Cold weather 48re woes

[Amd241997]

I have a sub 300,000 mile ‘04 3500 5.9 HO with a stock 48re. I live in Utah and recently it’s been getting pretty cold here and thus starts my issues with the tranny. Typically my 48re OD locks up at around 50mph when driving normally, not going up a hill, or throttling it hard. But, whenever the truck is cold or tranny is below about 140 degrees, it won’t lock up. It’s really irritating and concerning since I typically have to get on the highway going 70mph+ after only a few miles of driving. I always let the truck warm up about 15 mins or to 100 degrees for the ECT before driving and then 180 degree ECT before driving hard. The issue I’m seeing is that my 48re won’t lock up until 50mph or at least 140 degrees trans temp. So I’m usually stuck going 65 mph on a 70 mph rated highway at about 2500 rpm sucking all my fuel and feeling like the transmission is gonna explode. Anyone have this issue or a remedy for it? I don’t have a lot of knowledge concerning the mechanical background of a diesel but any info would be great as it’s only going to get colder. Don’t know if a NV5600 would be the better choice because right now I’m really wishing it was a manual for this reason. Thanks guys!


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[Gearheadgregg]

My 48re in my 07 2500 did not last 300k Had to replace @ 150K , Try a filter change ?

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[03 unicorn]

I have a sub 300,000 mile ‘04 3500 5.9 HO with a stock 48re. I live in Utah and recently it’s been getting pretty cold here and thus starts my issues with the tranny. Typically my 48re OD locks up at around 50mph when driving normally, not going up a hill, or throttling it hard. But, whenever the truck is cold or tranny is below about 140 degrees, it won’t lock up. It’s really irritating and concerning since I typically have to get on the highway going 70mph+ after only a few miles of driving. I always let the truck warm up about 15 mins or to 100 degrees for the ECT before driving and then 180 degree ECT before driving hard. The issue I’m seeing is that my 48re won’t lock up until 50mph or at least 140 degrees trans temp. So I’m usually stuck going 65 mph on a 70 mph rated highway at about 2500 rpm sucking all my fuel and feeling like the transmission is gonna explode. Anyone have this issue or a remedy for it? I don’t have a lot of knowledge concerning the mechanical background of a diesel but any info would be great as it’s only going to get colder. Don’t know if a NV5600 would be the better choice because right now I’m really wishing it was a manual for this reason. Thanks guys!


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Me having an 03 with a nv5600 I cant help with part of your question but my other truck is a 97 Chevrolet 2500 with a 4L80 auto and it does the same thing. Until the trans is warm the converter won't lock. I think this is to help the engine warm up a little quicker.

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[InlineSix.7]

Me having an 03 with a nv5600 I cant help with part of your question but my other truck is a 97 Chevrolet 2500 with a 4L80 auto and it does the same thing. Until the trans is warm the converter won't lock. I think this is to help the engine warm up a little quicker.

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That certainly sounds logical. If this is what’s causing the converter to stay unlocked he could purchase an electric oil pan warmer. These are used in circle track racing to pre warm the engine oil before qualifying. They are adhesive and would warm up the transmission fluid just as well stuck to the bottom of the pan. One could run the cord right up next to your block heater and plug them both in at the same time. Glad I’m in NC. It was 70 degrees today


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[Amd241997]

That certainly sounds logical. If this is what’s causing the converter to stay unlocked he could purchase an electric oil pan warmer. These are used in circle track racing to pre warm the engine oil before qualifying. They are adhesive and would warm up the transmission fluid just as well stuck to the bottom of the pan. One could run the cord right up next to your block heater and plug them both in at the same time. Glad I’m in NC. It was 70 degrees today


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That’s actually not a bad idea looking into a warmer so thank you


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[Amd241997]

Me having an 03 with a nv5600 I cant help with part of your question but my other truck is a 97 Chevrolet 2500 with a 4L80 auto and it does the same thing. Until the trans is warm the converter won't lock. I think this is to help the engine warm up a little quicker.

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Stupid question but how does not allowing the trans to lock up help with engine warming? Cuz if that’s the case then I’m going to be looking into a grille cover which I really should be using anyways.


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[Amd241997]

That certainly sounds logical. If this is what’s causing the converter to stay unlocked he could purchase an electric oil pan warmer. These are used in circle track racing to pre warm the engine oil before qualifying. They are adhesive and would warm up the transmission fluid just as well stuck to the bottom of the pan. One could run the cord right up next to your block heater and plug them both in at the same time. Glad I’m in NC. It was 70 degrees today


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But I also work nights so having it plugged in while at work isn’t feasible


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[03 unicorn]

Stupid question but how does not allowing the trans to lock up help with engine warming? Cuz if that’s the case then I’m going to be looking into a grille cover which I really should be using anyways.


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Someone correct me if I'm wrong but with the converter in locked there is more friction and slippage in the trans building heat plus with it unlocked the engine is turning higher RPM creating more heat. At least that is how I take and understand it.

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[03 unicorn]

But I also work nights so having it plugged in while at work isn’t feasible


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I'm in the same boat as you 7pm-7am for me

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[Amd241997]

Someone correct me if I'm wrong but with the converter in locked there is more friction and slippage in the trans building heat plus with it unlocked the engine is turning higher RPM creating more heat. At least that is how I take and understand it.

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That would make sense it’s just sucky since I don’t like going above 2000rpm for extended periods of time due to more wear and tear and then of course higher fuel consumption. This morning was terrible though because I was on the highway for about 10 miles going 65+ at a little over 2500 and almost redlining. Didn’t like the sound or feel of it.


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