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Thread: Transmission cooler lines - leaking AGAIN

  1. #21
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    Quote Originally Posted by conway View Post
    I am curious if the leaking cooler lines can be pinpointed to 6 speed trannys and ones that have had work done on them (e.g. TransGo Jr.). I understand that the phenomenon strikes newer trucks so maybe the six speed trannys have a slightly higher pressure that is causing the crimp to let go.
    My transmission is completely stock...
    2007 GMC 2500HD LBZ, 4X4, CC, SB

  2. #22
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    Quote Originally Posted by KenR View Post
    I dunno - Mine started leaking again right when the weather started cooling off a bit, but I wasn't idling the truck any more than usual.
    IIRC, it had something to do with the convertor locking up while in neutral and the tranmission cold mode to help warm things up quicker on cold starts.
    An Allison engineer and I were talking about this during a traning session last winter. But I can't recall the whole explaination he gave me. It was more then just poor quality lines though.

  3. #23
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    Quote Originally Posted by madmatt View Post
    IIRC, it had something to do with the convertor locking up while in neutral and the tranmission cold mode to help warm things up quicker on cold starts.
    Hmmmm. This is interesting....And counterintuitive. During the cold mode (warm up mode), the TC remains open to expedite transmission fluid warming. The open converter allows for more fluid friction. Locking the converter would reduce this effect. Although there is very little TC resistance in neutral, it is still more than none.

    An Allison engineer and I were talking about this during a traning session last winter. But I can't recall the whole explaination he gave me. It was more then just poor quality lines though.
    Poor line quality. The line components are capable of handling significantly more pressure than the tranny will ever produce. The failure is at the crimps, lending to the likelihood of a question of quality. This isn't new. 6.5/2L oil cooler lines saw the same process. GM went cheap with the lines. Simple as that.

    Although we shouldn't have to mess with this, the best solution is to just replace the crimp connection with a known quality repair. I recommend using Aeroquip type hose fittings, with a flare on the line. It is not expensive to do (you can do it yourself, or have any speed shop or AG supplier do it), and will never have this problem if done correctly. A second option is the same for 6.2/5L oil cooler lines. Remove the crimp collar and use hose clamps on the barb. Less permanent, IMO, but better than continually replacing the lines waiting for GM to get it right.
    1985 Blazer 6.2
    2001 GMC 2500HD D/A
    dmaxmaverick@thedieselpage.com

  4. #24
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    Just curious...does anyone know what the maximum pressure the transmission cooler lines will ever see?
    2007 GMC 2500HD LBZ, 4X4, CC, SB

  5. #25
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    Quote Originally Posted by DmaxMaverick View Post
    ...A second option is the same for 6.2/5L oil cooler lines. Remove the crimp collar and use hose clamps on the barb. Less permanent, IMO, but better than continually replacing the lines waiting for GM to get it right.
    I dunno about that. I did EXACTLY that on my wife's LeSabre. Lasted for about a year, then blew off. AFTER fixing on the side of the road, I 'permanently' fixed it by re-clamping and WIRING both sides so they can't pull apart.

    Then I sold it...
    Scott
    St. Louis, MO


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  6. #26
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    Quote Originally Posted by Stlheadake View Post
    I dunno about that. I did EXACTLY that on my wife's LeSabre. Lasted for about a year, then blew off. AFTER fixing on the side of the road, I 'permanently' fixed it by re-clamping and WIRING both sides so they can't pull apart.

    Then I sold it...
    I've done the same fix (with two clamps side by side on each barb) on my daughters Saturn and Wife's Impala .. haven't had one come off yet but I still keep checking them frequently for any signs of seepage ... Several years ago I used the double clamp fix on a low side AC line for my 85 golf diesel.. a new line from the the dealer was over $100 .. I evacuated and recharged the system and it was still working when I sold the car a few years later..
    Bill
    03 2500HD D/A CC/SB/4WD,OilGuard, MegaFilter,LiftPump/PreFilter, Bilsteins,RetraxRollTop,J&J Boards,Coolant Filter,AlliDeepPan,FastIdle,AllHeadLightsOn,
    98 K3500 6.5,SOLD

  7. #27
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    So here's my attempt at a fix...

    First I used a tube cutter to cut the tubing as close to the hose crimps as possible to get the hose section out of the line.



