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  1. #11
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    Quote Originally Posted by Backroads View Post
    I pulled up a GM blog and it seems this happens quite often and 70k does not seem unusual what really rips me is the average GM repair cost seems to be $500 to $650 this is for transmission cooler lines I would hav expected this to be at least one half of that figure. Does anyone know the line pressure we are talking about? I believe I've seen older vehicles with 2 or 3 ply rubber lines and hose clamps on these joins. I f so is that possible here?
    there is no pressure. fluid pumps out of the transmission to the cooler then thru the cooler back into the transmission. disconnect a line [top] with the engine running and you will see its a slow flow.

    since its synthetic / transmission fluid the hoses must be for this application you cannot use just any hose. the hoses also must be able to take the heat which can be high from time to time.

    double clamping is recommended.

    only use a tubing cutter no saws. you could get some new metal tubing and bend into shape and connect with compression fittings.

    I would not spend more that $25 to fix this .

  2. #12
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    I tend to disagree with the line pressure statement, at idle in park yes very little pressure. But I just double checked the Helm's manual for the Silverado, 4l60e is 155+psi in any gear, and the 4l80e is 200+psi in any gear so yes while driving there is pressure.

    My boyfriend ran a transmission cooler with goodyear reinforced rubber hose, and double clamp method and he almost lost the transmission that way. He was at a stop light on a 90 degree day, and a guy next to him yelled and pointed under the truck. By the time he got in the parking lot, It had drained all the fluid out and there was nothing on the stick. Had to have it towed 75 miles back to the house to fix it, that's why we don't use rubber hose on anything crucial like that.

    Save $50 in materials to do it right, or replace a $1,500 transmission If this should happen to you.

    - - - Updated - - -

    I should also mention, now that we had our 4l60e rebuilt completely It has been retuned and a shift kit installed. Our observed line pressure now is 400psi, which is full apply pressure for the 4l60e, so for me It was a necessity.
    2004 Chevy Colorado
    LS1 5.7 swap/TBSS rear axle swap

  3. #13

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    The factory hose retension system SUCKS!! I was shocked to see what help the hoses onto the cooler when I installed the larger cooler on my truck. If/when I have a problem I will either retube and do my own SS tube with a short piece of braided hose or just run a complete braided line system. Either way it will have threaded fittings.





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  4. #14
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    thats internal pressure , not fluid pressure at the cooler lines. there is not much pressure because the line justs dumps the fluid into the pan with no restriction .

    internally before it exits the transmission you have pressure to operate the shifting.

    if you had as you say 200-400psi going thru the cooler the fluid entering the tranny sump would get air bubbles in it and your transmission would quickly get damaged.

  5. #15

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    Hey guys appreciate all the comments. I made an appointment with the local GM dealer to get the lines fixed, the appointment was for 4 or 5 days out the day of appointment I just could not bring myself to spend an estimated $500 on a transmission line repair. Got the line repaired, front brakes and rotors turned for $190. Thanks for all the help!!

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