Allison Shift Selector Goes Blank while driving

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Dave in Ohio

Member
Joined
Sep 2, 2008
Posts
23
Location
Columbus, Ohio
Both Friday and Saturday the same thing happened. After driving about 60 mph for a bit less than an hour, I noticed that the Allison shift controller was blank. (Normally it would show "6 6" with the word "MODE" under the right "6". Friday I drove about an hour more to a repair shop, and as I was pulling in I noticed that the display was again working normally. Saturday I drove about 20 minutes more to a truck stop and again the display started working normally as I pulled in. In both cases, I then turned the engine on and off a couple of times, shifted into all the gears a couple of times, cycled mode a couple of times, and, upon seeing consistent proper operation, continued driving for 5 or 6 hours with no problems.

My rig is a 2015 Newmar Ventana on a Freightliner XC Raised Rail chassis with Cummins ISB6.7 engine and Allison 3000MH transmission. Weather was clear with temps in the 30s.

While driving on the first day, I talked with Freightliner customer service. They warned me not to stop the engine until I was sure it was in Neutral as it won't start again if still in gear. They also suggested two 10 amp fuses as the likely culprit.

Today I looked for the fuses. As seen in the attached pictures, there are two spaces marked "XMSN SHIFT (OPT) 10A", both of which are empty.

Any ideas on where to start tracking this down would be much appreciated! Thanks!
 

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Utclmjmpr

Well-known member
Joined
Sep 14, 2009
Posts
5,619
Location
Cedar City, UT
I would (and have) lift the top plate and look for a loose or disconnected wire including at all the switch connections,,can't hurt.>>>Dan  ( I even had to replace a burned switch)
 

HueyPilotVN

Well-known member
Joined
Jun 5, 2012
Posts
2,591
Location
Lake Havasu City, AZ
I replaced the controller when it left me disabled on the side of the road.  Had it towed back to the campground.

After buying a new controller and not fixing the problem we found the problem to be a loose power wire that came from the area of the batteries.

I think that you might have an intermitant loose power wire.

Check that before buying a new controller.  I think that I ended up giving the replacement controller for a MH3000 to someone. 

Found the post.

http://www.rvforum.net/SMF_forum/index.php/topic,92914.msg839103.html#msg839103
 

Gary RV_Wizard

Site Team
Joined
Feb 2, 2005
Posts
76,141
Location
West Palm Beach, FL
Very likely a loose wire, either at the shifter pad or one of the relays at the TCU (transmission controller). Some wires may cause a loss of display power, while others may cause the tranny to drop out of overdrive as well, or even go into "limp mode". If it loses power while parked, the engine ignition won't be able to verify the tranny is in Neutral and so won't crank the engine.

Diagnosing this sort of thing is hit or miss, largely just wiggling wires and tapping relays or controllers to see if the problem can be reproduced. If nothing shows, you can start replacing components by guesswork, but some of them are pricey and it's strictly a gamble.
 
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