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Discussion Starter #1
I'm posting this here because it is tune related.

One thing that really bothers me with my truck is how freaking slow the transmission warms up, especially in the winter. It can literally take 45 min to 1 hour to get near full operating temp of 195F. I don't often drive more than about 30 minutes at any given time and a lot of the time it is far less than that. Bringing my son to school might be 15 min round trip.

Poking through the stock tune in HPTuners, I found this setting called "Cold Shift Exit." There is not much information about what it is and no related settings in HPT to clue me in.

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I know I have had other vehicles that would prevent torque converter lockup until a certain transmission temperature was hit and I was hoping this is what Cold Shift mode was for. I tried an experiment where I ran the same roads from a cold start, trying to maintain the exact speed limits. Outside air temperature was within about 3 degrees both days.

Here is the completely stock tune with Cold Start exit set for 105F:

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You can see it takes about 7 minutes to reach 105F and right then the torque converter locks up. And just FYI, TC lockup occurs at a maximum of 50mph in 5th and 6th gears. It takes almost 20 minutes for the transmission to hit 150F.

Here is the same tune, only with the Cold Start exit set to 150F:

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You can see 105F is achieve right about at the 7 min mark again, but the TC does not lock up. Instead, the TC stays unlocked until the 150F mark. This time, however, the 150F mark occurs just after 9 mins.

Here is a side by side of the two trans temp curves:

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These are both offset to when the ECM detects movement as I leave the driveway. I left the driveway when the trans temp was 46F both times and you can see they climb almost in lock step until the 105F tune hits 105F and locks the TC.

I suspect some of my aftermarket tunes may trigger Cold Start exit at an even lower temperature than stock because I feel like the TC locks up within about 3 mins of leaving my house on some of them.

One thing to mention is that the TC does not lock up at the exact instant that you hit 105 or 150F. There is a slight lag and it seems to be associate with the Trans Temp readout on the gauge cluster. If you ever log your trans temp you will notice it is almost always slight hotter than the gauge cluster reading. The cluster seems to be some kind of rolling average and so it lags the actual reading by about 10 seconds. TC lockup seems to correspond to the value in the gauge cluster, not the instantaneous temperature.
 

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Awesome post!

Wish I could log tranny temps

Sent from my SM-N950U using Tapatalk
 

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Excellent observation. I’ve always been curious about the trans warming. I do know 5* has the torque converter lock up at around ~84F rather than 105F. I always wondered why.
 

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That goes a long way to reasoning why the winter mileage takes a bigger hit than normal. That's a prime reason I use in WI. I can watch the mileage increase when trany temp rises past 170 degrees and it takes almost 20 mile of driving. KM
 

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Excellent observation. I’ve always been curious about the trans warming. I do know 5* has the torque converter lock up at around ~84F rather than 105F. I always wondered why.
I have no idea why they lower it other than most of the tuners seem to be in the south where this probably isn't as big of a deal.

The other thing is the torque converters, at least in my 2014, seems to be fairly tight. It's not like the RPM's are wildy shooting around when the TC is unlocked so driveability isn't poor.

That goes a long way to reasoning why the winter mileage takes a bigger hit than normal. That's a prime reason I use in WI. I can watch the mileage increase when trany temp rises past 170 degrees and it takes almost 20 mile of driving. KM
I was wondering about the MPG's as well. I don't know if the inefficiency of having the TC unlocked would offset the quicker warm up. That faster heating of the transmission is essentially coming from extra gasoline being burnt and putting work into the transmission fluid.

If you are driving 10 minutes, maybe its not helpful because the transmission is just barely getting up to temp by the time you get there. If you are driving 30 minutes, maybe it is helpful because the transmission is hotter a larger portion of the trip than it would be with the TC locked. I am sure there is a tradeoff somewhere.

My concern was less about the MPG's and more about getting the fluid hot to burn off condensation and whatever else might be in there. I can't imagine its all that good if the truck goes for literally weeks without ever getting over 140F.
 

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Different truck and trans but I’ve put >125k on a trans w/o it ever getting above 150. This was in South Texas tho so it was never really cold either...

Good info tho, I never even realize when mine is hot enough to lock...
 
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