    Then I went to town and got a piece of braided hydraulic hose made up with compression fittings. And just for the record, I was told these compression fittings are supposed to be able to handle 3000 psi or more, as they are regularly used with agricultural equipment. Thats what the guy at the parts store tells me anyways.





    And here it is just loosely assembled, I won't tighten the fittings up until its all in place and fits properly into the truck.



    I hope these work, well I'm quite positive they will hold, I just hope they fit in properly. I just need to go to a hunting store and get a wire brush for cleaning shotguns and scrub out the new hydraulic hose to make sure I get the loose bits out of it. Shortly after I install them, I will be taking my truck to the dealer for transmission service.

    I do have another line to do, just took pictures of the one though.
    2011 VW Jetta TDI, pretty well loaded without leather.
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  8. #28
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    Looks Great .. excellent idea!
    Bill
    03 2500HD D/A CC/SB/4WD,OilGuard, MegaFilter,LiftPump/PreFilter, Bilsteins,RetraxRollTop,J&J Boards,Coolant Filter,AlliDeepPan,FastIdle,AllHeadLightsOn,
    98 K3500 6.5,SOLD

  9. #29

    Default Transmission Lines

    Excellent job, great photos. Please update and let us know how it is progressing.

    Splitrimz
    1994 C3500 6.5TD CREWCAB DUALLY, Heath Turbomaster, cone style cold air intake, PMD cooler mounted under grill, Banks boost and exhaust temp gauges, OPS bypass, Air Lift rear bags.

    2006 LBZ LTD, 4WD, CREW CAB DUALLY.

  10. #30
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    +1. I need to do a permanent fix for mine and like the way this looks.

    Ambient temps here have warmed up a bit and my leaks are not nearly as bad. (Before you ask, yes, I did check the fluid level). Drove the truck to Vegas this week where it was in the 60's and had no leaks at all. I think the cold temperature theory has legs.
    2007 GMC 2500HD LBZ, 4X4, CC, SB

  11. #31
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    Any reason you didn't go with flare fittings? Seems to me the aluminum tubing is the softest thing in the mix, which, I'd think, would make flares preferable to compression fittings.
    The Constitution needs to be re-read, not re-written!

    If you can't handle Dr. Seuss, how will you handle real life?

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  12. #32
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    Quote Originally Posted by JohnC View Post
    Any reason you didn't go with flare fittings? Seems to me the aluminum tubing is the softest thing in the mix, which, I'd think, would make flares preferable to compression fittings.
    This is why I remain skeptical. The fittings are certainly rated and capable of 3,000 PSI. That is, if they are used with compatible line, which should be annealed steel tubing. Using compression fittings on aluminum lines (or soft steel) in a high-vibration application (like anything automotive) is not advisable. Swaged or flare fittings are always the preferred method in this case. It looks good, but I think it'll leak, and perhaps be worse than the current option from GM. I'd be concerned with a blow-out, compared to the minimal leak you are having now.
    1985 Blazer 6.2
    2001 GMC 2500HD D/A
    dmaxmaverick@thedieselpage.com

  13. #33
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    Quote Originally Posted by KenR View Post
    I think the cold temperature theory has legs.
    I have heard GM issued a bulletin last year relative to leaky transmission lines on our trucks, specifically identifying 2006-2009 model year vehicles. Within that bulletin, they indicate the concern (line leaks) are more prevalent in the cold.

    GM released new transmission lines in service that are supposed to be better than the old ones.

    20759971 - Pipe Assy, Upper / outlet ($28.07)
    20759972 - Pipe Assy, Lower / inlet ($25.60)
    20759973 - Hose Assy, Trans Fluid Aux Inlet ($20.46)

    My 2006 has developed a line leak with 45k miles on it. I went around the bush with the stealership yesterday about this and the service manager said the best they can do is get GM to pay for the parts if I pay the estimated $270 to R&R the effected lines. What a deal (sarchasm)... I suspect the dealer was going to eat the cost of the line/s just to get some billable labor on the clock.

    Funny how a powertrain leak isn't covered by a powertrain warranty... but hey, they finally 'fixed' my intermediate steering shaft the 4'th time in for the same issue. If this is the way of 'the new GM', my `06 was my last new GM purchase.

