Aisin downshift ?

[CThomsen]

My 2013 has 28k miles now and when slowing down to stop the downshift into first is very harsh and seems to be getting worse. It feels like you are suddenly stomping on the brakes when it downshifts. Anyone else have this issue? Doesn't happen with every stop but definitely over half of the time. I was going to do my first transmission drain and fill soon but am now thinking of taking to dealer to let them check it out. Thanks

 

[rrl989]

There was a re-flash for the Aisin harsh down shift that was done on my 2014, but I don't know if it applied to the 2013 ?

 

[CThomsen]

Thanks. I'll. check with my dealer

 

[sag2]

Flash will fix it right up.

 

[gsbrockman]

Flash will fix it right up.

I read elsewhere that a reason for the harsh downshift was as follows :

"The low sprag (which too was failure prone) has been removed. The only issue with this is you will have a harsher 2-1 downshift. Please read on the forums that several users have complained of this exact issue. You cannot fix this, it is just a side effect of getting rid of the sprag, not a durability issue in the least."

Comments and / or ideas????

 

[transe]

I read elsewhere that a reason for the harsh downshift was as follows :

"The low sprag (which too was failure prone) has been removed. The only issue with this is you will have a harsher 2-1 downshift. Please read on the forums that several users have complained of this exact issue. You cannot fix this, it is just a side effect of getting rid of the sprag, not a durability issue in the least."

Comments and / or ideas????

Yes, for 2013 the Overrunning Clutch (ORC) was removed from the Aisin trans. The ORC and the B2 clutch both hold the rear annulus gear reaction torque in 1st gear, so in 2013 and beyond the ORC is gone and now the B2 clutch (alone) holds the reaction torque.

The ORC is (was) a mechanical one-way clutch that locks (holds torque) in one direction, but freewheels (holds no torque) in the other direction. In 1st gear, if the engine / drivetrain are spinning "clockwise," the reaction torque on the rear annulus gear makes it want to turn counterclockwise (but the ORC locks and won't let it). In 2nd gear, the rear annulus gear turns in the clockwise direction (so the ORC freewheels and lets it turn). This makes the ORC an ideal shift element for the 1-2 upshift, since we don't need to control it at all (we simply engage the applying clutch for 2nd gear, and the ORC releases when the rear annulus gear starts to turn in the clockwise direction). But, the ORC will not provide any engine braking. In 1st gear, driving forward, the ORC locks. But at closed throttle (where the drivetrain would be trying to drive the engine, instead of vice versa) the ORC unlocks, allowing the engine to fall back to idle speed (while the drivetrain pulls the rear annulus gear in the clockwise direction). So we need the B2 clutch to provide engine braking in "manual" 1st gear (ERS "1"). The B2 clutch holds the rear annulus gear from turning in either direction, so the trans stays "in ratio" even at closed throttle (like a manual transmission does, if you don't disengage the clutch).

So, the ORC provides a smooth 1-2 upshift, and also a smooth 2-1 downshift (since the engine can simply remain at idle speed, with no engine braking effect, assuming the B2 clutch is released). But for 2013+, the ORC is no longer there, so we must use the B2 clutch all the time in 1st gear. This means that, on ANY 2-1 downshift (not just a "manual" pulldown to ERS "1"), you will get engine braking. That in itself means the 2-1 downshift will be more noticeable. And doing the clutch-to-clutch handoff is more complicated (the timing of the B2 clutch apply must be just right, compared to when the releasing clutch loses torque capacity) than just allowing it to drop onto the ORC.

So yes, elimination of the ORC inherently makes it more difficult to maintain a smooth 2-1 coastdown shift.

 

[MattandLana]

Trans Engineer that's a fantastic description, many thanks for taking the time to set it out so clearly.

 

[CThomsen]

Finally got truck to dealer today. They did at least 4 updates. Harsh 2-1 downshift is gone. One also should fix the fuel filter monitor on the evic-it was giving me 7500-9000k mile change intervals.

 

[Deleted member 995608]

Yes, for 2013 the Overrunning Clutch (ORC) was removed from the Aisin trans. The ORC and the B2 clutch both hold the rear annulus gear reaction torque in 1st gear, so in 2013 and beyond the ORC is gone and now the B2 clutch (alone) holds the reaction torque.

