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Allison Transmission Won't go into Drive


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The coach wouldn't start after fueling (no starter clicks or noise, Arens key pad displayed "6-3") and it would not go into "NN" either.  Sat there a bit after cutting off the chassis batteries to potentially reboot any computer and still no recovery.  Typical Sunday afternoon, called Allison and the local Fort Myers Allison shops...no one taking calls.  Went on line and Googled "Allison Fault Codes" and came up with nothing useful except a YouTube video where the guy said to hold the mode button in for 10 seconds to clear any codes. Worked!  Key pad showed "NN", coach started right up and we cleared the pump we were blocking for 2 hours.  We drove the last 4 miles to our RV park, backed in and shut it down...didn't have the courage to turn it off at the gate or anywhere between Loves and our site.  Tried to start it the next day and it did start...HOWEVER it will not engage DRIVE.  Reverse engages but nothing forward.  I'm still waiting for an Allison mobile tech to show up, check for error codes, etc.  Any ideas of what's happening?  While going through the prep for the technician, thought I'd find the Allison "brain" but I couldn't find it in the FRB or in the driver's side console.  Where to look??  (Allison 2500MH tranny behind a Cummins ISB 340/360)

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The Allison transmission electronic control module is attached to the basement ceiling in the main basement compartment.  In most of the big diesel coaches it has a felt covered plywood cover over it and the leveling computer. 

There should be an Allison fuse inline on a wire direct from the battery bay.  

Sometimes the trans will not engage if the engine is idling too fast.

Good luck.

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Found the transmission control box in the rear most curb side compartment on wall above & to left of inverter.  That's one question off the list.  Fort Myers getting hammered by rain and don't want to check out the "idle speed" suggestion until we get some clearing in case I need to go outside.  The coach did go into reverse so if the idle is too high I would think it would not go into reverse either.  Allison tech still not scheduled but they did get the billing info they wanted!

Not sure how this thread got into the "electrical" topic heading but had started the day with another entry about my 120v inverter circuit problem.  Guess that category carried over since I didn't have an option for selecting another pigeon hole.  Maybe one of the moderators can put this one in the "transmission" folder.

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I had this happen to me after a rest stop last summer. Looked online and was quickly reminded that the transmission will lockout "D" if the idle is too fast (pretty sure it displayed a code to that effect as well).  My mistake, was fast idling and forgot about it.

 

Edited by RoadTripper2084
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Generically...  An intermittent or sudden condition, unless one did something "out of the ordinary or NOT advised" usually comes from a connection issue or perhaps a "nicked" or chafed wire. There are THREE places, I think, that I would look....as well as the interconnecting wiring harnesses (Male and Female Plugs).  The ECM, the Tranny and the TCM. Moisture is a bad...as well as vibration.

I use the old trick of WD-40 (NASA created it for WATER DISPLACEMENT....the 40th formula worked). Spray the connectors or such....then you can use canned air or a MILD ELECTRONICS Cleaner....NOT A COMMERCIAL Electrical Cleaner.  The commercial MOTOR or Electrical Contact cleaners are too aggressive.  Even a shot of rubbing alcohol in a mist or vapor with a small spray bottle will work....then CANNED AIR.

That's my input....  Otherwise....it is gonna take some trouble shooting and possibly having the codes read from the Allison.

Allison tech support will walk you through the diagnostics from the key pad and help you identify the codes and their possible causes.  They are GREAT....

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The older allisons would default to reverse only if they couldn't read the output sensor, so not know if the transmission was slipping too much.  The plug was on the tail end of the transmission, maybe on the side? easy enough to find anyway, just remove, wiggle around as you put it back together and see if it shifts.  May have to remove the chassis battery ground connection for a minute to reset it.  I don't know if this applies to a 2010, but it's something you could look for online. 

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  • Solution

Allison Fort Myers was here yesterday, hooked up their diagnostic computer and checked for fault codes.  Nothing showed up, the coach started, the idle was perfect and tyranny went into drive and reverse without issue.  And no harness issues. The tech said there is an internal harness buried in the sump that may have been the cause and replacing it would take a day at their shop.  He considers the problem as an anomaly and recommended no immediate action be taken.  He will prepare a detailed diagnosis report with my bill for future reference should the problem reoccur.  He was pretty positive so will wait a bit to see if it happens again on the way home in late February/early March.  Hopefully!  I was impressed with the tech and would recommend Allison Fort Myers for any tyranny work in SW Florida.

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23 hours ago, lake49068 said:

Allison Fort Myers was here yesterday, hooked up their diagnostic computer and checked for fault codes.  Nothing showed up, the coach started, the idle was perfect and tyranny went into drive and reverse without issue.  And no harness issues. The tech said there is an internal harness buried in the sump that may have been the cause and replacing it would take a day at their shop.  He considers the problem as an anomaly and recommended no immediate action be taken.  He will prepare a detailed diagnosis report with my bill for future reference should the problem reoccur.  He was pretty positive so will wait a bit to see if it happens again on the way home in late February/early March.  Hopefully!  I was impressed with the tech and would recommend Allison Fort Myers for any tyranny work in SW Florida.

I'd get rid of that tyrannical tranny as soon as possible. 🤣

Seriously, good luck getting home, and hopefully it's not an internal tranny problem.

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Gave the problem/resolution some additional thought.  1200-1300 miles wandering home in March with a unit that has gremlins and the potential for breakdown, towing, finding a repair facility, parts and temporary lodging is not high on my wish list.  Visited Florida Allison yesterday, discussed the issue (internal wiring harness) and decided to spend the $, get some peace of mind and do it on my schedule locally (under 3 miles).  They can complete the work in a day so authorized getting the harness which they're guessing will take 7-10 days.  Still pretty impressed with the people at the shop and have confidence that they will get it right. 

 

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  • 2 weeks later...

Fort Myers Allison did the repair yesterday...new internal wiring harness and detent lever.  Even got a fresh load of Transynd and a new filter which takes care of the almost-due every 2 year maintenance.  They also found that the filter magnet was missing...will bring this up with my regular annual maintenance shop in October!  The coach was dropped off at 8am, picked up at 3:30pm and all is well.  Their shop is only 3 miles from our RV site which really took a lot of pressure off getting it fixed and they were very accommodating and easy to work with.  Worry gone and got a good night's sleep!  Oh, and got a bunch of Delta miles...

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Awesome that you got it taken care of Adam.  Peace of mind is certainly worth the expense, and you also got ahead of some other upcoming maintenance, which helps justify the cost.
Also glad to hear the positive experience with Fort Myers Allison.
It's good info for the Monaco community to know of trustworthy shops around the country.

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