Hello, I'm new here but have often searched for bus issues and this site would pull up.
Here is my issue. I have a 2002 Thomas with Cummins 5.9 and Allison 2000. When down shifting the trans will violently shift from 2nd to 1st as if you stomp the brakes momentarily. Shifts through all other gears up and down perfectly. I did figure out today that I can manually shift into 2nd at about 20-25 MPH and it shifts fine. Changed the fluid and filter last week to no avail. It's not throwing any codes either.
We don't have any software for the Allison. A guy bought a code reader a few weeks ago from a parts store and the commercial sales guy said it will read the allison codes, but we've yet to be able to get any codes on any of our buses with it.
If you can find another district, or maybe a city/county shop near by that can run a trans health report, that should give you an idea of the clutch condition, and how much wear compensation the trans clutches have. I have had no-codes on this condition myself. Otherwise you may have to go to an Allison shop...Did the fluid change aggravate the condition?
At first the fluid change seemed to help, I was driving it to get up to temp and for the most part it was shifting fine. Checked the fluid and topped off to level and drove again and it was back to shifting hard. Route driver says it is inconsistent sometimes worse cold and sometimes worse warm. Guess we're just gonna have to take it in to our Allison shop. Thanks
Allison trans hard down shift
Posted - 02/22/2018 : 11:30:40 AM
