2004 Patriot Thunder, C-12, Tag Axel
When beginning a descent on an approx. 5% grade, I noticed that the Jake brake was not functioning. After pulling into a turnout to check the situation, I noticed that the push-button shift selector displayed "5". This seemed unusual since I would normally see "6" given that it was in the "D" (Drive) mode. When I pressed the "D" button, "5" remained on the display and there was no forward motion from the transmission. When the "N" button was selected, "N" was displayed. Next I selected the "R" button and "R" was displayed as expected and engaged the transmission. Next the "D" button was selected and the display changed to "6" as expected but there was still no forward motion by the transmission. After several attempts there was no forward motion regardless of the gear selected. However it would consistently engage the reverse gear. The “Check Transmission” light was never displayed during this time. All fluids and batteries were good. Temperatures were in the normal range.
After the coach was towed to a service facility two diagnostic codes were found: 2-5-1-1 “Output Speed Sensor” and 5-4-5-4 “Oncoming Ratio Test”. I was told that the 5-4-5-4 code was the most problematic of the 2 codes. A tech from an Allison Dealer was called in for further analysis. He concluded that the fault was low pressure in a section of the transmission that engaged gears 1 thru 4. He recommended that the transmission be removed for repair of the problem section of the transmission and that a rebuild would not be necessary. However when the service manager was contacted to schedule the repairs, the story changed. He said that the best solution would be to install a rebuilt transmission (around $9k).
We drove a little over 10k miles this past year and the coach performed flawlessly – no indication of any transmission issues until the above incident occurred. It seems that a rebuilt unit would not be required with only 64,000 miles of service.
Has anyone had an experience that could offer a perspective on this situation?