Allison 5sp: New Problem truck Down Gears from OD

[hopkins_fam]

I didn't know how else to title it but today, like 4-5 times, if i was going down a grade and completely let off the gas doing 55-60 the truck would down shift on its own to 4th (3500-4k rpm) and wouldn't shift back to OD til i slowed down low enough that the trans would downshift again then back up or shift to neutral and back to drive.

Ny input on what's going on here? The truck wasn't in Tow/Haul Mode it was in D driving normal through the mountains. I just think that's a pretty extreme downgear to goto redline of 4th.

 

[hopkins_fam]

Bump, headed out to Oh tomorrow for my 2 week hitch (350+ mile) and its kind of worrying me. Lots of mountains from here and KY

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[mike diesel]

Were you riding the brakes?

If so its called grade braking and its supposed to do it. Its designed to go to 4800 rpm with out damage. According to the owners manual anyways...

My truck will do it all the time if im coasting down a hill riding the brakes regardless if its in tow haul. Especially at the end of the 1/4 mile slowing down she shoots down a gear right to 4 grand.

 

[OnTheFritz]

^^^ it scared the crap out of me the first time also. I wonder how it sounds screaming out of the 5"! Lol

 

[hopkins_fam]

Very good to know, it had me quite worried. Do o need to relearn the trans or something for the 4-5 upshift? Seems like no matter where the throttle is it winter shift back to 5th unless i let it downgear again and then back up

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[duratothemax]

even in normal mode (non tow/haul), 5-4 grade braking is still active, though not as aggressive as when in tow/haul mode.

Its normal. If it downshifts and you want to accellerate again, just press the accelerator pedal (yes, I know you're "over the redline", but if you take a second to read the owners manual, you will see that it is not a problem) and grade-braking will be exited and the trans will shift back to 5th.

Ben

 

[hopkins_fam]

I understand the grade braking but when i get back on the throttle it winter upshift unless i go to neutral and back to D or slow down to diwnshift to 3rd then back up.

It won't upshift back to 5th with just throttle.

 

[Andrew]

I have a 6 spd idk if that makes a difference but mine would take forever to shift back up gears usually had to be back on the throttle for a little bit before it would shift back up

 

[chevyburnout1]

If the RPM is in the redline (3400+) then it should instantly upshift when you touch the throttle. If your below that rpm it may take a decent amount of throttle to hit fifth again. So your saying even after the hill on level ground it wont go back to fifth gear?

 

[hopkins_fam]

If the RPM is in the redline (3400+) then it should instantly upshift when you touch the throttle. If your below that rpm it may take a decent amount of throttle to hit fifth again. So your saying even after the hill on level ground it wont go back to fifth gear?

Correct no matter if i just touch the throttle or hold wide open it won't upshift unless i go down another gear then reaccelerate or goto neutral and back to drive

 

[duratothemax]

can you take a video of this and post it up for us to see? Might help diagnose it.

 

[hopkins_fam]

Ill try to get it to duplicate it, done it 3-4 times yesterday evening

 

[onebaddmaxxx]

reviving a thread….I searched and found this one….mine does this as well, and the more aggressive tune i have it on the more it will do it. its quite annoying hoping it could be disabled in trans tune

 

[hopkins_fam]

After a release mine started acting somewhat normal, its like it has a grade sensor but it will upshift now as long as i go past 1/4 peddle real fast. If i try and ease into the throttle it wont upshift to save its life.

Only over 1/4-1/3 peddle real fast. Its funny when im in OH my elevated idle works perfect and all the hills does great. Get home to VA and trans down gears like described and elevated idle will only kick on for a few seconds or so.