Re: Allison Transmission Questions Okay. Don't do it for more than about 30 seconds to prevent overheat. The Allison place should be able to tell you what the proper stall speed is. Low and High are normally 200 RPM or more. If it's high, you've got either C1 or C5 slipping in the trans. If stall is normal, my opinion is to start looking at sensor readings.