The ORC is (was) a mechanical one-way clutch that locks (holds torque) in one direction, but freewheels (holds no torque) in the other direction. In 1st gear, if the engine / drivetrain are spinning "clockwise," the reaction torque on the rear annulus gear makes it want to turn counterclockwise (but the ORC locks and won't let it). In 2nd gear, the rear annulus gear turns in the clockwise direction (so the ORC freewheels and lets it turn). This makes the ORC an ideal shift element for the 1-2 upshift, since we don't need to control it at all (we simply engage the applying clutch for 2nd gear, and the ORC releases when the rear annulus gear starts to turn in the clockwise direction). But, the ORC will not provide any engine braking. In 1st gear, driving forward, the ORC locks. But at closed throttle (where the drivetrain would be trying to drive the engine, instead of vice versa) the ORC unlocks, allowing the engine to fall back to idle speed (while the drivetrain pulls the rear annulus gear in the clockwise direction). So we need the B2 clutch to provide engine braking in "manual" 1st gear (ERS "1"). The B2 clutch holds the rear annulus gear from turning in either direction, so the trans stays "in ratio" even at closed throttle (like a manual transmission does, if you don't disengage the clutch).

So, the ORC provides a smooth 1-2 upshift, and also a smooth 2-1 downshift (since the engine can simply remain at idle speed, with no engine braking effect, assuming the B2 clutch is released). But for 2013+, the ORC is no longer there, so we must use the B2 clutch all the time in 1st gear. This means that, on ANY 2-1 downshift (not just a "manual" pulldown to ERS "1"), you will get engine braking. That in itself means the 2-1 downshift will be more noticeable. And doing the clutch-to-clutch handoff is more complicated (the timing of the B2 clutch apply must be just right, compared to when the releasing clutch loses torque capacity) than just allowing it to drop onto the ORC.

So yes, elimination of the ORC inherently makes it more difficult to maintain a smooth 2-1 coastdown shift.

When my eyes uncross, I'll have to reread this again.

 

[DHuffman]

Yes, for 2013 the Overrunning Clutch (ORC) was removed from the Aisin trans. The ORC and the B2 clutch both hold the rear annulus gear reaction torque in 1st gear, so in 2013 and beyond the ORC is gone and now the B2 clutch (alone) holds the reaction torque.

The ORC is (was) a mechanical one-way clutch that locks (holds torque) in one direction, but freewheels (holds no torque) in the other direction. In 1st gear, if the engine / drivetrain are spinning "clockwise," the reaction torque on the rear annulus gear makes it want to turn counterclockwise (but the ORC locks and won't let it). In 2nd gear, the rear annulus gear turns in the clockwise direction (so the ORC freewheels and lets it turn). This makes the ORC an ideal shift element for the 1-2 upshift, since we don't need to control it at all (we simply engage the applying clutch for 2nd gear, and the ORC releases when the rear annulus gear starts to turn in the clockwise direction). But, the ORC will not provide any engine braking. In 1st gear, driving forward, the ORC locks. But at closed throttle (where the drivetrain would be trying to drive the engine, instead of vice versa) the ORC unlocks, allowing the engine to fall back to idle speed (while the drivetrain pulls the rear annulus gear in the clockwise direction). So we need the B2 clutch to provide engine braking in "manual" 1st gear (ERS "1"). The B2 clutch holds the rear annulus gear from turning in either direction, so the trans stays "in ratio" even at closed throttle (like a manual transmission does, if you don't disengage the clutch).

So, the ORC provides a smooth 1-2 upshift, and also a smooth 2-1 downshift (since the engine can simply remain at idle speed, with no engine braking effect, assuming the B2 clutch is released). But for 2013+, the ORC is no longer there, so we must use the B2 clutch all the time in 1st gear. This means that, on ANY 2-1 downshift (not just a "manual" pulldown to ERS "1"), you will get engine braking. That in itself means the 2-1 downshift will be more noticeable. And doing the clutch-to-clutch handoff is more complicated (the timing of the B2 clutch apply must be just right, compared to when the releasing clutch loses torque capacity) than just allowing it to drop onto the ORC.

So yes, elimination of the ORC inherently makes it more difficult to maintain a smooth 2-1 coastdown shift.

Thanks, great explanation.

 

[Mega]

Finally got truck to dealer today. They did at least 4 updates. Harsh 2-1 downshift is gone. One also should fix the fuel filter monitor on the evic-it was giving me 7500-9000k mile change intervals.

I'm new too this site.
I have 2013 Ram 3500 mega cab with As68rc transmission with the very same symptom. Is your transmission still performing or did symptom come back?