Transmission fluid in Oil 2008 GMC Yukon XL

[Tcox69]

Hello Yukon XL owners,

I have a 2008 GMC Yukon XL 5.3L V8 with 227k miles. About 3,000 miles ago I was at a red light and my dash said to turn off the vehicle immediately because oil pressure was dangerously low. I pulled over and checked oil level which was fine but it he oil dipstick had red fluid on it(presumably ATF). I got it towed to the shop. They said someone had mistakenly added transmission fluid in the oil spout on the engine block(which I did not do). They did an oil change and said come back if you have any further issues. I kept checking the oil every time I filled gas and never saw any red tint on the oil dipstick (just would do drives around town to work etc.) until… Sure enough about 2,000 miles into my oil change I went on a 200 mile road trip and checked the oil dipstick to find red oil. I added 1 quart of oil to the oil spout and 1/4 of a quart of transmission fluid to the Transmission fluid spout. The car drove fine all 200 miles home and back to the shop. Once the shop took another look, they insisted again that I had mistakenly put transmission fluid in the oil spout. Again I did not. Any ideas what could be causing this mix of ATF and Oil and how to fix? I am thinking to replace the Auxiliary Oil/transmission fluid cooler. Open to other ideas. Photos are from the oil change at the shop and the oil dipstick halfway into my road trip.

 

[rdezs]

There's nowhere for them to mix. Other than pouring it directly in the engine.

Oil cooler and transmission cooler are at opposite ends of the radiator. Even if both were leaking inside you have both your engine and transmission with coolant in them.

 

[Tcox69]

There's nowhere for them to mix. Other than pouring it directly in the engine.

Oil cooler and transmission cooler are at opposite ends of the radiator. Even if both were leaking inside you have both your engine and transmission with coolant in them.

I have been reading some people saying that sometimes Mobil 1 Extended life oil can turn red after a couple thousand miles of use. Maybe it is that?

 

[Fless]

You might think about sending a sample to Blackstone or another place for oil analysis.

Oil Analysis | Blackstone Laboratories

Learn what's going on in your engine with oil analysis. Our free kits are easy to use and we explain the results in plain English! Since 1985.

www.blackstone-labs.com

 

[Doubeleive]

Hello Yukon XL owners,

I have a 2008 GMC Yukon XL 5.3L V8 with 227k miles. About 3,000 miles ago I was at a red light and my dash said to turn off the vehicle immediately because oil pressure was dangerously low. I pulled over and checked oil level which was fine but it he oil dipstick had red fluid on it(presumably ATF). I got it towed to the shop. They said someone had mistakenly added transmission fluid in the oil spout on the engine block(which I did not do). They did an oil change and said come back if you have any further issues. I kept checking the oil every time I filled gas and never saw any red tint on the oil dipstick (just would do drives around town to work etc.) until… Sure enough about 2,000 miles into my oil change I went on a 200 mile road trip and checked the oil dipstick to find red oil. I added 1 quart of oil to the oil spout and 1/4 of a quart of transmission fluid to the Transmission fluid spout. The car drove fine all 200 miles home and back to the shop. Once the shop took another look, they insisted again that I had mistakenly put transmission fluid in the oil spout. Again I did not. Any ideas what could be causing this mix of ATF and Oil and how to fix? I am thinking to replace the Auxiliary Oil/transmission fluid cooler. Open to other ideas. Photos are from the oil change at the shop and the oil dipstick halfway into my road trip.

there is no physical connection of the transmission fluid and engine oil
there is a possibility of coolant mixing with the oil, but that generally makes a milk shake, smoke out the tail pipe. there would be telltale signs under the oil fill cap, looking like nose snot, overheating.
eventually the spark plugs wires would melt and you would look like puff the magic dragon driving down the road.

 

[Doubeleive]

AND JUST FOR CLARIFICATION

 

[Marky Dissod]

I have been reading some people saying that sometimes Mobil 1 Extended Life oil can turn red after a couple thousand miles of use. Maybe it is that?

Maybe you get a Used Oil Analysis, then there are no 'maybes' left to wonder & fret over.
Plus the rest of us would all appreciate the DATA as opposed to ... less-than-data.

SPEEDiagnostix - Express Oil Analysis

Spot engine problems early before they become really expensive! Used oil analysis with SPEEDiagnostix is the quickest way to know the health of your engine! Get a detailed report of your motor oil with easy color coded results, along with comments written in plain English by a Certified...

www.speediagnostix.com

 

[07burban88]

this is a long shot, but could the rear main be blown out and the crank case pulling transmission fluid in from the torque converter seal? i mean its the only thing to make sense as its the only possible area for them to meet

 

[rdezs]

this is a long shot, but could the rear main be blown out and the crank case pulling transmission fluid in from the torque converter seal? i mean its the only thing to make sense as its the only possible area for them to meet

No.

Only contact between engine and torque converter is 3 bolts between flex plate and torque converter mounting tabs. No seals, nothing with fluid to exchange. If either was leaking, there would be a puddle underneath....but neither would exchange between engine/trans.

 

[strutaeng]

this is a long shot, but could the rear main be blown out and the crank case pulling transmission fluid in from the torque converter seal? i mean its the only thing to make sense as its the only possible area for them to meet

When the engine rear main seals start leaking, the leaks is external (presumably due to the engine oil pressure pushing oil outside the crankshaft flange.) The drips get flung out inside the bell housing.

I think if you were to have a transmission front pump seal leak, the ATF drip would drip into the torque converter and get flung into the bell housing. Those types of leaks are pretty rare though, I don't even remember reading anyone here on the forum with this type of leak since I joined...

So no, I think that would physically have almost a zero chance the ATF fluid would get into the engine crankcase.

 

[Joseph Garcia]

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics of the truck, please. If we can't see it, it does not exist.

You are already receiving sage advice from the knowledgeable folks on this Forum.

The general consensus here is to get your oil analyzed, and then you will be sure of what's in it. I concur.