Early Downshift

[pkmesser]

In a different thread, someone mentioned a problem with early downshifting with a 5 speed. This was while in CC. I seem to have the same issue, either in or out of CC. On a slight to very moderate grade, the tranny will downshift from OD to 4th, and then almost immediately to 3rd. I have used the approach, if I see a grade comeing, of dropping out of OD manually, in which case it does not then seem to want to downshift to 3rd nearly so soon. In that other thread, the person mentioned a possable "fix" via an upgrade to the ECM/TCM. I will be taking my MH in for the brake recall soon, and if there is a software fix for this problem, would like to get it done. I asked the shop where I will be taking it to check for a SB on this, but they haven't found anything yet.
Does anyone have any information on this?

[DriVer]

Quote:

Originally Posted by pkmesser Does anyone have any information on this?

pkmesser, The anomaly that you are concerned about only affected early model 2001 to 2003 motorhomes. Your 2005 or 04 chassis motorhome would have had the new programming change implemented.

If you are out or warranty, call Jon Brazel and discuss your situation with him. You will find that he does not bite and he will give you some options as to what you can do to improve your expectations in regard to the transmission downshift schedule.

[pkmesser]

Thanks, It's not a big issue, I had thought about it only because I'm taking it in anyway. Glad though that I already have the mod, if the earlier transmissions had a bigger problem!

[mfire1339]

Pk, I've determined it is just not very good programing on the allison. The trans seems to be protecting it self at the expense of the engine. It should pull a good load at peak torque in 4th gear and not down shift to 3rd.

Mike

[DriVer]

Quote:

Originally Posted by mfire1339 Pk, I've determined it is just not very good programing on the allison. The trans seems to be protecting it self at the expense of the engine. It should pull a good load at peak torque in 4th gear and not down shift to 3rd.

Mike, You do know that the process that you are talking about is actually initiated by the ECM. If there isn't sufficient RPM for the LOD the ECM will call for a shift PDQ.
.

[mfire1339]

Driver , ok the ECM is not programed to my liking. It needs a "idonwannadownshift" button.

Mike

[DriVer]

Quote:

Originally Posted by mfire1339 Driver , ok the ECM is not programed to my liking. It needs a "idonwannadownshift" button.

Mike, Call Jon Brazel to discuss those options.

[JonBrazel]

I guess anything is possible!

We can certainly set up the shift points thru the programming to hold each gear longer. This is accomplished thru the Allison TCM programming and is based off of % throttle position vs. mph & engine load.

[mfire1339]

Jon,

I'll see if I can come up with some "for instance" numbers as to what I want. Back not so long ago I could change some springs in valve body and gov. and get what I wanted. Different world.


Mike

[pkmesser]

I am like Mike, I need to observe a little more before we go to that trouble. But it's like it is waiting too long for the downshift from 5th to 4th, and then immediately jumping to 3rd. We will be out for a short trip to Calico in a few weeks, and then a long trip this summer, should give me plenty of whatifs to consider. Thanks everybody!