2010 Silverado Leaking Transmisson Coolant Lines

Discussion in 'Chevy Silverado Forum (GMC Sierra)' started by Backroads, Mar 29, 2013.

  1. Backroads

    Backroads New Member

    2010 Silverado 4.8 engine for the last few days I have noticed a "wet spot" about the size of a baseball under the front of the truck right behind the bumper. I first thought maybe I had splashed through a puddle or something but on the 2nd or 3rd time I raised the hood and the oil cooler lines for the transmission were wet and had a drip or two of fluid on them. The truck only has 73,000 miles and this seems a little premature to have these lines filing has anyone else had this issue?:shocked:
  2. j cat

    j cat Active Member

    I would locate exactly where its leaking. could be coolant not dexronVI.
  3. RayVoy

    RayVoy Active Member

    White cloth, or paper, might help. The tranny fluid is red, the engine coolant is orange, or green.
  4. TRPLXL2

    TRPLXL2 New Member

    Unfortunately that is not uncommon, the lines on these vehicles are paper thin and rot out relatively quickly. If you drive in salt that is killer for them.
  5. nickgiacalone

    nickgiacalone New Member

    I don't want to be the bearer of bad news but, my 2009 that I just got rid of had a very slight leak right by the fitting going into the trans cooler. I live in Michigan so we have a ton of road salt. I noticed it at about 66,000 miles.
  6. SurrealOne

    SurrealOne Former Member

    I'm down south in a largely salt-free area ... with a NBS truck that has 152k miles on it. While I got more mileage out of mine than others (probably due to lack of salt/brine), I just replaced my lines from the cooler, too.
  7. nickgiacalone

    nickgiacalone New Member

    150k miles seems reasonable, but every NBS & NNBS truck that I know of with 65-80k miles has had trans cooler lines replaced. (Remember, I'm talking about people in MI). We have 14 GM pickups in out fleet at work (all 2002 or newer) and everyone of them has had the trans cooling lines replaced around 70k miles.

    GM needs to do something about this. I read somewhere people were having their local hydraulic shops make lines the replacement lines with the theory that the heavy duty rubber definitely can handle the pressure, plus it will not rot. As long as it doesnt rub I could see this being a pretty good idea.
  8. SurrealOne

    SurrealOne Former Member

    150k mi is reasonable. However, were I up north it'd have been a fraction of that, I'm sure...
  9. TRPLXL2

    TRPLXL2 New Member

    I started replaced all my hard lines with braided stainless, you can do it yourself and they're lifetime. I priced a set of PS lines at a local hydraulic line shop, they wanted several hundred dollars for two lines. Think not!! I don't even waste my time replacing the lines with factory hard lines, in my mind it's a temporary fix.

    I will say my mom's Aveo has in interesting design on it's transmission lines, they are teflon coated from the factory. Maybe GM is catching on, then again the car is made in Korea lol!!
  10. Backroads

    Backroads New Member

    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?
  11. j cat

    j cat Active Member

    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 .
  12. TRPLXL2

    TRPLXL2 New Member

    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.
  13. aloxdaddy99

    aloxdaddy99 New Member

    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.
  14. j cat

    j cat Active Member

    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.
  15. Backroads

    Backroads New Member

    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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