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Transmission Retarder – 2000 XL Liberty
Last year after a long road trip to Petosky MI and several mountain passes my retarder crapped out as I made it home. It worked flawlessly the entire trip and I was careful to keep temperatures within the normal range. I took it into Prevost this week and they informed me that they had undertaken a complete diagnostic test and determined there was no faults on the “Prevost” side of the system and concluded it was internal within the Allison transmission unit and furthermore Prevost would not work on this component.
I do do not know enough about the mechanism of the transmission retarder and feel at a bit of a loss of where to proceed. I just don’t want to be taken for a ride as opening up the transmission sounds like big bucks to me. But it is imperative that the retarder is fixed.
As an aside the shifting of the automatic transmission is flawless and shows no signs of unusual behaviour.
Your thoughts are greatly appreciated.
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5 Replies
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That’s an Allison Transmission responsibility. It could be as simple as a problem with the transmission control module or a temperature sensor, or something more serious.
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This is the written response from Prevost….
Hello Allan,
We have checked the wiring diagrams and checked all relays R24, 76, 82, EF1 and EF2. A wire test was performed from FJB to RJB and they were Ok. Another wire test was performed from FJB to H solenoid/N solenoid and wire was Ok.
Checked for fault codes and had code 45 open solenoid circuit H. Performed a test from ECU (T connector blue) pin T19/T23 to retarder lock pin A/B and retarder accumulator pin A/B and found the H solenoid out of value specs, normal value should be 3.26 and actual at 02.
Hope that info helps but if Allison wants to give us a call no problem. They can look for Eric or Dennis at our shop.
Have a good evening
I am am unsure what the H solenoid is? Is this solenoid an Allison part?
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Sure sounds like an internal part.
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That fault code is the result of either the wire from the TCM to the trans is open or the solenoid has gone open. If the wire ohms out ok the retarder solenoid is an external component of the side of the trans. The solenoid is a common failure item.
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I received my coach from Allison this morning. The internal solenoid and related pig tail wires were the culprits. Both were changed out and my pocket book is lighter yet again. $1169 US was the cost.
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