Re: Allison Transmission
What year and engine do you have? If you have a mechanical engine then it is very common. You should be able to get codes from the trans to tell you what the causes are. I had to replace mine and some of the symptoms where, D would flash and not go into gear, harsh up shifts and down shifts and once I even got a Do Not Shift Light. It could be a bad switch or another problem is that the pin on the linkage where the TPS conects breaks or is binding. Give me some more info and I will be glad to help. Good Luck