Attention: TDR Forum Junkies 
DonRam240
TDR MEMBER
2018 Ram 3500 pickup crew cab, long bed, DRW, Cummins with Aisin transmission.
My previous thread on this problem has disappeared, perhaps because it got too old/too long since last post. This is the follow up now that there has been a diagnosis and warranty repair done.
In brief, symptom: In 90 degree plus weather, carrying load of 11 foot slide-in camper at highway speeds up to 70 mph, after long drive and then a stop for something like lunch, 20-30 minute "heat soak" parked, on startup the trans would be stuck in 4th gear, one of the Limp Home modes. After several of these episodes, this was the one that clarified it most:
2+ hour trip, 90 degree weather with camper on truck, after fuel stop with about 20 minute heat soak, it was back in same 4th gear only limp home mode. Same nasty loud clunking when shifted into Drive. This time it did not clear with repeated restarts. Eventually had to stop in shade, open hood, and let things cool for a half hour before we could climb the last steep hill to get home. The trans temp started at 181 deg F, after shutdown rose to 185, then fell to 170 deg after a half hour. All other temps similarly normal. At that point, restarted and all was back to normal.
Drove with camper to dealer on another hot day and it was kind enough to misbehave on arrival, so they were able to pull trouble codes. The pertinent one turned out to be P0970. That directed them to a faulty circuit board that is integral to the Aisin trans valve body, so the valve body was replaced, clearing the code. Un-loaded test drive on a cooler day (day the repair done was later in month) was all normal. We won't have a valid test of the "cure" until next summer when we can duplicate the conditions of hot weather hauling camper at highway speeds, and stopping for a hot soak. At least the diagnosis makes sense, a circuit board that was not able to function in a normal higher part of the transmission's temperature range.
Many thanks to TransEngineer who provided several very helpful explanations and suggestions along the way to getting this fixed (we hope
Don
My previous thread on this problem has disappeared, perhaps because it got too old/too long since last post. This is the follow up now that there has been a diagnosis and warranty repair done.
In brief, symptom: In 90 degree plus weather, carrying load of 11 foot slide-in camper at highway speeds up to 70 mph, after long drive and then a stop for something like lunch, 20-30 minute "heat soak" parked, on startup the trans would be stuck in 4th gear, one of the Limp Home modes. After several of these episodes, this was the one that clarified it most:
2+ hour trip, 90 degree weather with camper on truck, after fuel stop with about 20 minute heat soak, it was back in same 4th gear only limp home mode. Same nasty loud clunking when shifted into Drive. This time it did not clear with repeated restarts. Eventually had to stop in shade, open hood, and let things cool for a half hour before we could climb the last steep hill to get home. The trans temp started at 181 deg F, after shutdown rose to 185, then fell to 170 deg after a half hour. All other temps similarly normal. At that point, restarted and all was back to normal.
Drove with camper to dealer on another hot day and it was kind enough to misbehave on arrival, so they were able to pull trouble codes. The pertinent one turned out to be P0970. That directed them to a faulty circuit board that is integral to the Aisin trans valve body, so the valve body was replaced, clearing the code. Un-loaded test drive on a cooler day (day the repair done was later in month) was all normal. We won't have a valid test of the "cure" until next summer when we can duplicate the conditions of hot weather hauling camper at highway speeds, and stopping for a hot soak. At least the diagnosis makes sense, a circuit board that was not able to function in a normal higher part of the transmission's temperature range.
Many thanks to TransEngineer who provided several very helpful explanations and suggestions along the way to getting this fixed (we hope
Don
