Ecodiesel hot transmission temp

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sfairfield

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Bolton ONT
Ram Year
2018
Engine
ecodiesel
Hello folks,
I have owned my 2018 RAM 1500 ECO diesel since May 2018; has 75,000 KMs (50K miles +/-); all service done at dealer; no issues, EGR fix done last year; not a work truck; on a recent drive thru upper NY state & into PA, thru the rolling mtns, the trans temp jumped to 130C (265F); the trans temp lite came on, but neither the engine nor oil lite did - both remained normal at 100C; outside temp was a warm day at approx 80F; not towing; after slowing down, the temp did drop & when I pulled over, the fan was running full tilt; it did cool down & I completed the run to PA w/o issue. This only happened on the way to Lancaster, & all temps were normal on the drive back (to Toronto); note: the outside temp dropped to 60F on the return drive.
My dealer scoped upon my return, & as there was no fault indicated as the engine light didn't trigger & they couldn't find anything wrong. I am perplexed; kindly, they offered to cover the diagnostic charge, & offered a full tranny service (for about $1000) - but could not cover under any warranty (still under FCA) as the engine fault did not register.
OK - so I am now perplexed; & plan another long drive, which has me worried;
I have been reading various info on the Thermal Bypass Valve, which is supposed to control the coolant into the transmission cooler.
I am confirming with the dealer if they even checked this out, or the temp sensor?
Looking for any ideas?
thx
 

Burla

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Thermal Bypass Valve is in 6 speed, is that what you have? If so yes delete that junk. I'm not up on the 8 speed temp delete if that is what you have.
 

crash68

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It's not the the three-way valve that directs the flow of the coolant between the cab heater core and the transmission TMU.
If the transmission temperature is spiking, you more than likely need to replace the TMU. That's on the side of the transmission which has engine coolant to both heat and cool the transmission fluid, it also has the thermal control valve in it that directs the fluid to the cooler which is the top couple of rows on the AC condenser. The thermal control valve is part of the TMU and is not individually replaceable.
 

CanuckRam1313

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He is indeed! I just put one in my 19' 8spd and it is incredible in how it immediately brings the temps down on average 30deg/cel.

I also did a full trans service at the same time, and the shifting is so smooth and tight now, especially without the trans getting to insanely high temps.
 
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