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intermittent retarder operation

April 06, 2016, 12:13:10 am

I have a problem with my retarder operating only part on the time.  It will sometimes work in the morning but fail in early afternoon.  I am not overheating the transmission as the temperature gauge does not get above 200 to 220.  I am using Allison specific synthetic transmission fluid changed about 10,000 miles ago.  Filters were changed also, and fluid is not low.  The joystick has been replaced.

When the retarder is not operative, the light on the retarder switch does not come on, nor do I hear the air valve venting at the rear.

Could this be a simple relay problem (the retarder relay at the right front of the dash) or could it be an air valve?

2000 U320 build #5633  73,000 miles

Thank you for any help or thoughts you may have.

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Re: intermittent retarder operation

Reply #1 – April 06, 2016, 07:49:14 am

DCF,

With your symptoms one other thing to look at is it could be your Allison retarder temp. probe starting to fail. When this probe just dies it will drop either one or 2 codes as they are designed to fail safe in the hot mode. If this happens the codes should be: 6223 and 6100. (sensor failed high and retarder temp high)  when this happens you will get a dash alarm.  At times if this sensor is starting to break down it will cause the retarder to start dropping out as you describe and the temp isn't high enough to get the 6100 alarm.

After daylight gets here  I  will post a picture of what you are looking for.  With you having a 2000 you most likely have a 4000 series transmission.  I don't have a 4000 book here with me but I think the sensor # is 295-11861 but you do need to make sure before you go and buy one.

Pamela & Mike

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Re: intermittent retarder operation

Reply #2 – April 06, 2016, 09:53:24 am

DCF,

Daylight has arrived and here are the pics.

Pamela & Mike

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