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Limp mode occurred because of leaking trans cooler line

Jwh91

Full Member
Joined
Mar 30, 2018
Messages
40
Hi so the main thing that happened was my wife and I were on the way to the hospital for her scheduled C-section for our second daughter and the check engine light came on in the truck and wouldnt shift past second gear. I took the truck over to O'Reillys,  The code stated the factor was transmission slippage I limped it back home what  was found was my transmission cooler line the feed line was leaking my whole passenger side wheel well was soaked would a leaking line specifically throw that transmission slippage code,  or something else going on ?  It's a 2005 avalanche LT
 
how much fluid did you lose?
OR

How much did you have to add to bring to full mark?
 
A couple of months ago, one of the transmission cooler lines blew off of my transmission as I was driving at full highway speed.

First indication I got was a huge cloud of smoke trailing behind me and blocking my vision of all of the other vehicles behind me on the interstate highway.

I quickly made a bee line for the right hand shoulder of the highway to assess the situation.

When I looked under the passenger side of the truck, the entire underside was covered in some kind of oil.

I had the truck towed to my mechanic's shop.

The next day, they had to have the truck dragged into the lift bay since it could not move under it's own power.

It was determined that the cooler line had disconnected somehow from it's port on the side of the transmission.

They reconnected the line and made sure it was seated firmly and properly.

I went ahead and had them drop the pan and replace the filter and top off the transmission fluid.

This amounted to nothing more than an unscheduled transmission fluid and filter service for my truck.

My last transmission rebuild was 6 years and 100K miles ago.

This event was several thousands of miles ago including a long vacation trip down to the Gulf Coast.

I am seeing no ill effects, so far.

(y)
 
I finally got under the truck. I must still have quite a bit of fluid it will shift to second in drive but it struggles in reverse. I checked all the lines, they are mainly dry and seated properly. I'm not seeing any fluid under the transmission cooler on the chassis but I am under the radiator cooling fan area and that's where it leaks down to the ground. Does the transmission cooler feed into the radiator? I can't tell without taking the front end off which I plan to do anyways just didn't have the time yesterday
 
Transmission cooler is in the radiator.  Lines are accessible on engine side of the radiator, passenger side.  It is possible that your truck also has an auxiliary cooler as well.

Don't keep testing your transmission until you get your fluid level right.  Hopefully all will be well when the fluid is at proper level.  I loaned my truck out and it had a slow fluid line leak.  When I first drove the truck after getting it back it was slipping in 3rd and 4th gear.  Transmission is currently blown apart in my garage.  3/4 steels show signs of over heating.
 
Found the culprit, the cooler lines were dry on the cooler itself but the section where the metal line meets the rubber hose has dry rot and that's where the Leak is, trying to fix the section of line. If it fails I'll just buy new ones, they are $24.99 a piece
 
My truck has been leaking fluid in the exact same spot as yours for years...right where the rubber and metal connect.  Sometimes it leaks, other times it somehow seals itself and wont leak for months.  I'm also confused what fluid is exactly leaking...is it coolant or tranny fluid?  The tranny lines run from the tranny to the radiator then back to tranny.  Is this considered an auxiliary tranny cooler?  My truck is at the dealer currently for numerous other things but they quoted me $489 including labor to fix it...i assume it's for both lines.
 
HAWG WILD said:
...  The tranny lines run from the tranny to the radiator then back to tranny.  Is this considered an auxiliary tranny cooler?  ...

No.

The auxiliary cooler sits horizontally in front center of the radiator and can be clearly seen by looking through the front grill.

The transmission fluid runs from the transmission to the built in cooler in the passenger side tank of the radiator, then it passes forward to the auxiliary cooler and then back to the transmission.

The much smaller, vertical cooler mounted in the driver's side front of the radiator is the power steering fluid cooler.
 
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