Transmission oil leak - what part is it leaking from ?

Eswaroop · July 8

Hi I have a 2024 GMC sierra 2500 HD with 5k miles on it - was under the truck to look for something and noticed that there’s red fluid leaking from this component - not sure what it is but looks like some sort of transmission sensor or valve ?

newdude · July 8

18 minutes ago, Eswaroop said:

Hi I have a 2024 GMC sierra 2500 HD with 5k miles on it - was under the truck to look for something and noticed that there’s red fluid leaking from this component - not sure what it is but looks like some sort of transmission sensor or valve ?

6.6 gas or 6.6 diesel?

newdude · July 8

22 minutes ago, Eswaroop said:

Hi I have a 2024 GMC sierra 2500 HD with 5k miles on it - was under the truck to look for something and noticed that there’s red fluid leaking from this component - not sure what it is but looks like some sort of transmission sensor or valve ?

Nevermind. 6.6 Duramax. That's the fuel cooler. You are seeing either diesel fuel or engine coolant (or a combo of both) leaking.

Eswaroop · July 8

Duramax - correct - Ugh that’s not good is it - mixing coolant with fuel.. it’s gummy so I’m guessing both are leaking but I don’t smell any diesel so it might be just the coolant. I have to say though - the fluid I see looks too thick to be coolant - almost a transmission oil consistency

Eswaroop · July 8

Ok on further inspection looks like the transmission fluid is leaking from the axle next to the fuel cooler and getting sprayed on to the cooler - is that a possibility ? There’s a slight bit of oil on the shaft

Edited July 8 by Eswaroop

newdude · July 10

On 7/8/2024 at 5:15 PM, Eswaroop said:

Ok on further inspection looks like the transmission fluid is leaking from the axle next to the fuel cooler and getting sprayed on to the cooler - is that a possibility ? There’s a slight bit of oil on the shaft

The piece the arrow is coming from, that's the transfer case. Looks like the output side going to the front drive shaft. Transmission would be in front of the transfer case.

Eswaroop · July 11

On 7/10/2024 at 2:40 PM, newdude said:

Hmm ok so the output side shaft going to the front is leaking at the transfer case.. is that the same fluid as the transmission ? Are they connected or will I run out of fluid fairly soon with that leak ( if transfer case is isolated )

The piece the arrow is coming from, that's the transfer case. Looks like the output side going to the front drive shaft. Transmission would be in front of the transfer case.

newdude · July 13

On 7/11/2024 at 4:18 PM, Eswaroop said:

There are two seals, one on the tcase input from the transmission, and one on the transmission side where they bolt up together. Transmission takes Dexron ULV, transfer case takes Dexron 6, so two different fluids.

Either way it sounds like a trip to the dealer for some UV tracer dye added to the transfer case and have it leak tested. If the t-case has no dye anywhere outside it, then they should add some to the transmission. Warranty time.