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Minimum Trans Fluid Temp?

Discussion in 'The Garage' started by Hossbaby50, Jan 10, 2003.

  1. Hossbaby50

    Hossbaby50 3/4 ton status

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    Ok, I just got to Colorado 2 days ago. I run an external tranny cooler in sequence with the factory one in the rad. (fuild goes to external first then to the rad.) I also have a B&M gauge on the return line. In AZ my temp was around 140-180*. Now in Colorado it is 100-130* on the return. I am thinking that this is too low. Am I correct, or does the fluid heat up enough in the tranny to get to minumum operation temp.

    What is minimum op temp? I have heard 150-250* is this so?

    I am thinking that I am going to have to disconnect the external cooler to get the temp up. What do you all think?

    Thanks
    Harley
     
  2. chevyracing

    chevyracing 1/2 ton status

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    I thought with an auto cooler is better....
     
  3. Hossbaby50

    Hossbaby50 3/4 ton status

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    I thought so too, but I have heard people say that there is a minumim temp for proper fluid function too. I thought it was 150*
     
  4. HarryH3

    HarryH3 1 ton status Author

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    You want it to at least get hot enough to burn off any moisture from condensation in the tranny. Give Wendell a call at ShiftMasters in Golden. He builds some kicka$$ trannies and should be able to give you an answer. You can get his number at www.shiftmasters.com /forums/images/graemlins/thumb.gif
     
  5. ben427

    ben427 1/2 ton status

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    With the guage in the return line thats ot going to be an accurate decriptor of actual trans temp. Thats just the Temperature of the cooled oil. Before worrying about it i'd move the sending unit to the cooler feed line and see what the temp of the oil is that comes out of the transmission.
     
  6. Chris_T

    Chris_T 1/2 ton status

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    I have my guage in the pan and it reads about 140 - I've got a massive cooler on there too. I was concerned a bit at first, but was told 140 in the pan was OK. I have put cardboard up front a couple times to block the cooler in really cold weather and it definately makes a difference in trans temp.

    My dad has a 99 Sierra that he uses to tow with. He had an RV place install a coooler with a bypass in it so that when it is cool out (cool fluid) the fluid only goes through the stock cooler (which can actually warm it depending on coolant temp) until it warms up enough and then is sent to the tranny cooler. Was pricey, but it sounded interesting enough that I thought I might look into the parts required.
     
  7. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    A quality stacked plate cooler will do the same thing. If the ATF is too thick(read: cold) to get into the plates, it will bypass the cooler and continue using only the factory cooler until it's warm enough to need the extra cooling offered by the aux. cooler.
     
  8. Chris_T

    Chris_T 1/2 ton status

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    Cool. Ya learn something new every day. I take it the cooler has a bypass on it if the fluid can't be forced through the plates. Is it pressure related or is it a relative-flow kind of thing?
     
  9. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    I'm pretty sure it's based on fluid dynamics. If the fluid is too cold and thick to be forced into the cooling plates, the ATF takes the easy route through a bigger tube around the cooler. Once the ATF heats up and thins out, it is able to enter the plate system and get cooled.
     
  10. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    What I have been told and what I have read is you want to be under 200deg. 200 is the point where the seals start baking.
    As somebody else mention you do want to get some heat to remove condinsation. So ideal operating temp would be about 150-175 F.
    My temp sender is in the pan. My thought is that is where all the fluid is dumping after it has been heated by the clutches and workings. Next place I would think that would be a good place to get an operating temp is on the line out to the cooler. It would be easy to install a lsender in both lines and put a switch so you could flip back and forth and see temp out and how much temp the cooler is pulling out.
    Summer I usualy run about 160. Winter I'm sometimes lucky to get it to register on the gage. I a lot of times have to put a peice of cardbord in front of the cooler to get it up to 150F
    I run a Hayden Stack plate cooler and a Hayden gage on both trucks. The only time I have hit 200deg was pulling a LONG steep hill coming south on I75 from Knoxville TN. This hill was so long and so steep semis were down to 40 mph. I was towing a car so I was somewhere around 9,000 lb truck and car ( jetta on a dolly).
     

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