So I was driving along I40 east today from Havasu City to Flagstaff pulling my bumper pull trailer weighing in about 14k lbs, and had this strange issue. Had the cruse set about 73 or so, started climing the hills and the tranny began hunting for gears like it does as well all know about 63 mph or so, but here is where it got weird. It downshifted, upshifted, downshifted again then upshifted again, finally I slowed to about 55 or so it stayed in drive, went down the other side of the hill and it shifted back into OD and all was well. Next hill climb was a quite a long steep grade as I began to slow it began to hunt again, down and up, down and up prob 3 maybe 4 times before it finally stayed in drive, as slowed more prob about 45ish it wanted to shift down again, and began to hunt, down and up, down and up prob 3-4 times again, then it just went into some fail safe shut down, the motor stopped accelerating and began to just coast, but never shut down completely, still idoled as I was on the shoulder. All the gauges were fine, Temp around 210, Oil pressure 60-70psi, tranny temp just slighty above 160 so I'm at a loss as to what happened? I coasted off to the shoulder, got out to check for leaks, nothing. Sat for a min or two with it running and then pulled back out and finished the climb. The rest of the ride into Flagstaff was fine, no problems. Anyone have this issue? Thoughts? Ideas? I've got 37k miles on it and had the recomemened Allison tranny service done about 3k ago before I left the east coast.

If possible, next time pull off side of road and shut your truck off. Wait a few minutes and restart. This resets everything. Last year I had to lockup the brakes while pulling my 18K 5'er. The tranny locked itself into 5th gear and would not downshift. First and only time I ever show the tranny temp gauge move. I pulled off side of the road and worked the shifter from park to first. My Edge programmer still showed I was either in 5th gear or park, nothing else. I shut off engine and waited a few, restarted and everything was fine. Perhaps one of the sensors in your Allison reacted and set off a chain reaction. These trucks have so many sensors it won't let you hurt anything. Maybe one sensor misfired. Good Luck John

Most of these electronic transmissions are loaded with sensors. While I am not an expert on the Ally... I would call an allison shop, describe the issue, and ask specifically... if not told... about the tranny sensors. You do not want this to happen again as it causes extreme wear on the transmissions components.