Allison Transmission upshift problem

DanK wrote:
I am having a shifting issue with the Allison Transmission and I thought I would post it here to see if anyone had any insight on what it could be. The coach is a 2003 Newmar Kountry Star with the ISB 300HP motor and the Transmission is the 3000 series. The issue is that when I'm towing a vehicle behind the coach and I'm climbing a steep grade the coach downs shifts properly, but will not upshift properly. Example would be driving half way up a hill and the RPM will go to about 2400 after down shifting and would normally start to upshift at at around that RPM, but it goes in between gears. So the transmission tries to upshift, but doesn't actually upshift (I hope that makes sense). I have taken to coach into our Allison dealer and they could not simulate the issue, so they did not know what the issue is. The issue only happens when towing and only on very long grades. The other thing to mention is that when it tries to upshift is tries to do it every 1-2 seconds until I back off the on the gas pedal and then it will upshift. The problem is also starting to occur more frequently. I have owned the coach since new and it only started about 1000 miles ago. Coach have 67K milage if that is a factor. I would appreciate any insight you may have.

DanK wrote:
I am having a shifting issue with the Allison Transmission and I thought I would post it here to see if anyone had any insight on what it could be. The coach is a 2003 Newmar Kountry Star with the ISB 300HP motor and the Transmission is the 3000 series. The issue is that when I'm towing a vehicle behind the coach and I'm climbing a steep grade the coach downs shifts properly, but will not upshift properly. Example would be driving half way up a hill and the RPM will go to about 2400 after down shifting and would normally start to upshift at at around that RPM, but it goes in between gears. So the transmission tries to upshift, but doesn't actually upshift (I hope that makes sense). I have taken to coach into our Allison dealer and they could not simulate the issue, so they did not know what the issue is. The issue only happens when towing and only on very long grades. The other thing to mention is that when it tries to upshift is tries to do it every 1-2 seconds until I back off the on the gas pedal and then it will upshift. The problem is also starting to occur more frequently. I have owned the coach since new and it only started about 1000 miles ago. Coach have 67K milage if that is a factor. I would appreciate any insight you may have.

rgatijnet1 wrote:
The only way your Allison transmission would up shift is if the grade changed or if you were trying to accelerate and then let off of the throttle because you were happy with the speed. In that case, it would revert to the best gear to maintain that speed with the load. It would not up shift in to a higher gear if it could not maintain that speed because of the load and incline.

I have owned the coach since new and it only started about 1000 miles ago. Coach have 67K milage if that is a factor.

DanK wrote:
Thanks all for your input. I'll try to answer all your questions in hopes to find out what is going on.

1. Yes I have followed the recommender service intervals and have changed out the fluid to Transynd as well as both filters. I also checked the fluid and it is correct.

2. I would agree that the transmission should stay in the lower gear until I reach the top of the grade, but what happens is it tries to upshift but doesn't actually upshift. So it goes into that range between normal shifts, but doesn't actually shift up or down. When it get's in that range it tries to shift every 1-2 seconds, so it jerky (my technical term) while it's in the mode.

3. Pedel is completely compressed when it happens, but also will do it if not completely depressed.

4. Correct that the Allison service center was not able to diagnose, but they were also trying to simulate it and because they could not get the conditions right, were not able to track down the issue. The one thing they said was that they thought it was because the engine was not powerful enough, but the power has not changed since I purchased the MH and again this is a new problem that came up about 1000 miles ago.

DanK wrote:
It's doesn't feel like an injector misfire because it feels like the trans is going through the motions of trying to shift, but wont. Your theory of the engine governor telling the trans to shift, but the trans is saying no because it still feels the load is logical to me, and would fit what I'm feeling.

wolfe10 wrote:
Assume you have checked the Allison for diagnostic codes with the shift pad. Any codes?