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68RFE flare during shifting

R.A.F

R.A.F

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New 2020 3500 dually with SO Cummins and 68RFE transmission. This week was the first time putting the truck to work towing a 16,000lb fifth wheel. Previous experience is with a 2014 3500 HO dually with Aisin.
Everything is good, until I hit an upgrade and the transition shifts from 6 to 5 and 5 to 4. The RPM flare is unreal, so much so I feel it will possibly affect the life expectancy of the transmission.

What do you guys think?
video attached.

I do wish the SO trucks were available with the Aisin transmission.
My old 2014 HO had 850 lb ft just like the 2020 SO.
 
First off I would try locking it outta 6th gear. I have built many 68’s for towing and after I have it I tell them to lock out 6th gear any time your going to be going up a grade make it stay in 5th gear. But if you are on flat land or no grades go ahead and let it go in 6th. Also we’re you trying to get on it while it was going up and it double down shifted.
 
No, it was not a double down shift, I was trying to I explain it did it from 6 to 5 as well as 5 to 4.
 
Okay. So it did two full down shifts. How high were the flares. I see them on stock trucks all the time but manageable with some aftermarket parts. To help keep it cool and higher pressure.
 
mostcorey95 said:
Okay. So it did two full down shifts. How high were the flares. I see them on stock trucks all the time but manageable with some aftermarket parts. To help keep it cool and higher pressure.
Click to expand...
I keep trying to post a video of the shift flare but its not showing up.

Basically, in 6th at 1500 rpm it will flare to 2500 rpm before settling at around 2000rpm in 5th.
 
What’s happening is the converter is unlocking than downshifting and relocking. I would say next time towing try tapping it down into 5th and see if it happens.
 
mostcorey95 said:
What’s happening is the converter is unlocking than downshifting and relocking. I would say next time towing try tapping it down into 5th and see if it happens.
Click to expand...
I'll look for that, I have an Edge monitor to keep an eye on the exhaust Temps etc. I can see when the torque converter locks and unlocks with that.
Next tow will be Sunday through the Smokey Mountains. It shouldn't take long to see whats happening, I'll also try pre-selecting 5th.

Thanks
 
Not knocking the 68RFE, but I have seen several hotshotter videos where they complain about shift flare with that trans. Hopefully, the preemptive downshifting suggested will minimize it for you.
 
trans tuning does away with the flares, if your into that kind of crazy stuff, like me.
 
Had a discussion with my regular service writer at my dealer today, he relayed the information to the techs. the flare it seems appears to be excessive and they want to check software versions. I have also been suffering a judder or surge when at cruise or light loads that I never encountered with my previous truck when towing.
Goes in on Friday.


Sent from my iPad using Tapatalk
 
R.A.F said:
Had a discussion with my regular service writer at my dealer today, he relayed the information to the techs. the flare it seems appears to be excessive and they want to check software versions. I have also been suffering a judder or surge when at cruise or light loads that I never encountered with my previous truck when towing.
Goes in on Friday.


Sent from my iPad using Tapatalk
Click to expand...
I'm jumping into and old thread, but did they resolve this with a software update?
 
No, software didn't change it. The flare appears to be the torque converter slipping before it locks up. Designed that way to protect the transmission.
Much preferred the Aisin in my old truck.

Sent from my SM-G998U using Tapatalk
 
elephantrider said:
trans tuning does away with the flares, if your into that kind of crazy stuff, like me.
Click to expand...

Yep weight reduction kit and trans tuning for me. No trans flare, it almost shifts to quick and locks up to fast kinda uncomfortable. But I have the tiniest, almost no flare at all, towing and heavy throttle.


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Lift89 said:
Yep weight reduction kit and trans tuning for me. No trans flare, it almost shifts to quick and locks up to fast kinda uncomfortable. But I have the tiniest, almost no flare at all, towing and heavy throttle.


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Click to expand...
What tuning are you using? I also have that same issue. Have since day one. Even after the software update it still does it. I just keep an eye on the trans temp and back out of it until it locks up then get back on it.
 
RJenkins1581 said:
What tuning are you using? I also have that same issue. Have since day one. Even after the software update it still does it. I just keep an eye on the trans temp and back out of it until it locks up then get back on it.
Click to expand...

OW tuning. He isn’t the best with trans tuning, but he’s not bad, I only have a 200rpm flare from 5th to 6th. Every other gear shifts really fast. His power tunes are pretty good. I’m sure there’s better tuners out there, but he got the job done first with a good price and good customer service. I have the thermal bypass, I haven’t seen temps get over 170, and I’ve had it for a year.


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