Tranny lines leaking

[09avalanche]

Hey folks I recently replaced the rubber parts of my trans lines just behind the rad in front of engine 'cause the originals were wet and looked as though they had been a little leaky plus a spot on driveway.While under the truck I noticed the lines further back where they run towards the trans there was drop or two hanging ready to stain again,so cleaned off, looked good for day then has come back.My thought is could the hardline itself possibly have pinhole in it ,has anyone else experienced this?09 Avalanche 5.3 188,000 kms/120,000mi ish Krown sprayed so in really good rust free overall shape and no that's not what is dripping 'cause it stops days after initial spray,any thoughts appreciated.

[dtnel78]

It's more than likely at the joints in the lines. You could get a dye kit and put dye in the transmission fluid, run it a day, two or whatevers needed then use the glasses and light and go look for the bright leaky spot that'll show where it's coming thru at.


Are the cooler lines a rubber / metal combo as mine on my 04 leak by the radiator and drip down and it blows back. I've had the lines probably 5-6 yrs and still haven't installed them yet but I'll be doing that this early summer.

Have to lean the rear of transmission down some to get fitting loose on top of transmission on my vehicle.

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[MaverickZ71]

GM/AC Delco can't build a cooler line worth a damn to save their soul.  Have had this problem on my last 3 GM vehicles.  On my current daily driver, I'm on my 3rd set of trans cooler lines and oil cooler lines, and they're leaking again.  First they "sweat" at the crimps and then that proceeds to dripping.  No more GM/ACD lines for me.  I've been told that NAPA lines are better or to have custom lines built at a local hydraulic shop.  

[swathdiver]

59 minutes ago, MaverickZ71 said:

GM/AC Delco can't build a cooler line worth a damn to save their soul.  Have had this problem on my last 3 GM vehicles.  On my current daily driver, I'm on my 3rd set of trans cooler lines and oil cooler lines, and they're leaking again.  First they "sweat" at the crimps and then that proceeds to dripping.  No more GM/ACD lines for me.  I've been told that NAPA lines are better or to have custom lines built at a local hydraulic shop.  

Me too, In the 1980s and 1990s the lines lasted about 6-8 years and now mine are eleven years old and only sweating.  Pretty good I'd say.

[09avalanche]

Thank-you all for your feedback,Amazon has ACDelco lines for $146.cdn.,dealer I've read $200.ish,so for sure I'll check out Napa.I'll also look into the dye-job.Your time is appreciated.

[davester]

check rockauto for prices.  I find them to, in general, be WAY cheaper than Canadian sources, even after shipping.  If I can plan ahead of time for a problem, I will order stuff out of the states and save a bundle of money.  And if you use rockauto, don't forget to use their 5% off discount code (google for it).

[09avalanche]

Thank-you davester,be sure to check 'em out.

[CapitalTruck]

Or just cut out the rubber section and use 11/16 trans cooler hose with a couple clamps.  Its worked well for me.