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  1. #1
    Sr. Engineer nickgiacalone's Avatar
    Join Date
    Mar 2009
    Metro Detroit, MI

    Default Transmission line leak

    I have been putting a little bit of money into my truck this week to get it back in ship shape. I needed a new TPMS Sensor, had that fixed, installed new lock actuators and today replaced inner and outer tie rods on both sides (only needed right side inner, but why not do them all while in there). So today after work I pulled her onto the hoist to do the tie rods. While looking over the truck from the bottom side I noticed one of the trans lines near the front of the truck just above the front skid plate had some moisture around it. It has a very, very slow leak (trans fluid has never been low). I'm not exactly sure where in the line it is leaking but that isn't a concern as I realize I will have to replace the line. My main question is, how difficult is this? This is the first vehicle I have ever owned (always been a lease guy), so I have never worried about anything other than oil changes. I am pretty mechanically inclined just wanted some opinions on the difficulty of this job, time requirements, tools needed, etc. Also, how many trans lines are in the front of the truck and would it be worth changing them all out at the same time once/if I dive into this project.

    By the way, the truck has 68,XXX miles and I live in the Metro Detroit area (the salt is GREAT for our vehicles).

    I'm not too concerned with having to put some money into it to keep it a nice vehicle, since it was new in Jan 09 the only money I have put into it other than what I've done this week is L.O.F.'s and tires.

    Anyone who can shed some light on this would be greatly appreciated!
    2013 Silverado 1500 4x4 LT, Z71 Appearance Package, Vortec 5.3L AFM
    Victory Red, Ebony Cloth
    Custom pin striping, Bed Rail Protectors, GM Bed Liner, Husky Liner Floor Liners, Tint, Wade In-Channel Window Visors, Tractor Supply Black Low Profile Toolbox

  2. #2


    These lines rusting appears to be a common problem, I haven't had any leak on the trucks I've owned; but my wife has had a couple on her cars. She drives very few miles a year, so I suspect that is the reason.

    Anyway, both times there was a leak under the plastic clip that holds the line(s) in place, remove the clip and it will leak faster.

    The biggest problem (for me) was getting new lines. I wanted lines that were fitted to the vehicle and GM didn't provide them. I did find a set, through a company that made custom hoses and lines, then wait for them to be made and shipped.
    Once I had the new lines, it was an easy job to replace, just a little (actually, a lot) messy. I had the front in the air (jack stands), but fluid still leaked all over.

    '09 Avalanche LTZ - Black
    '05 Envoy XL (sold)

  3. #3
    Sr. Engineer nickgiacalone's Avatar
    Join Date
    Mar 2009
    Metro Detroit, MI


    What kind of vehicle did you change them on, our mechanic at work told me that changing the lines in an 05 2500 D'max was very involved and difficult.

    I do about 25K a year, so not driving doesn't seem to be my issue.

    If this job can be tackled by someone that has never done it before I was thinking about getting the lines made at the local hydraulic shop that makes all the lines for out hydro controlled salters at work. Any thoughts on this and/or if it would even work? I couldn't see it costing much more then buying the OEM lines that will probably rust out again.

  4. #4
    TRPLXL2's Avatar
    Join Date
    Jan 2009
    Norwalk, Ohio
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    Never worked on a diesel, but on my 01 s10' we had to lower the transmission down to get the lines off. Bought the oem pre bent lines through rockauto for $42.00 shipped for both.

    You could also do AN fittings, and stainless steel lines as pictured below. This is the setup that I did on my 04' Colorado, Summit Racing carries all the necessary fittings. I did both lines front to back for under $100.00, and you can do it all in your garage with no fancy tools required.

    Click image for larger version. 

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    2004 Chevy Colorado
    LS1 5.7 swap/TBSS rear axle swap

  5. #5
    Sr. Engineer nickgiacalone's Avatar
    Join Date
    Mar 2009
    Metro Detroit, MI


    It's not a diesel, 6.0 Vortec.

  6. #6


    Have you determined where the leak is on the lines? I am asking because mine developed a mild drip, too -- right where the rubber hose changes to a hard metal tube. My tranny mech was supposed to fix that, last week, but it looks like he did the feed from the tranny cooler to the hose and not the hose/hard line combo that runs under the truck to the tranny. I'm going to see him, Monday, for others reasons ... but through I'd chime in to see if your issue was in the same spot as mine. (I don't know how common it is, but it's annoying.)

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