  14. #34
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    Would you know if those part #s are good for an 07 Classic
    Barry USN (Ret)
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  15. #35
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    Quote Originally Posted by mmcm267 View Post
    Would you know if those part #s are good for an 07 Classic
    As far as I know, the part numbers I listed should work for 06-09 model year trucks. The prices I have listed are stealership cost, so expect a hefty markup if calling your local parts department. Or you can get them for the indicated price at gmpartsdirect, if you pay shipping and don't mind waiting until they get around to shipping them out. I had one order from gmpartsdirect take about 3 months to show up last year; luckily I wasn't in a hurry for the parts and (for what it's worth) you're better off using a Ouija board to figure out when the stuff will show up because if you call them you pretty much get the "It will get there when it gets there" response.

    IF any of you guys have the stealership do the work on your rig, make sure they use these part numbers and NOT the previous vintage lines. Sometimes changes go through where dealer inventory of old / obsolete stock can be exhausted before they start using the replacement part. If they use the old / obsolete part, you'll just find yourself going back to the well later to do it all over again...

  16. #36
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    Quote Originally Posted by Quack_Addict View Post

    Funny how a powertrain leak isn't covered by a powertrain warranty... but hey, they finally 'fixed' my intermediate steering shaft the 4'th time in for the same issue. If this is the way of 'the new GM', my `06 was my last new GM purchase.
    I was FURIOUS when I had mine in the shop for this two years ago. Less than 20K on the thing and the lines were leaking! The lines are 'consumable' and therefore not covered was the story I got.

    Almost $600 bucks for the fix (THAT I SHOULD HAVE DONE MYSELF). If it wouldn't have been in the 20's outside, I'd have done it myself! Fortunately mine aren't leaking (YET!). My buddy has an 06, and his were leaking when he bought it last year. They were replaced then. They are leaking again. I'm going to give him those numbers so he can make sure that they are fixed 'correctly', or at least with the correct parts.
    Scott
    St. Louis, MO


    '06 Silverado K2500 4x4 Crew Cab D/A "Big Max" AmpResearch retractable Running Boards, 4" Turbo back Kennedy Exhaust, Kennedy Custom Tune!
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  17. #37
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    The lines are steel of some sort, magnet sticks to them anyways, so I'm not too scared of using the compression fittings.

    I've used these compression fittings before on higher pressure lines, they work well for agricultural equipment so I know they will hold the pressure and vibration.

    One other fix, as recommended by an aircraft mechanic, was to weld a JIC fitting onto the tubing and then simply have a couple short hoses made up with the appropriate fittings.

    I have not put them on my truck yet, waiting until the next oil change. Then shortly after I am taking my truck in for tranny fluid/filter change.
    2011 VW Jetta TDI, pretty well loaded without leather.
    2006 GMC Sierra D-max, 4x4, 4 door, bumper, winch, Espar heater, and the HID lights are a nice touch too.....
    1986 GMC 3500, 454 on propane, 4 speed, 4x4, crew cab dually......the welding truck
    1984 Toyota 4x4 pickup, 4.3 V6, 700R4, Toyota t-case.......transforming into 4x4 cage buggy

  18. #38

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    Quote Originally Posted by Quack_Addict View Post
    I have heard GM issued a bulletin last year relative to leaky transmission lines on our trucks, specifically identifying 2006-2009 model year vehicles. Within that bulletin, they indicate the concern (line leaks) are more prevalent in the cold.

    GM released new transmission lines in service that are supposed to be better than the old ones.

    20759971 - Pipe Assy, Upper / outlet ($28.07)
    20759972 - Pipe Assy, Lower / inlet ($25.60)
    20759973 - Hose Assy, Trans Fluid Aux Inlet ($20.46)

    My 2006 has developed a line leak with 45k miles on it......
    Anyone have any pictures of these supposed newer and improved lines?

  19. #39
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    Hell, when are they going to step up and fix them? 500 bucks and mine still leak!!!
    Scott
    St. Louis, MO


    '06 Silverado K2500 4x4 Crew Cab D/A "Big Max" AmpResearch retractable Running Boards, 4" Turbo back Kennedy Exhaust, Kennedy Custom Tune!
    '99 BMW K1200LT "Special K" my other "SUV"
    '07 Salem by Forest River Fifth Wheel Toy Hauler

  20. #40

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    My '06 is leaking - again...
    2011 Chevrolet Tahoe 5.3L daily driver
    • Previous owner of two 1994 6.5L K3500s, '01, '02, and '05 6.6L K2500s, '04 C4500, '06 K3500 dually, '06 K3500 SRW, '09 K3500HD SRW, '05 Denali
    • Total GM diesel miles to date : ~950K

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