XT5 dark trans fluid drained at 31k mi

[Big O Dave]

This is my Cadillac XT5 with a 9T50 transmission and a LSY 2.0L TGDI engine.

I bought it used when it had 21,500 miles on it, back in October of last year.

My plan has been to do drain and fills at approximately 30,000 mile intervals but the technician who did the drain and fill said that the fluid looked almost black. He can’t smell, so he couldn’t comment on that.

I am alarmed because both the previous owner and I are relatively gentle drivers, but I live near the top of a mountain and have to ascend steep grades on the interstate on a regular basis.

After this recent fluid change I switched the dash readout to transmission fluid temperature as I drove home and on the flat section of the highway it was 205F - 209F and then it went up to 216F on the steep 6% grade.

The ambient temperature range was 105F - 107F.

The shop used dealer-sourced DexVI.

I’m seriously considering doing another drain and fill after 5,000 miles and switching to Valvoline Restore and Protect ATF, doing a double dump to get closer to 100% fluid change.

From that point I’ll go 20,000 miles and see how the fluid has held up at that drain and fill. At that point I’ll decide what interval I should use going forward.

Thoughts, please!

 

[Boomer]

I had a friend who had an Odyssey van that did this. He switched to Mobil 1 ATF and then still changed it every 15,000 miles. That thing ate ATF for lunch.

 

[burbguy82]

If there is a filter I would change it. Dont go over bored with the drain and fill.

 

[pbm]

I'd try Redline D6 ATF and see if it holds up better....expensive but very good.
I plan on using it next in my Ford's 6F35 as I near 100K.

 

[cptbarkey]

Other than the color, which you didn’t know until you drained it, what led you to drain the fluid?

 

[BobsArmory]

Just a couple thoughts.

The color doesn't always match the condition of the fluid. Some just get darker after heating up a few times.
You didn't actually see the oil? The tech may have fishermans disease (I once caught a fish this big!) or he may want you to think he just barely saved you from calamity. So many unknowns at this time.

 

[Marcozi]

Can you recover some of the old fluid? If you can have the old fluid undergo a UOA.

 

[JeffKeryk]

Service that bad boy every 30K. Maybe so 1 at the next oil change services as well...

 

[Sequoiasoon]

Is there a transmission cooler in bottom of radiator like some vehicles? Are there cooler lines going from a hockey puck style back to tranny?

Quick search shows a towing package option that had other cooler options. Maybe you can add an aftermarket version in line or get factory stuff.

 

[martinq]

I like your plan. I would drop the pan for cleaning and to add some magnets but I think 2-3 drain & fills is a good start. R&P ATF is what I would use if it was available in Canada.

 

[Big O Dave]

My original plan, when I bought the car at 21,500 miles, was to do a drain and fill at 30,000 miles, and then every 30,000 miles thereafter.

I came up with that plan because I had done research and found that this trans does not have a serviceable filter. The pan is vertical, so essentially nothing is held in it by gravity. It has a drain plug at the bottom, a fill port at the top, and a fluid level plug on the side. It's set up for doing drain and fills.

After hearing the tech describe the drained-out fluid, I decided to alter my original plan to 20,000 mile intervals. Then, I started to explore changing fluids entirely, which is when I decided to go to VRP ATF. When I switch to that, I want to do two drain/fills back-to-back to get the fluid in the trans closer to 100% VRP ATF. Then I was thinking of doing another short (20,000) interval with VRP ATF to see how that higher quality fluid does, and if it does well, then I'll go back to 30,000 mile intervals.

Is that close to what you guys are saying? I really appreciate all of your suggestions!

 

[Big O Dave]

I like your plan. I would drop the pan for cleaning and to add some magnets but I think 2-3 drain & fills is a good start. R&P ATF is what I would use if it was available in Canada.

After reading your post I then looked into it more and found that Valvoline indeed recommends three back to back drain/fills at the start of using VRP ATF. I’m going to run the existing DexVI through this engine OCI and then switch to the VRP ATF at the same time I change the engine oil.

 

[barkingspider]

I would replace the trans filter before switching to VRP ATF.

 

[martinq]

I remember seeing these AT before with the vertical (plastic?) pan. I'm guessing there are no accessible magnets to service, is there one on the drain plug?

I would look to adding a magnetic, in-line filter like a Magnefine or similar if there are accessible transmission cooling / warming hoses.

 

[nascarnation]

I've written this many times on here and I'll repeat it. These new transmissions run in lockup most of the time, have lots of ratio coverage, and small steps between the ratios. There's no reason they should run hot. The goal is to have them run at least at engine coolant temp for reduced spin loss but that's a zone where fluid is very long lived. Also I think these Dex VI fluids are group III base.

 

[Big O Dave]

I've written this many times on here and I'll repeat it. These new transmissions run in lockup most of the time, have lots of ratio coverage, and small steps between the ratios. There's no reason they should run hot. The goal is to have them run at least at engine coolant temp for reduced spin loss but that's a zone where fluid is very long lived. Also I think these Dex VI fluids are group III base.

Three questions, please:

1. Is dealer-sourced DexVI an average or below average fluid?

2. Should it be able to withstand temperatures in the 210 - 220F range routinely?

3. Is it indeed a problem for it to turn almost black in normal use during a 30,000 mile interval?

 

[Big O Dave]

I remember seeing these AT before with the vertical (plastic?) pan. I'm guessing there are no accessible magnets to service, is there one on the drain plug?

I would look to adding a magnetic, in-line filter like a Magnefine or similar if there are accessible transmission cooling / warming hoses.

I will look into this. Thanks!

 

[Big O Dave]

I would replace the trans filter before switching to VRP ATF.

It’s non-serviceable without significant disassembly, unfortunately.

 

[Big O Dave]

Is there a transmission cooler in bottom of radiator like some vehicles? Are there cooler lines going from a hockey puck style back to tranny?

Quick search shows a towing package option that had other cooler options. Maybe you can add an aftermarket version in line or get factory stuff.

I will also explore the possibility of adding an external cooler. Thanks!

 

[Mcbeem5]

THE SPECS ON DEXRON VI look pretty good,on my truck it gets slightly dark after 30,000 miles

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GM’s DEXRON‑VI spec (GMN10060 / GMW16444) defines a low‑viscosity, long‑life ATF with strict limits on viscosity, friction durability, oxidation stability, and cold‑temperature performance.

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• Kinematic viscosity @ 40°C: ~28.5–29.8 cSt
• Kinematic viscosity @ 100°C: ~5.8–6.0 cSt
• Viscosity Index: 150–151
• Brookfield viscosity @ –40°C: ~10,300–12,030 cP

​

• Pour point: ~–51 to –54°C
• Flash point: 206–220°C
• Density @ 15°C: ~0.846 kg/L
• Sulfated ash: ~0.02%

​

• Improved oxidation stability vs. DEXRON‑III
• Superior shear stability (maintains viscosity under load)
• Enhanced friction durability for smooth shifts and anti‑shudder
• Outstanding low‑temperature fluidity
• Resistance to sludge and deposits
• Compatibility with modern electronic‑control hydraulic circuits (inferred from low‑viscosity and cold‑flow requirements)

​

• Required for 2006+ GM Hydra‑Matic transmissions, including 6L80

​

Property	Typical Value	Source
Viscosity @ 40°C	28.5–29.8 cSt
Viscosity @ 100°C	5.8–6.0 cSt
Viscosity Index	150–151
Brookfield @ –40°C	10,300–12,030 cP
Pour Point	–51 to –54°C
Flash Point	206–220°C
Density @ 15°C	~0.846 kg/L
Sulfated Ash	0.02%