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Topic: Allison 3500 fault (Read 792 times) previous topic - next topic

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Allison 3500 fault
I've encountered a shifting problem the last couple days.  It's always at low speed in first gear making a sharp turn.  There's a hard shift and the Allison ends up in neutral with the selected gear window flashing.  I was finally in a position...

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Re: Allison 3500 fault
Reply #1
Brett,

Did the shift panel go to "snake eyes"?

There are two power leads to the Allison ECU.  The "memory" power which goes through a 5 amp fuse. 

The other one, and the power lead that is suspect is the one supplied by the ignition solenoid since...

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Re: Allison 3500 fault
Reply #2
Brett,

I hadn't noticed any other actions when the tranny died before, but today I did.  Everything was fine all day until I turned into our site for the night.  I remember what looked like a snowflake where the shift number should be.  All the...

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Re: Allison 3500 fault
Reply #3
When I had similar problems with my transmission it turned out the altenator was shot.

Start the generator to see if the problem goes away.

best, paul

Re: Allison 3500 fault
Reply #4
Brett,

In a word, YES.

But, easy to diagnose. 

With ignition off, identify the large lug on the ignition solenoid that does not have power.  Hook up a voltmeter to it. 

If symptoms appear, check voltage.  If no voltage, one of two issues-- either...

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Re: Allison 3500 fault
Reply #5
That surprises me.  I've never had a solenoid fail intermittently this way.  There is no way I can check voltages as you suggest unless I permanently install two volt meters.  The hiccups have never lasted more than two seconds, always at the end...

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Re: Allison 3500 fault
Reply #6
Last night the Cummins ECM threw a Speed Sensor Fault.  Could this be connected to the Allison problem?  Should I head for Cummins, Allison, or FT? 

Re: Allison 3500 fault
Reply #7
Brett, I had a speed sensor fault. It it gets bad enough the Allison will stop shifting. Mine was caused by a rear main seal leaking a little and it fell on the sensor. The sensor is easy to change out but the why is the hard part. I took my...

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Re: Allison 3500 fault
Reply #8
The coach stopped shifting when I was halfway into my site at Rainbow's End.  At least my power cord reached the pedestal.  Anne heard sparking around the tag axle.  It's dark and pouring rain now.  Tomorrow I'll crawl underneath.  From your...

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Re: Allison 3500 fault
Reply #9
Brett,

There are actually two speed sensors-- both external to the transmission and easy to access/replace/ etc.

But, before doing that, check that the connections from then are clean and tight-- they live in a dirty, wet environment.

Take some...

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Re: Allison 3500 fault
Reply #10
Given intermittant ECM/TCM problems and sparking noise, I would be looking for a power connection problem.   Bad/loose ground strap from engine / trans block to chassis, connections that get stretched/moved when the rear axle/tag shifts, etc.  ...

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Re: Allison 3500 fault
Reply #11
The "bad connection" suggestions sound plausible based on our experience. The Allison 3060 on our SOB went to "limp mode" with a speed sensor fault while we were driving on icy roads in blizzard conditions (dangerous operation as a result of some...

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Re: Allison 3500 fault
Reply #12
It was all my fault.  I had added a second positive battery cable this summer to try to improve starting performance.  I used flexible welding cable, and didn't tie it down enough.  In the heat of this fall's driving, on section sagged enough to...

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Re: Allison 3500 fault
Reply #13
:facepalm: D'oh! :facepalm: Thanks for confirming your humanity. We refer to those events as "self inflicted wounds." Fortunately, it was an inconvenience rather than a show stopper. Nice detective work! ^.^d

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  • John Haygarth
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Re: Allison 3500 fault
Reply #14
Brett we all make mistakes but at least this one got some brains going and we all shared in the "learning curve" of what may cause something like this to happen. So, it actually was a good thing in my opinion, now I know what may cause this to...

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  • Gary Bouland
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Re: Allison 3500 fault
Reply #15
Brett, Welcome to the club.  I have been fortunate that my mistakes at least have not killed me or anyone else. :)   And..... All of us here now know that a LIBERAL application of wire ties can save a lot of trouble.
Glad you found it.
Gary B

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Re: Allison 3500 fault
Reply #16
I'm having similar problems. Intermittently, as I'm slowing, the transmission will slam into 1st gear. Other times, I'll get the flashing gear indicator and the transmission shifts into neutral (once when turning right on a freeway onramp). When...

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Re: Allison 3500 fault
Reply #17
moodmeister,

Please tell us what coach or what transmission you have!!!

Certainly you will want to verify both 12 VDC feeds to the Allison ECU as well as ground are good and 12+ VDC when this occurs before proceeding.

When we know what coach you...

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Re: Allison 3500 fault
Reply #18
My error codes are:
d1 - 2214 (engine speed sensor)
d2 - 6933 (central operating processor timeout)
d3 - 3500 (power interruption)

Allison Transmission Codes Manual

Well, the good news: you...

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Re: Allison 3500 fault
Reply #19
Oops! Yes...of course, I did not post the pertinent information  :facepalm:

Coach: 2002 U 295, build number 5973
Engine: Cummins ISL-400 (rebuilt at great expense)
Transmission: Allison 3000 MH 6 speed with retarder and WTEC-III Controls SN 6510310525

Where...

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  • Last Edit: November 25, 2020, 09:48:36 pm by moodmeister