: ib516 on 06/22/07 07:08pm

Only Allison problem I have heard of (well, besides this one [emoticon]) is a buddy at work had all of the tq converter bolts losen up on him (stock truck - less than 20,000 miles), and he found a puddle of ATF under the truck on his driveway and the whole undercarriage of the truck coated in ATF. I've never heard of that before or since. Truck is an 05 2500HD 4x4 which he bought new.

Posted By: Patster on 06/23/07 09:36am

I must have missed this one the first time around. I have seen this on other Allison equipped vehicles. It can actually be the brake light switch, if the TCM does not see a brake application it will not allow the shift into reverse, with some vehicles it also applies to any shift from park or neutral. GM trucks use a switch that has two sets of contacts, one for the lights and the other for cruise and transmission. If it is intermittent it may work okay for the dealer when they try it so it leads them down a different path. Just recently changed the switch on my father's 2006 Topkick which uses the same switch as the pick up trucks. His was not always making contact for the brake light circuit.
Just a thought.

Posted By: CTD2003 on 06/23/07 11:45am

Have to hate the dealer [emoticon] when they don’t have "trained personnel" [emoticon] and go into change parts mode till it works!! [emoticon]

Posted By: minnow on 06/23/07 03:40pm

And I hate when posters come here for answers and never bother to reply and let the rest of us know what the fix was.

Posted By: ttzcomet on 06/24/07 11:36pm

When this happens have you pushed your Onstar and asked them to do a diagnostic?

Posted By: LimogesMan on 01/30/07 05:40am

melackey73 wrote:

You are just imagining a problems. Allison transmissions never have problems.

That's what I thought! They are built as strong as the TorqShift. [emoticon]

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