2003 Tahoe Z71 4L60E External Transmission Cooler Relocation

Discussion in 'GM Powertrain' started by BillM, Aug 25, 2011.

  1. BillM

    BillM Rockstar 100 Posts

    It appears that my 2003 Tahoe Z71's 4L60E Transmission needs more cooling than the current setup provides. It has an external cooler, as well as, the route through the radiator. It appears that the supercharger's air-to-water intercooler, which sits in front of the transmission cooler, blocks enough air that the transmission fluid is getting too hot? How hot is unknown-Don't have a temp gauge on the trans fluid.
    I have changed to Dextron VI is that enough?
    I would like to relocate the external cooler from behind the intercooler. Is that possible? To where? It needs air flow. It needs protection from road and rocks.
    Is the quick disconnect on the transmission and radiator a pipe thread fitting that can be changed to stainless braid aircraft fittings and hoses? Just to cut off mis-information, I have the quick disconnect tool required to disconnect the line from the transmission fitting. I mean the disconnect fitting that threads into the trans.
    Any help would be appreciated. Thanks.
  2. BillM

    BillM Rockstar 100 Posts

    No one seems to have any ideas out there??
  3. dpeter

    dpeter Epic Member 5+ Years 500 Posts

    Appears to be getting to hot? Temperature not known. So what brings you to the conclusion that it needs more cooling capacity?
  4. silveradotrailblazer

    silveradotrailblazer Epic Member 5+ Years ROTM Winner 5000 Posts

    Hello Bill. Its a holiday weekend so I'm sure alot of people we off the site till the weekend is over. I'm sure someone here can help you.
  5. Sierraowner5.3

    Sierraowner5.3 Epic Member 5+ Years 1000 Posts

    might be easier to plumb in another cooler then move the stock one.

  6. Boonduff

    Boonduff Rockstar 4 Years 100 Posts

    A wise old transmission rebuilder told me to bypass the so-called cooler in the radiator. Its main function is to use the heated coolant to bring the tranny fluid up to operating temp in cooler climates. In warmer climates or under heavy use your engine runs at 210 degrees if not more which is higher then the recommended temps for tranny fluid. I realize that the cooler is on the cool side of the radiator but why would you want the added heat from the coolant transfering to the tranny fluid. He also recommended I run a temp gauge and put in a Flexalite trans cooler with a small cooling fan attached. I mounted it in the return line up under the body. I also change fluid every 6 months with a high quality filter and fluid. He obviously knows his sheet because my 4l60e just rolled over 180,000 miles with lots of towing my 28' toyhauler in the Arizona heat.

    99'HEARTBEAT MODERATOR Staff Member 5+ Years ROTM Winner 1000 Posts Platinum Contributor

    With the.....Flexalite trans cooler.....What Are Your Transmission Temps Running at??
  8. 2COR517

    2COR517 Epic Member 5+ Years 1000 Posts

    I'm guessing you're getting some hard shifting which makes you think the trans is too hot. As mentioned, without a gauge you're playing darts in the dark diagnosing things.

    I would just move the trans cooler in front of the intercooler to give it better airflow. A better way to plumb your cooler is to run the hot line from the trans to the ext cooler, ext cooler to the radiator cooler, then back to the trans. This allows the ext cooler to draw off most of the heat, and the path through the radiator will prevent over cooling. As mentioned, the rad cooler is just as important to warm the transmission fluid for better economy.

    The fittings on the transmission should be normal 3/8 inverted flare fittings aka "brake lines" at your local parts store. If the lines are solid from the trans to the front, no need to replace them. Just splice in as necessary. Compression fittings are acceptable, this is low pressure.
  9. Boonduff

    Boonduff Rockstar 4 Years 100 Posts

    The Transmission runs right around 150-160 degrees on the hottest days [115 degrees] and runs about 175-180 degrees pulling my toyhauler up the 6 percent grades to northern Arizona. To clarify the fluid runs from the tranny to the factory aux cooler to the flexalite cooler and then back to the tranny.
  10. BillM

    BillM Rockstar 100 Posts

    Thanks for the replies. The most logical move is to get the temp gauge to see for sure. What is causing my concern is that the intercooler is sitting in front of the trans cooler, and the air gap is 1/16 of an inch. Not much of an air gap. There should be at least 3/8 to 1/2 inch air gap. I have already cut away a lot of the grill to get the intercooler mounted. Any more and I will have to get rid of the grill altogether. The 3/8 to 1/2 inch air gap is the normal gap between radiators for effective cooling. Taking into consideration the higher stall speed converter, which generates more transmission heat, and the over heated transmission fluid and fried transmissions by others in my area with the same kind of blowers installed, gives me nightmares. I will start with the trans temp gauge first.
    I have a Mag-Hyteh tranny pan with higher capacity, and am planning to change to Dextron VI. So maybe I am all right.

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