68RFE Shift flare question for trans guy

[Gonzo 1066]

I am very happy with my 2013, my 6th Dodge Cummins and the first automatic. There is a 50-100rpm shift flare with the 4-5 and 5-6 shifts. This sounds like a common trait with this transmission. Is this flare programed in?

 

[Bill Stockard]

Gonzo 1066,

Check post number 37 in this thread: https://www.turbodieselregister.com...m&p=2359239&highlight=shift+flare#post2359239

Bill

 

[Gonzo 1066]

Thanks Bill, My perception of the flare is not a slipping shift as much as a torque converter slip before lockup. I may be completly incorrect on this. My truck towes almost 100% of the time it is rolling.

 

[Bob V]

My 2011 does it but not all the time. I describe it as- TC unlock, pause, shift, pause, relock. Like I said it is not all the time, and I cant seem to find what parameters' cause it and how to prevent it

 

[transe]

Guys, you are exactly correct. Usually, a slight "flare" during a 4-5 or 5-6 upshift is the Torque Converter Clutch (TCC) unlocking (or actually, transitioning from full lockup to partial lock, where you have maybe 60-100 RPM of TCC slip). Yes, the sequence is: Unlock, shift, pause, and relock. The purpose of changing to partial lock is to reduce shift harshness.



I'm not familiar enough with the calibration details to tell you exactly when it will or won't unlock the TCC during these shifts. And it changes from model year to model year as they refine the calibrations, so there is no hard and fast rule. It also probably makes a difference whether you're in Tow/Haul mode or not.



Bottom line, I wouldn't worry about it. You could get a scan tool that displays TCC state (unlock, partial lock, or full lock) and watch what's happening, to verify that your "flare" is actually just a change in the TCC state.

 

[Gonzo 1066]

Thanks TE, This is the information I needed to stay in a good relationship with my new truck.