Refrigerant in trans oil

[Brian Hains]

I had a transmission flush on my 2018 6L80 at the dealer. Had convertor shudder and random shifting problems. After a while could only use manual shift. Back to dealer, they said refrigerant from the condenser is in the fluid. Could the flush have caused the condenser cooler to rupture internally, causing this?

[rav3]

I guess it's always possible but I have not heard of this in the past. In either case, I don't think the dealer would admit it.

[Snowcamo]

Smh

[txab]

Yo sure the word used wasn't coolant?

[Brian Hains]

No, refrigzrant. The cooler lines go thru the condenser.

[Brian Hains]

1 hour ago, txab said:

Yo sure the word used wasn't coolant?

 

1 hour ago, Snowcamo said:

Smh

Im not big on initials. What do you mean?

[rav3]

On our 2017 Silverado, the transmission cooler lines go to the AC condenser, which serves as the primary heat exchanger for the transmission fluid, with the lines running to the top portion of the condenser to cool the fluid. While some radiators have an integrated cooler, GM vehicles from this era are designed with the transmission cooler built into the A/C condenser.

[Snowcamo]

1 hour ago, Brian Hains said:

 

Im not big on initials. What do you mean?

Shaking my head

 

Like man thats messed up- while shaking my head in sorrow...

[kickass audio]

i'm calling BS on this. It's only possible to have engine coolant contaminate the trans fluid since the first part of the passage in that era truck will have the trans line run through a warming tube on the side cap of the radiator that cools the engine coolant before it then passes onto the secondary radiator that has 100% isolated chambers for the air conditioner condenser and aux trans cooler.

 

I know 100% this is the design as I had a leak in the AC condenser and had to replace the condenser and aux trans cooler. On my 2014 the upper portion of the setup, maybe like the first 4 inches from the top, are a bit thicker for the passageways that connect to the fins on the radiator to dissipate heat and it had a totally separate connection that was tack welded to try and make it one assembly for removal/installation. At no time does the trans fluid come into contact with the HVAC lines.

 

The newer refresh trucks like my new one have totally separate coolers where the condenser is on it's own and the same for the secondary transmission cooler. The only shared cooling is with the heat tube that runs through one side of the radiator for the engine oil cooler and the transmission cooler before the trans line passes to the secondary radiator for additional cooling.

Edited September 6, 2025 by kickass audio

[JimCost2014]

Soooo, does the dealer have a fix? Did they admit guilt, or are they saying it is a common problem?

[rav3]

I'm not an A/C guy but doesn't the refrigerant become a gas when not compressed? I don't think it's possible. It would evaporate. You might have a little A/C oil mixed and I would also think that the A/C system could be contaminated with ATF. Not good. I would have a new condenser & filter installed, flush & recharge A/C.  Then flush the transmission, install new transmission filter & see what happens. 

Good luck getting the dealer to eat that one.

[JC702]

Having replaced the ac condenser in the 2014 Sierra I used to drive I know the condenser is also the trans cooler so there could be some validity to this BUT I would have to ask how they came to this conclusion since refrigerant is a gas which would leave no evidence of intermixing with a liquid like trans fluid that i know of.

 

My old condenser had a small pin hole leak that would cause the AC to blow warm air about a week after recharging it. 

If this diagnosis were accurate, I would think you would have experienced warm AC before any trans symptoms became evident. .