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Discussion Starter · #1 ·
Any input would be appreciated

Last winter the temperature dropped below zero and my truck would not shift into overdrive. The Ram left me with no choice but to face the hundred and sixty five mile drive without ever having overdrive while maintaining a low speed and low RPM. I had to leave the truck in storage and catch a flight before it ever warmed up outside, during the drive the temperature gauge never really climbed even into normal range. I'm suspecting the temperature in the transmission never warmed up enough to allow overdrive but from everything I can find the drive should have been long enough to warm up the truck however I never stopped it and turned it off and restarted the truck. could that have anything to do with it? I found a lot of information such as the information below but none that specifically cover that year of that truck.



NOTE: THIS BULLETIN APPLIES TO VEHICLES EQUIPPED WITH RWD
TRANSMISSIONS 42RE, 44RE, 46RE, AND 47RE.

Discussion:

In ambient temperatures of minus 5 degrees F and below, the Powertrain
Control Module (PCM) will electronically inhibit the transmission from
shifting into overdrive. This will protect the transmission from damage
if the automatic transmission fluid begins to freeze. This is a new
feature for the 1996 model year.

The PCM will allow overdrive operation once the ambient temperature has
risen approximately 7 degrees above the temperature the transmission
overdrive was inhibited at, or an ambient temperature of + 2 degrees F,
whichever occurs first.

NOTE: THE PCM USES A DIFFERENT TEMPERATURE SENSOR TO MONITOR THE
OVERDRIVE DISCONNECT THAN THE OVERHEAD CONSOLE. DO NOT ATTEMPT TO
MONITOR THE OVERDRIVE DISCONNECT WITH THE OVERHEAD CONSOLE.
 

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In such extremes, you're just gonna have to physically block the radiator to limit airflow over it. That's the quick and dirty method. Even some cardboard between the grille and radiator will work. Ifyou notice, even some 18-wheelers, in similar conditions, will have something like this. I've even seen some that are adjustable. A more advanced method is having an external cooler with a thermostat control. Essentially, the computer will lock out OD until the trans fluid gets up to around 60 degrees, so quickest way to affect that is to restrict airflow across the radiator.
 

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'95 2500 8.L 4x4, '03 1500 5.7L 4x4 OffRoad, '85 W350 5.9L, '02 1500 Sport 5.2L
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Yes, the engine management system prevents OD below or above certain temperatures. 170 seems to be the lower limit at least on my '95. Incidentally, the system also supposedly prevents closed loop fuel management below this general threshold. I had a 170F t-stat which I pulled for a 180. I left Montana years ago, but I head to Canada and the Rockies every year for work and travel. The 'stat only sets a minimum operating temperature in moderate temps. Here in the SWest it makes no cooling difference what the 'stat opening point is, if it's hot outside the thing is fully open once warmed up. The problem with the V-10 is that the engineers designed a cooling system that would gradually warm the engine to keep the cylinders round in operation, minimizing bore wear. The thermostat setup has a constant bypass of coolant that is not regulated by the 'stat. You'll notice in cool weather and long downhills you can drastically overcool the engine. Look back at online forum threads from years ago, a lot of people had poor heat in extremely cold weather. This was part of the reason. Before I thought of building a restriction for the bypass, I made some clear Lexan cards to restrict the airflow through the radiator. That is what I still use today. Good luck, Mike.
 
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